{ "source": "doc/api/all.md", "miscs": [ { "textRaw": "About this Documentation", "name": "About this Documentation", "type": "misc", "desc": "
The goal of this documentation is to comprehensively explain the Node.js\nAPI, both from a reference as well as a conceptual point of view. Each\nsection describes a built-in module or high-level concept.\n\n
\nWhere appropriate, property types, method arguments, and the arguments\nprovided to event handlers are detailed in a list underneath the topic\nheading.\n\n
\nEvery .html
document has a corresponding .json
document presenting\nthe same information in a structured manner. This feature is\nexperimental, and added for the benefit of IDEs and other utilities that\nwish to do programmatic things with the documentation.\n\n
Every .html
and .json
file is generated based on the corresponding\n.md
file in the doc/api/
folder in Node.js's source tree. The\ndocumentation is generated using the tools/doc/generate.js
program.\nThe HTML template is located at doc/template.html
.\n\n\n
If you find a error in this documentation, please [submit an issue][]\nor see [the contributing guide][] for directions on how to submit a patch.\n\n
\n", "miscs": [ { "textRaw": "Stability Index", "name": "Stability Index", "type": "misc", "desc": "Throughout the documentation, you will see indications of a section's\nstability. The Node.js API is still somewhat changing, and as it\nmatures, certain parts are more reliable than others. Some are so\nproven, and so relied upon, that they are unlikely to ever change at\nall. Others are brand new and experimental, or known to be hazardous\nand in the process of being redesigned.\n\n
\nThe stability indices are as follows:\n\n
\nStability: 0 - Deprecated\nThis feature is known to be problematic, and changes are\nplanned. Do not rely on it. Use of the feature may cause warnings. Backwards\ncompatibility should not be expected.
\nStability: 1 - Experimental\nThis feature is subject to change, and is gated by a command line flag.\nIt may change or be removed in future versions.
\nStability: 2 - Stable\nThe API has proven satisfactory. Compatibility with the npm ecosystem\nis a high priority, and will not be broken unless absolutely necessary.
\nStability: 3 - Locked\nOnly fixes related to security, performance, or bug fixes will be accepted.\nPlease do not suggest API changes in this area; they will be refused.
\n"
},
{
"textRaw": "JSON Output",
"name": "json_output",
"stability": 1,
"stabilityText": "Experimental",
"desc": "Every HTML file in the markdown has a corresponding JSON file with the\nsame data.\n\n
\nThis feature was added in Node.js v0.6.12. It is experimental.\n\n
\n", "type": "misc", "displayName": "JSON Output" }, { "textRaw": "Syscalls and man pages", "name": "syscalls_and_man_pages", "desc": "System calls like open(2) and read(2) define the interface between user programs\nand the underlying operating system. Node functions which simply wrap a syscall,\nlike fs.open()
, will document that. The docs link to the corresponding man\npages (short for manual pages) which describe how the syscalls work.\n\n
Caveat: some syscalls, like lchown(2), are BSD-specific. That means, for\nexample, that fs.lchown()
only works on Mac OS X and other BSD-derived systems,\nand is not available on Linux.\n\n
Most Unix syscalls have Windows equivalents, but behavior may differ on Windows\nrelative to Linux and OS X. For an example of the subtle ways in which it's\nsometimes impossible to replace Unix syscall semantics on Windows, see Node\nissue 4760.\n\n
\n", "type": "misc", "displayName": "Syscalls and man pages" } ] }, { "textRaw": "Usage", "name": "Usage", "type": "misc", "desc": "node [options] [v8 options] [script.js | -e "script"] [arguments]
\n\n
Please see the [Command Line Options][] document for information about\ndifferent options and ways to run scripts with Node.js.\n\n
\nAn example of a [web server][] written with Node.js which responds with\n'Hello World'
:\n\n
const http = require('http');\n\nconst hostname = '127.0.0.1';\nconst port = 3000;\n\nconst server = http.createServer((req, res) => {\n res.statusCode = 200;\n res.setHeader('Content-Type', 'text/plain');\n res.end('Hello World\\n');\n});\n\nserver.listen(port, hostname, () => {\n console.log(`Server running at http://${hostname}:${port}/`);\n});
\nTo run the server, put the code into a file called example.js
and execute\nit with Node.js:\n\n
$ node example.js\nServer running at http://127.0.0.1:3000/
\nAll of the examples in the documentation can be run similarly.\n\n
\n" }, { "textRaw": "Command Line Options", "name": "Command Line Options", "type": "misc", "desc": "Node.js comes with a wide variety of CLI options. These options expose built-in\ndebugging, multiple ways to execute scripts, and other helpful runtime options.\n\n
\nTo view this documentation as a manual page in your terminal, run man node
.\n\n\n
node [options] [v8 options] [script.js | -e "script"] [arguments]
\n\n
node debug [script.js | -e "script" | <host>:<port>] …
\n\n
node --v8-options
\n\n
Execute without arguments to start the [REPL][].\n\n
\nFor more info about node debug
, please see the [debugger][] documentation.\n\n\n
Print node's version.\n\n\n
\n", "type": "module", "displayName": "`-v`, `--version`" }, { "textRaw": "`-h`, `--help`", "name": "`-h`,_`--help`", "desc": "Print node command line options.\nThe output of this option is less detailed than this document.\n\n\n
\n", "type": "module", "displayName": "`-h`, `--help`" }, { "textRaw": "`-e`, `--eval \"script\"`", "name": "`-e`,_`--eval_\"script\"`", "desc": "Evaluate the following argument as JavaScript. The modules which are\npredefined in the REPL can also be used in script
.\n\n\n
Identical to -e
but prints the result.\n\n\n
Syntax check the script without executing.\n\n\n
\n", "type": "module", "displayName": "`-c`, `--check`" }, { "textRaw": "`-i`, `--interactive`", "name": "`-i`,_`--interactive`", "desc": "Opens the REPL even if stdin does not appear to be a terminal.\n\n\n
\n", "type": "module", "displayName": "`-i`, `--interactive`" }, { "textRaw": "`-r`, `--require module`", "name": "`-r`,_`--require_module`", "desc": "Preload the specified module at startup.\n\n
\nFollows require()
's module resolution\nrules. module
may be either a path to a file, or a node module name.\n\n\n
Silence deprecation warnings.\n\n\n
\n", "type": "module", "displayName": "`--no-deprecation`" }, { "textRaw": "`--trace-deprecation`", "name": "`--trace-deprecation`", "desc": "Print stack traces for deprecations.\n\n\n
\n", "type": "module", "displayName": "`--trace-deprecation`" }, { "textRaw": "`--throw-deprecation`", "name": "`--throw-deprecation`", "desc": "Throw errors for deprecations.\n\n
\n", "type": "module", "displayName": "`--throw-deprecation`" }, { "textRaw": "`--no-warnings`", "name": "`--no-warnings`", "desc": "Silence all process warnings (including deprecations).\n\n
\n", "type": "module", "displayName": "`--no-warnings`" }, { "textRaw": "`--trace-warnings`", "name": "`--trace-warnings`", "desc": "Print stack traces for process warnings (including deprecations).\n\n
\n", "type": "module", "displayName": "`--trace-warnings`" }, { "textRaw": "`--trace-sync-io`", "name": "`--trace-sync-io`", "desc": "Prints a stack trace whenever synchronous I/O is detected after the first turn\nof the event loop.\n\n\n
\n", "type": "module", "displayName": "`--trace-sync-io`" }, { "textRaw": "`--zero-fill-buffers`", "name": "`--zero-fill-buffers`", "desc": "Automatically zero-fills all newly allocated [Buffer][] and [SlowBuffer][]\ninstances.\n\n\n
\n", "type": "module", "displayName": "`--zero-fill-buffers`" }, { "textRaw": "`--track-heap-objects`", "name": "`--track-heap-objects`", "desc": "Track heap object allocations for heap snapshots.\n\n\n
\n", "type": "module", "displayName": "`--track-heap-objects`" }, { "textRaw": "`--prof-process`", "name": "`--prof-process`", "desc": "Process v8 profiler output generated using the v8 option --prof
.\n\n\n
Print v8 command line options.\n\n\n
\n", "type": "module", "displayName": "`--v8-options`" }, { "textRaw": "`--tls-cipher-list=list`", "name": "`--tls-cipher-list=list`", "desc": "Specify an alternative default TLS cipher list. (Requires Node.js to be built\nwith crypto support. (Default))\n\n\n
\n", "type": "module", "displayName": "`--tls-cipher-list=list`" }, { "textRaw": "`--enable-fips`", "name": "`--enable-fips`", "desc": "Enable FIPS-compliant crypto at startup. (Requires Node.js to be built with\n./configure --openssl-fips
)\n\n\n
Force FIPS-compliant crypto on startup. (Cannot be disabled from script code.)\n(Same requirements as --enable-fips
)\n\n\n
Specify ICU data load path. (overrides NODE_ICU_DATA
)\n\n\n
','
-separated list of core modules that should print debug information.\n\n\n
':'
-separated list of directories prefixed to the module search path.\n\n
Note: on Windows, this is a ';'
-separated list instead.\n\n\n
When set to 1
colors will not be used in the REPL.\n\n\n
Data path for ICU (Intl object) data. Will extend linked-in data when compiled\nwith small-icu support.\n\n\n
\n", "type": "module", "displayName": "`NODE_ICU_DATA=file`" }, { "textRaw": "`NODE_REPL_HISTORY=file`", "name": "`node_repl_history=file`", "desc": "Path to the file used to store the persistent REPL history. The default path is\n~/.node_repl_history
, which is overridden by this variable. Setting the value\nto an empty string (""
or " "
) disables persistent REPL history.\n\n\n
Node.js includes a full-featured out-of-process debugging utility accessible\nvia a simple [TCP-based protocol][] and built-in debugging client. To use it,\nstart Node.js with the debug
argument followed by the path to the script to\ndebug; a prompt will be displayed indicating successful launch of the debugger:\n\n
$ node debug myscript.js\n< debugger listening on port 5858\nconnecting... ok\nbreak in /home/indutny/Code/git/indutny/myscript.js:1\n 1 x = 5;\n 2 setTimeout(() => {\n 3 debugger;\ndebug>
\nNode.js's debugger client does not yet support the full range of commands, but\nsimple step and inspection are possible.\n\n
\nInserting the statement debugger;
into the source code of a script will\nenable a breakpoint at that position in the code.\n\n
For example, suppose myscript.js
is written as:\n\n
// myscript.js\nx = 5;\nsetTimeout(() => {\n debugger;\n console.log('world');\n}, 1000);\nconsole.log('hello');
\nOnce the debugger is run, a breakpoint will occur at line 4:\n\n
\n$ node debug myscript.js\n< debugger listening on port 5858\nconnecting... ok\nbreak in /home/indutny/Code/git/indutny/myscript.js:1\n 1 x = 5;\n 2 setTimeout(() => {\n 3 debugger;\ndebug> cont\n< hello\nbreak in /home/indutny/Code/git/indutny/myscript.js:3\n 1 x = 5;\n 2 setTimeout(() => {\n 3 debugger;\n 4 console.log('world');\n 5 }, 1000);\ndebug> next\nbreak in /home/indutny/Code/git/indutny/myscript.js:4\n 2 setTimeout(() => {\n 3 debugger;\n 4 console.log('world');\n 5 }, 1000);\n 6 console.log('hello');\ndebug> repl\nPress Ctrl + C to leave debug repl\n> x\n5\n> 2+2\n4\ndebug> next\n< world\nbreak in /home/indutny/Code/git/indutny/myscript.js:5\n 3 debugger;\n 4 console.log('world');\n 5 }, 1000);\n 6 console.log('hello');\n 7\ndebug> quit
\nThe repl
command allows code to be evaluated remotely. The next
command\nsteps over to the next line. Type help
to see what other commands are\navailable.\n\n
Pressing enter
without typing a command will repeat the previous debugger\ncommand.\n\n
It is possible to watch expression and variable values while debugging. On\nevery breakpoint, each expression from the watchers list will be evaluated\nin the current context and displayed immediately before the breakpoint's\nsource code listing.\n\n
\nTo begin watching an expression, type watch('my_expression')
. The command\nwatchers
will print the active watchers. To remove a watcher, type\nunwatch('my_expression')
.\n\n
cont
, c
- Continue executionnext
, n
- Step nextstep
, s
- Step inout
, o
- Step outpause
- Pause running code (like pause button in Developer Tools)setBreakpoint()
, sb()
- Set breakpoint on current linesetBreakpoint(line)
, sb(line)
- Set breakpoint on specific linesetBreakpoint('fn()')
, sb(...)
- Set breakpoint on a first statement in\nfunctions bodysetBreakpoint('script.js', 1)
, sb(...)
- Set breakpoint on first line of\nscript.jsclearBreakpoint('script.js', 1)
, cb(...)
- Clear breakpoint in script.js\non line 1It is also possible to set a breakpoint in a file (module) that\nisn't loaded yet:\n\n
\n$ ./node debug test/fixtures/break-in-module/main.js\n< debugger listening on port 5858\nconnecting to port 5858... ok\nbreak in test/fixtures/break-in-module/main.js:1\n 1 var mod = require('./mod.js');\n 2 mod.hello();\n 3 mod.hello();\ndebug> setBreakpoint('mod.js', 23)\nWarning: script 'mod.js' was not loaded yet.\n 1 var mod = require('./mod.js');\n 2 mod.hello();\n 3 mod.hello();\ndebug> c\nbreak in test/fixtures/break-in-module/mod.js:23\n 21\n 22 exports.hello = () => {\n 23 return 'hello from module';\n 24 };\n 25\ndebug>
\n",
"type": "module",
"displayName": "Breakpoints"
},
{
"textRaw": "Execution control",
"name": "Execution control",
"desc": "run
- Run script (automatically runs on debugger's start)restart
- Restart scriptkill
- Kill scriptscripts
- List all loaded scriptsversion
- Display V8's versionAn alternative way of enabling and accessing the debugger is to start\nNode.js with the --debug
command-line flag or by signaling an existing\nNode.js process with SIGUSR1
.\n\n
Once a process has been set in debug mode this way, it can be connected to\nusing the Node.js debugger by either connecting to the pid
of the running\nprocess or via URI reference to the listening debugger:\n\n
node debug -p <pid>
- Connects to the process via the pid
node debug <URI>
- Connects to the process via the URI such as\nlocalhost:5858Applications running in Node.js will generally experience four categories of\nerrors:\n\n
\neval()
fails.assert
module.All JavaScript and System errors raised by Node.js inherit from, or are\ninstances of, the standard JavaScript {Error} class and are guaranteed\nto provide at least the properties available on that class.\n\n
\n", "miscs": [ { "textRaw": "Error Propagation and Interception", "name": "Error Propagation and Interception", "type": "misc", "desc": "Node.js supports several mechanisms for propagating and handling errors that\noccur while an application is running. How these errors are reported and\nhandled depends entirely on the type of Error and the style of the API that is\ncalled.\n\n
\nAll JavaScript errors are handled as exceptions that immediately generate\nand throw an error using the standard JavaScript throw
mechanism. These\nare handled using the [try / catch
construct][try-catch] provided by the JavaScript\nlanguage.\n\n
// Throws with a ReferenceError because z is undefined\ntry {\n const m = 1;\n const n = m + z;\n} catch (err) {\n // Handle the error here.\n}
\nAny use of the JavaScript throw
mechanism will raise an exception that\nmust be handled using try / catch
or the Node.js process will exit\nimmediately.\n\n
With few exceptions, Synchronous APIs (any blocking method that does not\naccept a callback
function, such as [fs.readFileSync
][]), will use throw
\nto report errors.\n\n
Errors that occur within Asynchronous APIs may be reported in multiple ways:\n\n
\nMost asynchronous methods that accept a callback
function will accept an\nError
object passed as the first argument to that function. If that first\nargument is not null
and is an instance of Error
, then an error occurred\nthat should be handled.
const fs = require('fs');\nfs.readFile('a file that does not exist', (err, data) => {\n if (err) {\n console.error('There was an error reading the file!', err);\n return;\n }\n // Otherwise handle the data\n});
\nWhen an asynchronous method is called on an object that is an EventEmitter
,\nerrors can be routed to that object's 'error'
event.
const net = require('net');\nconst connection = net.connect('localhost');\n\n// Adding an 'error' event handler to a stream:\nconnection.on('error', (err) => {\n // If the connection is reset by the server, or if it can't\n // connect at all, or on any sort of error encountered by\n // the connection, the error will be sent here.\n console.error(err);\n});\n\nconnection.pipe(process.stdout);
\nA handful of typically asynchronous methods in the Node.js API may still\nuse the throw
mechanism to raise exceptions that must be handled using\ntry / catch
. There is no comprehensive list of such methods; please\nrefer to the documentation of each method to determine the appropriate\nerror handling mechanism required.
The use of the 'error'
event mechanism is most common for [stream-based][]\nand [event emitter-based][] APIs, which themselves represent a series of\nasynchronous operations over time (as opposed to a single operation that may\npass or fail).\n\n
For all EventEmitter
objects, if an 'error'
event handler is not\nprovided, the error will be thrown, causing the Node.js process to report an\nunhandled exception and crash unless either: The [domain
][domains] module is used\nappropriately or a handler has been registered for the\n[process.on('uncaughtException')
][] event.\n\n
const EventEmitter = require('events');\nconst ee = new EventEmitter();\n\nsetImmediate(() => {\n // This will crash the process because no 'error' event\n // handler has been added.\n ee.emit('error', new Error('This will crash'));\n});
\nErrors generated in this way cannot be intercepted using try / catch
as\nthey are thrown after the calling code has already exited.\n\n
Developers must refer to the documentation for each method to determine\nexactly how errors raised by those methods are propagated.\n\n
\n", "miscs": [ { "textRaw": "Node.js style callbacks", "name": "Node.js style callbacks", "type": "misc", "desc": "Most asynchronous methods exposed by the Node.js core API follow an idiomatic\npattern referred to as a "Node.js style callback". With this pattern, a\ncallback function is passed to the method as an argument. When the operation\neither completes or an error is raised, the callback function is called with\nthe Error object (if any) passed as the first argument. If no error was raised,\nthe first argument will be passed as null
.\n\n
const fs = require('fs');\n\nfunction nodeStyleCallback(err, data) {\n if (err) {\n console.error('There was an error', err);\n return;\n }\n console.log(data);\n}\n\nfs.readFile('/some/file/that/does-not-exist', nodeStyleCallback);\nfs.readFile('/some/file/that/does-exist', nodeStyleCallback)
\nThe JavaScript try / catch
mechanism cannot be used to intercept errors\ngenerated by asynchronous APIs. A common mistake for beginners is to try to\nuse throw
inside a Node.js style callback:\n\n
// THIS WILL NOT WORK:\nconst fs = require('fs');\n\ntry {\n fs.readFile('/some/file/that/does-not-exist', (err, data) => {\n // mistaken assumption: throwing here...\n if (err) {\n throw err;\n }\n });\n} catch(err) {\n // This will not catch the throw!\n console.log(err);\n}
\nThis will not work because the callback function passed to fs.readFile()
is\ncalled asynchronously. By the time the callback has been called, the\nsurrounding code (including the try { } catch(err) { }
block will have\nalready exited. Throwing an error inside the callback can crash the Node.js\nprocess in most cases. If [domains][] are enabled, or a handler has been\nregistered with process.on('uncaughtException')
, such errors can be\nintercepted.\n\n
A JavaScript exception is a value that is thrown as a result of an invalid\noperation or as the target of a throw
statement. While it is not required\nthat these values are instances of Error
or classes which inherit from\nError
, all exceptions thrown by Node.js or the JavaScript runtime will be\ninstances of Error.\n\n
Some exceptions are unrecoverable at the JavaScript layer. Such exceptions\nwill always cause the Node.js process to crash. Examples include assert()
\nchecks or abort()
calls in the C++ layer.\n\n
System errors are generated when exceptions occur within the program's\nruntime environment. Typically, these are operational errors that occur\nwhen an application violates an operating system constraint such as attempting\nto read a file that does not exist or when the user does not have sufficient\npermissions.\n\n
\nSystem errors are typically generated at the syscall level: an exhaustive list\nof error codes and their meanings is available by running man 2 intro
or\nman 3 errno
on most Unices; or [online][].\n\n
In Node.js, system errors are represented as augmented Error
objects with\nadded properties.\n\n
Returns a string representing the error code, which is always E
followed by\na sequence of capital letters, and may be referenced in man 2 intro
.\n\n
The properties error.code
and error.errno
are aliases of one another and\nreturn the same value.\n\n
Returns a string representing the error code, which is always E
followed by\na sequence of capital letters, and may be referenced in man 2 intro
.\n\n
The properties error.code
and error.errno
are aliases of one another and\nreturn the same value.\n\n
Returns a string describing the [syscall][] that failed.\n\n
\n" } ] } ], "modules": [ { "textRaw": "Common System Errors", "name": "common_system_errors", "desc": "This list is not exhaustive, but enumerates many of the common system\nerrors encountered when writing a Node.js program. An exhaustive list may be\nfound [here][online].\n\n
\nEACCES
(Permission denied): An attempt was made to access a file in a way\nforbidden by its file access permissions.
EADDRINUSE
(Address already in use): An attempt to bind a server\n([net
][], [http
][], or [https
][]) to a local address failed due to\nanother server on the local system already occupying that address.
ECONNREFUSED
(Connection refused): No connection could be made because the\ntarget machine actively refused it. This usually results from trying to\nconnect to a service that is inactive on the foreign host.
ECONNRESET
(Connection reset by peer): A connection was forcibly closed by\na peer. This normally results from a loss of the connection on the remote\nsocket due to a timeout or reboot. Commonly encountered via the [http
][]\nand [net
][] modules.
EEXIST
(File exists): An existing file was the target of an operation that\nrequired that the target not exist.
EISDIR
(Is a directory): An operation expected a file, but the given\npathname was a directory.
EMFILE
(Too many open files in system): Maximum number of\n[file descriptors][] allowable on the system has been reached, and\nrequests for another descriptor cannot be fulfilled until at least one\nhas been closed. This is encountered when opening many files at once in\nparallel, especially on systems (in particular, OS X) where there is a low\nfile descriptor limit for processes. To remedy a low limit, run\nulimit -n 2048
in the same shell that will run the Node.js process.
ENOENT
(No such file or directory): Commonly raised by [fs
][] operations\nto indicate that a component of the specified pathname does not exist -- no\nentity (file or directory) could be found by the given path.
ENOTDIR
(Not a directory): A component of the given pathname existed, but\nwas not a directory as expected. Commonly raised by [fs.readdir
][].
ENOTEMPTY
(Directory not empty): A directory with entries was the target\nof an operation that requires an empty directory -- usually [fs.unlink
][].
EPERM
(Operation not permitted): An attempt was made to perform an\noperation that requires elevated privileges.
EPIPE
(Broken pipe): A write on a pipe, socket, or FIFO for which there is\nno process to read the data. Commonly encountered at the [net
][] and\n[http
][] layers, indicative that the remote side of the stream being\nwritten to has been closed.
ETIMEDOUT
(Operation timed out): A connect or send request failed because\nthe connected party did not properly respond after a period of time. Usually\nencountered by [http
][] or [net
][] -- often a sign that a socket.end()
\nwas not properly called.
A generic JavaScript Error
object that does not denote any specific\ncircumstance of why the error occurred. Error
objects capture a "stack trace"\ndetailing the point in the code at which the Error
was instantiated, and may\nprovide a text description of the error.\n\n
All errors generated by Node.js, including all System and JavaScript errors,\nwill either be instances of, or inherit from, the Error
class.\n\n
Creates a .stack
property on targetObject
, which when accessed returns\na string representing the location in the code at which\nError.captureStackTrace()
was called.\n\n
const myObject = {};\nError.captureStackTrace(myObject);\nmyObject.stack // similar to `new Error().stack`
\nThe first line of the trace, instead of being prefixed with ErrorType:\nmessage
, will be the result of calling targetObject.toString()
.\n\n
The optional constructorOpt
argument accepts a function. If given, all frames\nabove constructorOpt
, including constructorOpt
, will be omitted from the\ngenerated stack trace.\n\n
The constructorOpt
argument is useful for hiding implementation\ndetails of error generation from an end user. For instance:\n\n
function MyError() {\n Error.captureStackTrace(this, MyError);\n}\n\n// Without passing MyError to captureStackTrace, the MyError\n// frame would should up in the .stack property. by passing\n// the constructor, we omit that frame and all frames above it.\nnew MyError().stack
\n",
"signatures": [
{
"params": [
{
"name": "targetObject"
},
{
"name": "constructorOpt",
"optional": true
}
]
}
]
}
],
"properties": [
{
"textRaw": "Error.stackTraceLimit",
"name": "stackTraceLimit",
"desc": "The Error.stackTraceLimit
property specifies the number of stack frames\ncollected by a stack trace (whether generated by new Error().stack
or\nError.captureStackTrace(obj)
).\n\n
The default value is 10
but may be set to any valid JavaScript number. Changes\nwill affect any stack trace captured after the value has been changed.\n\n
If set to a non-number value, or set to a negative number, stack traces will\nnot capture any frames.\n\n
\n", "properties": [ { "textRaw": "error.message", "name": "message", "desc": "Returns the string description of error as set by calling new Error(message)
.\nThe message
passed to the constructor will also appear in the first line of\nthe stack trace of the Error
, however changing this property after the\nError
object is created may not change the first line of the stack trace.\n\n
const err = new Error('The message');\nconsole.log(err.message);\n // Prints: The message
\n"
},
{
"textRaw": "error.stack",
"name": "stack",
"desc": "Returns a string describing the point in the code at which the Error
was\ninstantiated.\n\n
For example:\n\n
\nError: Things keep happening!\n at /home/gbusey/file.js:525:2\n at Frobnicator.refrobulate (/home/gbusey/business-logic.js:424:21)\n at Actor.<anonymous> (/home/gbusey/actors.js:400:8)\n at increaseSynergy (/home/gbusey/actors.js:701:6)
\nThe first line is formatted as <error class name>: <error message>
, and\nis followed by a series of stack frames (each line beginning with "at ").\nEach frame describes a call site within the code that lead to the error being\ngenerated. V8 attempts to display a name for each function (by variable name,\nfunction name, or object method name), but occasionally it will not be able to\nfind a suitable name. If V8 cannot determine a name for the function, only\nlocation information will be displayed for that frame. Otherwise, the\ndetermined function name will be displayed with location information appended\nin parentheses.\n\n
It is important to note that frames are only generated for JavaScript\nfunctions. If, for example, execution synchronously passes through a C++ addon\nfunction called cheetahify
, which itself calls a JavaScript function, the\nframe representing the cheetahify
call will not be present in the stack\ntraces:\n\n
const cheetahify = require('./native-binding.node');\n\nfunction makeFaster() {\n // cheetahify *synchronously* calls speedy.\n cheetahify(function speedy() {\n throw new Error('oh no!');\n });\n}\n\nmakeFaster(); // will throw:\n // /home/gbusey/file.js:6\n // throw new Error('oh no!');\n // ^\n // Error: oh no!\n // at speedy (/home/gbusey/file.js:6:11)\n // at makeFaster (/home/gbusey/file.js:5:3)\n // at Object.<anonymous> (/home/gbusey/file.js:10:1)\n // at Module._compile (module.js:456:26)\n // at Object.Module._extensions..js (module.js:474:10)\n // at Module.load (module.js:356:32)\n // at Function.Module._load (module.js:312:12)\n // at Function.Module.runMain (module.js:497:10)\n // at startup (node.js:119:16)\n // at node.js:906:3
\nThe location information will be one of:\n\n
\nnative
, if the frame represents a call internal to V8 (as in [].forEach
).plain-filename.js:line:column
, if the frame represents a call internal\n to Node.js./absolute/path/to/file.js:line:column
, if the frame represents a call in\na user program, or its dependencies.The string representing the stack trace is lazily generated when the\nerror.stack
property is accessed.\n\n
The number of frames captured by the stack trace is bounded by the smaller of\nError.stackTraceLimit
or the number of available frames on the current event\nloop tick.\n\n
System-level errors are generated as augmented Error
instances, which are\ndetailed here.\n\n
Creates a new Error
object and sets the error.message
property to the\nprovided text message. If an object is passed as message
, the text message\nis generated by calling message.toString()
. The error.stack
property will\nrepresent the point in the code at which new Error()
was called. Stack traces\nare dependent on [V8's stack trace API][]. Stack traces extend only to either\n(a) the beginning of synchronous code execution, or (b) the number of frames\ngiven by the property Error.stackTraceLimit
, whichever is smaller.\n\n
A subclass of Error
that indicates that a provided argument was not within the\nset or range of acceptable values for a function; whether that is a numeric\nrange, or outside the set of options for a given function parameter.\n\n
For example:\n\n
\nrequire('net').connect(-1);\n // throws RangeError, port should be > 0 && < 65536
\nNode.js will generate and throw RangeError
instances immediately as a form\nof argument validation.\n\n
A subclass of Error
that indicates that an attempt is being made to access a\nvariable that is not defined. Such errors commonly indicate typos in code, or\nan otherwise broken program.\n\n
While client code may generate and propagate these errors, in practice, only V8\nwill do so.\n\n
\ndoesNotExist;\n // throws ReferenceError, doesNotExist is not a variable in this program.
\nReferenceError
instances will have an error.arguments
property whose value\nis an array containing a single element: a string representing the variable\nthat was not defined.\n\n
const assert = require('assert');\ntry {\n doesNotExist;\n} catch(err) {\n assert(err.arguments[0], 'doesNotExist');\n}
\nUnless an application is dynamically generating and running code,\nReferenceError
instances should always be considered a bug in the code\nor its dependencies.\n\n
A subclass of Error
that indicates that a program is not valid JavaScript.\nThese errors may only be generated and propagated as a result of code\nevaluation. Code evaluation may happen as a result of eval
, Function
,\nrequire
, or [vm][]. These errors are almost always indicative of a broken\nprogram.\n\n
try {\n require('vm').runInThisContext('binary ! isNotOk');\n} catch(err) {\n // err will be a SyntaxError\n}
\nSyntaxError
instances are unrecoverable in the context that created them –\nthey may only be caught by other contexts.\n\n
A subclass of Error
that indicates that a provided argument is not an\nallowable type. For example, passing a function to a parameter which expects a\nstring would be considered a TypeError.\n\n
require('url').parse(() => { });\n // throws TypeError, since it expected a string
\nNode.js will generate and throw TypeError
instances immediately as a form\nof argument validation.\n\n
These objects are available in all modules. Some of these objects aren't\nactually in the global scope but in the module scope - this will be noted.\n\n
\n", "globals": [ { "textRaw": "Class: Buffer", "type": "global", "name": "Buffer", "desc": "Used to handle binary data. See the [buffer section][].\n\n
\n" }, { "textRaw": "clearImmediate(immediateObject)", "type": "global", "name": "clearImmediate", "desc": "[clearImmediate
] is described in the [timers][] section.\n\n
[clearInterval
] is described in the [timers][] section.\n\n
[clearTimeout
] is described in the [timers][] section.\n\n
Used to print to stdout and stderr. See the [console
][] section.\n\n
In browsers, the top-level scope is the global scope. That means that in\nbrowsers if you're in the global scope var something
will define a global\nvariable. In Node.js this is different. The top-level scope is not the global\nscope; var something
inside an Node.js module will be local to that module.\n\n
The process object. See the [process
object][] section.\n\n
[setImmediate
] is described in the [timers][] section.\n\n
[setInterval
] is described in the [timers][] section.\n\n
[setTimeout
] is described in the [timers][] section.\n\n
The process
object is a global object and can be accessed from anywhere.\nIt is an instance of [EventEmitter
][].\n\n
This event is emitted when Node.js empties its event loop and has nothing else\nto schedule. Normally, Node.js exits when there is no work scheduled, but a\nlistener for 'beforeExit'
can make asynchronous calls, and cause Node.js to\ncontinue.\n\n
'beforeExit'
is not emitted for conditions causing explicit termination, such\nas [process.exit()
][] or uncaught exceptions, and should not be used as an\nalternative to the 'exit'
event unless the intention is to schedule more work.\n\n
If process is spawned with an IPC channel, 'disconnect'
will be emitted when\nIPC channel is closed. Read more in [child_process 'disconnect'
event][] doc.\n\n
Emitted when the process is about to exit. There is no way to prevent the\nexiting of the event loop at this point, and once all 'exit'
listeners have\nfinished running the process will exit. Therefore you must only perform\nsynchronous operations in this handler. This is a good hook to perform\nchecks on the module's state (like for unit tests). The callback takes one\nargument, the code the process is exiting with.\n\n
This event is only emitted when Node.js exits explicitly by process.exit() or\nimplicitly by the event loop draining.\n\n
\nExample of listening for 'exit'
:\n\n
process.on('exit', (code) => {\n // do *NOT* do this\n setTimeout(() => {\n console.log('This will not run');\n }, 0);\n console.log('About to exit with code:', code);\n});
\n",
"params": []
},
{
"textRaw": "Event: 'message'",
"type": "event",
"name": "message",
"params": [],
"desc": "Messages sent by [ChildProcess.send()
][] are obtained using the 'message'
\nevent on the child's process object.\n\n
Emitted whenever a Promise was rejected and an error handler was attached to it\n(for example with [promise.catch()
][]) later than after an event loop turn. This event\nis emitted with the following arguments:\n\n
p
the promise that was previously emitted in an 'unhandledRejection'
\nevent, but which has now gained a rejection handler.There is no notion of a top level for a promise chain at which rejections can\nalways be handled. Being inherently asynchronous in nature, a promise rejection\ncan be handled at a future point in time — possibly much later than the\nevent loop turn it takes for the 'unhandledRejection'
event to be emitted.\n\n
Another way of stating this is that, unlike in synchronous code where there is\nan ever-growing list of unhandled exceptions, with promises there is a\ngrowing-and-shrinking list of unhandled rejections. In synchronous code, the\n'uncaughtException'
event tells you when the list of unhandled exceptions\ngrows. And in asynchronous code, the 'unhandledRejection'
event tells you\nwhen the list of unhandled rejections grows, while the 'rejectionHandled'
\nevent tells you when the list of unhandled rejections shrinks.\n\n
For example using the rejection detection hooks in order to keep a map of all\nthe rejected promise reasons at a given time:\n\n
\nconst unhandledRejections = new Map();\nprocess.on('unhandledRejection', (reason, p) => {\n unhandledRejections.set(p, reason);\n});\nprocess.on('rejectionHandled', (p) => {\n unhandledRejections.delete(p);\n});
\nThis map will grow and shrink over time, reflecting rejections that start\nunhandled and then become handled. You could record the errors in some error\nlog, either periodically (probably best for long-running programs, allowing\nyou to clear the map, which in the case of a very buggy program could grow\nindefinitely) or upon process exit (more convenient for scripts).\n\n
\n", "params": [] }, { "textRaw": "Event: 'uncaughtException'", "type": "event", "name": "uncaughtException", "desc": "The 'uncaughtException'
event is emitted when an exception bubbles all the\nway back to the event loop. By default, Node.js handles such exceptions by\nprinting the stack trace to stderr and exiting. Adding a handler for the\n'uncaughtException'
event overrides this default behavior.\n\n
For example:\n\n
\nprocess.on('uncaughtException', (err) => {\n console.log(`Caught exception: ${err}`);\n});\n\nsetTimeout(() => {\n console.log('This will still run.');\n}, 500);\n\n// Intentionally cause an exception, but don't catch it.\nnonexistentFunc();\nconsole.log('This will not run.');
\n",
"modules": [
{
"textRaw": "Warning: Using `'uncaughtException'` correctly",
"name": "warning:_using_`'uncaughtexception'`_correctly",
"desc": "Note that 'uncaughtException'
is a crude mechanism for exception handling\nintended to be used only as a last resort. The event should not be used as\nan equivalent to On Error Resume Next
. Unhandled exceptions inherently mean\nthat an application is in an undefined state. Attempting to resume application\ncode without properly recovering from the exception can cause additional\nunforeseen and unpredictable issues.\n\n
Exceptions thrown from within the event handler will not be caught. Instead the\nprocess will exit with a non zero exit code and the stack trace will be printed.\nThis is to avoid infinite recursion.\n\n
\nAttempting to resume normally after an uncaught exception can be similar to\npulling out of the power cord when upgrading a computer -- nine out of ten\ntimes nothing happens - but the 10th time, the system becomes corrupted.\n\n
\nThe correct use of 'uncaughtException'
is to perform synchronous cleanup\nof allocated resources (e.g. file descriptors, handles, etc) before shutting\ndown the process. It is not safe to resume normal operation after\n'uncaughtException'
.\n\n
Emitted whenever a Promise
is rejected and no error handler is attached to\nthe promise within a turn of the event loop. When programming with promises\nexceptions are encapsulated as rejected promises. Such promises can be caught\nand handled using [promise.catch()
][] and rejections are propagated through\na promise chain. This event is useful for detecting and keeping track of\npromises that were rejected whose rejections were not handled yet. This event\nis emitted with the following arguments:\n\n
reason
the object with which the promise was rejected (usually an\n[Error
][] instance).p
the promise that was rejected.Here is an example that logs every unhandled rejection to the console\n\n
\nprocess.on('unhandledRejection', (reason, p) => {\n console.log("Unhandled Rejection at: Promise ", p, " reason: ", reason);\n // application specific logging, throwing an error, or other logic here\n});
\nFor example, here is a rejection that will trigger the 'unhandledRejection'
\nevent:\n\n
somePromise.then((res) => {\n return reportToUser(JSON.pasre(res)); // note the typo (`pasre`)\n}); // no `.catch` or `.then`
\nHere is an example of a coding pattern that will also trigger\n'unhandledRejection'
:\n\n
function SomeResource() {\n // Initially set the loaded status to a rejected promise\n this.loaded = Promise.reject(new Error('Resource not yet loaded!'));\n}\n\nvar resource = new SomeResource();\n// no .catch or .then on resource.loaded for at least a turn
\nIn cases like this, you may not want to track the rejection as a developer\nerror like you would for other 'unhandledRejection'
events. To address\nthis, you can either attach a dummy [.catch(() => { })
][promise.catch()
] handler to\nresource.loaded
, preventing the 'unhandledRejection'
event from being\nemitted, or you can use the ['rejectionHandled'
][] event.\n\n
Emitted whenever Node.js emits a process warning.\n\n
\nA process warning is similar to an error in that it describes exceptional\nconditions that are being brought to the user's attention. However, warnings\nare not part of the normal Node.js and JavaScript error handling flow.\nNode.js can emit warnings whenever it detects bad coding practices that could\nlead to sub-optimal application performance, bugs or security vulnerabilities.\n\n
\nThe event handler for 'warning'
events is called with a single warning
\nargument whose value is an Error
object. There are three key properties that\ndescribe the warning:\n\n
name
- The name of the warning (currently Warning
by default).message
- A system-provided description of the warning.stack
- A stack trace to the location in the code where the warning was\nissued.process.on('warning', (warning) => {\n console.warn(warning.name); // Print the warning name\n console.warn(warning.message); // Print the warning message\n console.warn(warning.stack); // Print the stack trace\n});
\nBy default, Node.js will print process warnings to stderr
. The --no-warnings
\ncommand-line option can be used to suppress the default console output but the\n'warning'
event will still be emitted by the process
object.\n\n
The following example illustrates the warning that is printed to stderr
when\ntoo many listeners have been added to an event\n\n
$ node\n> event.defaultMaxListeners = 1;\n> process.on('foo', () => {});\n> process.on('foo', () => {});\n> (node:38638) Warning: Possible EventEmitter memory leak detected. 2 foo\n... listeners added. Use emitter.setMaxListeners() to increase limit
\nIn contrast, the following example turns off the default warning output and\nadds a custom handler to the 'warning'
event:\n\n
$ node --no-warnings\n> var p = process.on('warning', (warning) => console.warn('Do not do that!'));\n> event.defaultMaxListeners = 1;\n> process.on('foo', () => {});\n> process.on('foo', () => {});\n> Do not do that!
\nThe --trace-warnings
command-line option can be used to have the default\nconsole output for warnings include the full stack trace of the warning.\n\n
The [process.emitWarning()
][process_emit_warning] method can be used to issue\ncustom or application specific warnings.\n\n
// Emit a warning using a string...\nprocess.emitWarning('Something happened!');\n // Prints: (node 12345) Warning: Something happened!\n\n// Emit a warning using an object...\nprocess.emitWarning('Something Happened!', 'CustomWarning');\n // Prints: (node 12345) CustomWarning: Something happened!\n\n// Emit a warning using a custom Error object...\nclass CustomWarning extends Error {\n constructor(message) {\n super(message);\n this.name = 'CustomWarning';\n Error.captureStackTrace(this, CustomWarning);\n }\n}\nconst myWarning = new CustomWarning('Something happened!');\nprocess.emitWarning(myWarning);\n // Prints: (node 12345) CustomWarning: Something happened!
\n",
"type": "module",
"displayName": "Emitting custom warnings"
},
{
"textRaw": "Emitting custom deprecation warnings",
"name": "emitting_custom_deprecation_warnings",
"desc": "Custom deprecation warnings can be emitted by setting the name
of a custom\nwarning to DeprecationWarning
. For instance:\n\n
process.emitWarning('This API is deprecated', 'DeprecationWarning');
\nOr,\n\n
\nconst err = new Error('This API is deprecated');\nerr.name = 'DeprecationWarning';\nprocess.emitWarning(err);
\nLaunching Node.js using the --throw-deprecation
command line flag will\ncause custom deprecation warnings to be thrown as exceptions.\n\n
Using the --trace-deprecation
command line flag will cause the custom\ndeprecation to be printed to stderr
along with the stack trace.\n\n
Using the --no-deprecation
command line flag will suppress all reporting\nof the custom deprecation.\n\n
The *-deprecation
command line flags only affect warnings that use the name\nDeprecationWarning
.\n\n
Emitted when the processes receives a signal. See sigaction(2) for a list of\nstandard POSIX signal names such as SIGINT
, SIGHUP
, etc.\n\n
Example of listening for SIGINT
:\n\n
// Start reading from stdin so we don't exit.\nprocess.stdin.resume();\n\nprocess.on('SIGINT', () => {\n console.log('Got SIGINT. Press Control-D to exit.');\n});
\nAn easy way to send the SIGINT
signal is with Control-C
in most terminal\nprograms.\n\n
Note:\n\n
\nSIGUSR1
is reserved by Node.js to start the debugger. It's possible to\ninstall a listener but that won't stop the debugger from starting.SIGTERM
and SIGINT
have default handlers on non-Windows platforms that\nresets the terminal mode before exiting with code 128 + signal number
. If\none of these signals has a listener installed, its default behavior will be\nremoved (Node.js will no longer exit).SIGPIPE
is ignored by default. It can have a listener installed.SIGHUP
is generated on Windows when the console window is closed, and on other\nplatforms under various similar conditions, see signal(7). It can have a\nlistener installed, however Node.js will be unconditionally terminated by\nWindows about 10 seconds later. On non-Windows platforms, the default\nbehavior of SIGHUP
is to terminate Node.js, but once a listener has been\ninstalled its default behavior will be removed.SIGTERM
is not supported on Windows, it can be listened on.SIGINT
from the terminal is supported on all platforms, and can usually be\ngenerated with CTRL+C
(though this may be configurable). It is not generated\nwhen terminal raw mode is enabled.SIGBREAK
is delivered on Windows when CTRL+BREAK
is pressed, on\nnon-Windows\nplatforms it can be listened on, but there is no way to send or generate it.SIGWINCH
is delivered when the console has been resized. On Windows, this\nwill only happen on write to the console when the cursor is being moved, or\nwhen a readable tty is used in raw mode.SIGKILL
cannot have a listener installed, it will unconditionally terminate\nNode.js on all platforms.SIGSTOP
cannot have a listener installed.Note that Windows does not support sending Signals, but Node.js offers some\nemulation with [process.kill()
][], and [ChildProcess.kill()
][]. Sending signal 0
\ncan be used to test for the existence of a process. Sending SIGINT
,\nSIGTERM
, and SIGKILL
cause the unconditional termination of the target\nprocess.\n\n
Node.js will normally exit with a 0
status code when no more async\noperations are pending. The following status codes are used in other\ncases:\n\n
1
Uncaught Fatal Exception - There was an uncaught exception,\nand it was not handled by a domain or an ['uncaughtException'
][] event\nhandler.2
- Unused (reserved by Bash for builtin misuse)3
Internal JavaScript Parse Error - The JavaScript source code\ninternal in Node.js's bootstrapping process caused a parse error. This\nis extremely rare, and generally can only happen during development\nof Node.js itself.4
Internal JavaScript Evaluation Failure - The JavaScript\nsource code internal in Node.js's bootstrapping process failed to\nreturn a function value when evaluated. This is extremely rare, and\ngenerally can only happen during development of Node.js itself.5
Fatal Error - There was a fatal unrecoverable error in V8.\nTypically a message will be printed to stderr with the prefix FATAL\nERROR
.6
Non-function Internal Exception Handler - There was an\nuncaught exception, but the internal fatal exception handler\nfunction was somehow set to a non-function, and could not be called.7
Internal Exception Handler Run-Time Failure - There was an\nuncaught exception, and the internal fatal exception handler\nfunction itself threw an error while attempting to handle it. This\ncan happen, for example, if a ['uncaughtException'
][] or\ndomain.on('error')
handler throws an error.8
- Unused. In previous versions of Node.js, exit code 8 sometimes\nindicated an uncaught exception.9
- Invalid Argument - Either an unknown option was specified,\nor an option requiring a value was provided without a value.10
Internal JavaScript Run-Time Failure - The JavaScript\nsource code internal in Node.js's bootstrapping process threw an error\nwhen the bootstrapping function was called. This is extremely rare,\nand generally can only happen during development of Node.js itself.12
Invalid Debug Argument - The --debug
and/or --debug-brk
\noptions were set, but an invalid port number was chosen.>128
Signal Exits - If Node.js receives a fatal signal such as\nSIGKILL
or SIGHUP
, then its exit code will be 128
plus the\nvalue of the signal code. This is a standard Unix practice, since\nexit codes are defined to be 7-bit integers, and signal exits set\nthe high-order bit, and then contain the value of the signal code.This causes Node.js to emit an abort. This will cause Node.js to exit and\ngenerate a core file.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "process.chdir(directory)", "type": "method", "name": "chdir", "desc": "Changes the current working directory of the process or throws an exception if that fails.\n\n
\nconsole.log(`Starting directory: ${process.cwd()}`);\ntry {\n process.chdir('/tmp');\n console.log(`New directory: ${process.cwd()}`);\n}\ncatch (err) {\n console.log(`chdir: ${err}`);\n}
\n",
"signatures": [
{
"params": [
{
"name": "directory"
}
]
}
]
},
{
"textRaw": "process.cpuUsage([previousValue])",
"type": "method",
"name": "cpuUsage",
"desc": "Returns the user and system CPU time usage of the current process, in an object\nwith properties user
and system
, whose values are microsecond values\n(millionth of a second). These values measure time spent in user and\nsystem code respectively, and may end up being greater than actual elapsed time\nif multiple CPU cores are performing work for this process.\n\n
The result of a previous call to process.cpuUsage()
can be passed as the\nargument to the function, to get a diff reading.\n\n
const startUsage = process.cpuUsage();\n// { user: 38579, system: 6986 }\n\n// spin the CPU for 500 milliseconds\nconst now = Date.now();\nwhile (Date.now() - now < 500);\n\nconsole.log(process.cpuUsage(startUsage));\n// { user: 514883, system: 11226 }
\n",
"signatures": [
{
"params": [
{
"name": "previousValue",
"optional": true
}
]
}
]
},
{
"textRaw": "process.cwd()",
"type": "method",
"name": "cwd",
"desc": "Returns the current working directory of the process.\n\n
\nconsole.log(`Current directory: ${process.cwd()}`);
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.disconnect()",
"type": "method",
"name": "disconnect",
"desc": "Close the IPC channel to the parent process, allowing this child to exit\ngracefully once there are no other connections keeping it alive.\n\n
\nIdentical to the parent process's [ChildProcess.disconnect()
][].\n\n
If Node.js was not spawned with an IPC channel, process.disconnect()
will be\nundefined.\n\n
The process.emitWarning()
method can be used to emit custom or application\nspecific process warnings. These can be listened for by adding a handler to the\n[process.on('warning')
][process_warning] event.\n\n
// Emit a warning using a string...\nprocess.emitWarning('Something happened!');\n // Emits: (node: 56338) Warning: Something happened!
\n// Emit a warning using a string and a name...\nprocess.emitWarning('Something Happened!', 'CustomWarning');\n // Emits: (node:56338) CustomWarning: Something Happened!
\nIn each of the previous examples, an Error
object is generated internally by\nprocess.emitWarning()
and passed through to the\n[process.on('warning')
][process_warning] event.\n\n
process.on('warning', (warning) => {\n console.warn(warning.name);\n console.warn(warning.message);\n console.warn(warning.stack);\n});
\nIf warning
is passed as an Error
object, it will be passed through to the\nprocess.on('warning')
event handler unmodified (and the optional name
\nand ctor
arguments will be ignored):\n\n
// Emit a warning using an Error object...\nconst myWarning = new Error('Warning! Something happened!');\nmyWarning.name = 'CustomWarning';\n\nprocess.emitWarning(myWarning);\n // Emits: (node:56338) CustomWarning: Warning! Something Happened!
\nA TypeError
is thrown if warning
is anything other than a string or Error
\nobject.\n\n
Note that while process warnings use Error
objects, the process warning\nmechanism is not a replacement for normal error handling mechanisms.\n\n
The following additional handling is implemented if the warning name
is\nDeprecationWarning
:\n\n
--throw-deprecation
command-line flag is used, the deprecation\nwarning is thrown as an exception rather than being emitted as an event.--no-deprecation
command-line flag is used, the deprecation\nwarning is suppressed.--trace-deprecation
command-line flag is used, the deprecation\nwarning is printed to stderr
along with the full stack trace.As a best practice, warnings should be emitted only once per process. To do\nso, it is recommended to place the emitWarning()
behind a simple boolean\nflag as illustrated in the example below:\n\n
var warned = false;\nfunction emitMyWarning() {\n if (!warned) {\n process.emitWarning('Only warn once!');\n warned = true;\n }\n}\nemitMyWarning();\n // Emits: (node: 56339) Warning: Only warn once!\nemitMyWarning();\n // Emits nothing
\n",
"type": "module",
"displayName": "Avoiding duplicate warnings"
}
]
},
{
"textRaw": "process.exit([code])",
"type": "method",
"name": "exit",
"signatures": [
{
"params": [
{
"textRaw": "`code` {Integer} The exit code. Defaults to `0`. ",
"name": "code",
"type": "Integer",
"desc": "The exit code. Defaults to `0`.",
"optional": true
}
]
},
{
"params": [
{
"name": "code",
"optional": true
}
]
}
],
"desc": "The process.exit()
method instructs Node.js to terminate the process as\nquickly as possible with the specified exit code
. If the code
is omitted, \nexit uses either the 'success' code 0
or the value of process.exitCode
if\nspecified.\n\n
To exit with a 'failure' code:\n\n
\nprocess.exit(1);
\nThe shell that executed Node.js should see the exit code as 1
.\n\n
It is important to note that calling process.exit()
will force the process to\nexit as quickly as possible even if there are still asynchronous operations \npending that have not yet completed fully, including I/O operations to\nprocess.stdout
and process.stderr
.\n\n
In most situations, it is not actually necessary to call process.exit()
\nexplicitly. The Node.js process will exit on it's own if there is no additional\nwork pending in the event loop. The process.exitCode
property can be set to\ntell the process which exit code to use when the process exits gracefully.\n\n
For instance, the following example illustrates a misuse of the \nprocess.exit()
method that could lead to data printed to stdout being \ntruncated and lost:\n\n
// This is an example of what *not* to do:\nif (someConditionNotMet()) {\n printUsageToStdout();\n process.exit(1);\n}
\nThe reason this is problematic is because writes to process.stdout
in Node.js\nare non-blocking and may occur over multiple ticks of the Node.js event loop.\nCalling process.exit()
, however, forces the process to exit before those\nadditional writes to stdout
can be performed.\n\n
Rather than calling process.exit()
directly, the code should set the\nprocess.exitCode
and allow the process to exit naturally by avoiding\nscheduling any additional work for the event loop:\n\n
// How to properly set the exit code while letting\n// the process exit gracefully.\nif (someConditionNotMet()) {\n printUsageToStdout();\n process.exitCode = 1;\n}
\nIf it is necessary to terminate the Node.js process due to an error condition,\nthrowing an uncaught error and allowing the process to terminate accordingly\nis safer than calling process.exit()
.\n\n
Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nGets the effective group identity of the process. (See getegid(2).)\nThis is the numerical group id, not the group name.\n\n
\nif (process.getegid) {\n console.log(`Current gid: ${process.getegid()}`);\n}
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.geteuid()",
"type": "method",
"name": "geteuid",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nGets the effective user identity of the process. (See geteuid(2).)\nThis is the numerical userid, not the username.\n\n
\nif (process.geteuid) {\n console.log(`Current uid: ${process.geteuid()}`);\n}
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.getgid()",
"type": "method",
"name": "getgid",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nGets the group identity of the process. (See getgid(2).)\nThis is the numerical group id, not the group name.\n\n
\nif (process.getgid) {\n console.log(`Current gid: ${process.getgid()}`);\n}
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.getgroups()",
"type": "method",
"name": "getgroups",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nReturns an array with the supplementary group IDs. POSIX leaves it unspecified\nif the effective group ID is included but Node.js ensures it always is.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "process.getuid()", "type": "method", "name": "getuid", "desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nGets the user identity of the process. (See getuid(2).)\nThis is the numerical userid, not the username.\n\n
\nif (process.getuid) {\n console.log(`Current uid: ${process.getuid()}`);\n}
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.hrtime()",
"type": "method",
"name": "hrtime",
"desc": "Returns the current high-resolution real time in a [seconds, nanoseconds]
\ntuple Array. It is relative to an arbitrary time in the past. It is not\nrelated to the time of day and therefore not subject to clock drift. The\nprimary use is for measuring performance between intervals.\n\n
You may pass in the result of a previous call to process.hrtime()
to get\na diff reading, useful for benchmarks and measuring intervals:\n\n
var time = process.hrtime();\n// [ 1800216, 25 ]\n\nsetTimeout(() => {\n var diff = process.hrtime(time);\n // [ 1, 552 ]\n\n console.log('benchmark took %d nanoseconds', diff[0] * 1e9 + diff[1]);\n // benchmark took 1000000527 nanoseconds\n}, 1000);
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.initgroups(user, extra_group)",
"type": "method",
"name": "initgroups",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nReads /etc/group and initializes the group access list, using all groups of\nwhich the user is a member. This is a privileged operation, meaning you need\nto be root or have the CAP_SETGID
capability.\n\n
user
is a user name or user ID. extra_group
is a group name or group ID.\n\n
Some care needs to be taken when dropping privileges. Example:\n\n
\nconsole.log(process.getgroups()); // [ 0 ]\nprocess.initgroups('bnoordhuis', 1000); // switch user\nconsole.log(process.getgroups()); // [ 27, 30, 46, 1000, 0 ]\nprocess.setgid(1000); // drop root gid\nconsole.log(process.getgroups()); // [ 27, 30, 46, 1000 ]
\n",
"signatures": [
{
"params": [
{
"name": "user"
},
{
"name": "extra_group"
}
]
}
]
},
{
"textRaw": "process.kill(pid[, signal])",
"type": "method",
"name": "kill",
"desc": "Send a signal to a process. pid
is the process id and signal
is the\nstring describing the signal to send. Signal names are strings like\n'SIGINT'
or 'SIGHUP'
. If omitted, the signal will be 'SIGTERM'
.\nSee [Signal Events][] and kill(2) for more information.\n\n
Will throw an error if target does not exist, and as a special case, a signal\nof 0
can be used to test for the existence of a process. Windows platforms\nwill throw an error if the pid
is used to kill a process group.\n\n
Note that even though the name of this function is process.kill
, it is really\njust a signal sender, like the kill
system call. The signal sent may do\nsomething other than kill the target process.\n\n
Example of sending a signal to yourself:\n\n
\nprocess.on('SIGHUP', () => {\n console.log('Got SIGHUP signal.');\n});\n\nsetTimeout(() => {\n console.log('Exiting.');\n process.exit(0);\n}, 100);\n\nprocess.kill(process.pid, 'SIGHUP');
\nNote: When SIGUSR1 is received by Node.js it starts the debugger, see\n[Signal Events][].\n\n
\n", "signatures": [ { "params": [ { "name": "pid" }, { "name": "signal", "optional": true } ] } ] }, { "textRaw": "process.memoryUsage()", "type": "method", "name": "memoryUsage", "desc": "Returns an object describing the memory usage of the Node.js process\nmeasured in bytes.\n\n
\nconst util = require('util');\n\nconsole.log(util.inspect(process.memoryUsage()));
\nThis will generate:\n\n
\n{ rss: 4935680,\n heapTotal: 1826816,\n heapUsed: 650472 }
\nheapTotal
and heapUsed
refer to V8's memory usage.\n\n\n
Once the current event loop turn runs to completion, call the callback\nfunction.\n\n
\nThis is not a simple alias to [setTimeout(fn, 0)
][], it's much more\nefficient. It runs before any additional I/O events (including\ntimers) fire in subsequent ticks of the event loop.\n\n
console.log('start');\nprocess.nextTick(() => {\n console.log('nextTick callback');\n});\nconsole.log('scheduled');\n// Output:\n// start\n// scheduled\n// nextTick callback
\nThis is important in developing APIs where you want to give the user the\nchance to assign event handlers after an object has been constructed,\nbut before any I/O has occurred.\n\n
\nfunction MyThing(options) {\n this.setupOptions(options);\n\n process.nextTick(() => {\n this.startDoingStuff();\n });\n}\n\nvar thing = new MyThing();\nthing.getReadyForStuff();\n\n// thing.startDoingStuff() gets called now, not before.
\nIt is very important for APIs to be either 100% synchronous or 100%\nasynchronous. Consider this example:\n\n
\n// WARNING! DO NOT USE! BAD UNSAFE HAZARD!\nfunction maybeSync(arg, cb) {\n if (arg) {\n cb();\n return;\n }\n\n fs.stat('file', cb);\n}
\nThis API is hazardous. If you do this:\n\n
\nmaybeSync(true, () => {\n foo();\n});\nbar();
\nthen it's not clear whether foo()
or bar()
will be called first.\n\n
This approach is much better:\n\n
\nfunction definitelyAsync(arg, cb) {\n if (arg) {\n process.nextTick(cb);\n return;\n }\n\n fs.stat('file', cb);\n}
\nNote: the nextTick queue is completely drained on each pass of the\nevent loop before additional I/O is processed. As a result,\nrecursively setting nextTick callbacks will block any I/O from\nhappening, just like a while(true);
loop.\n\n
When Node.js is spawned with an IPC channel attached, it can send messages to its\nparent process using process.send()
. Each will be received as a\n['message'
][] event on the parent's [ChildProcess
][] object.\n\n
Note: this function uses [JSON.stringify()
][] internally to serialize the message
.\n\n
If Node.js was not spawned with an IPC channel, process.send()
will be undefined.\n\n
Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nSets the effective group identity of the process. (See setegid(2).)\nThis accepts either a numerical ID or a group name string. If a group name\nis specified, this method blocks while resolving it to a numerical ID.\n\n
\nif (process.getegid && process.setegid) {\n console.log(`Current gid: ${process.getegid()}`);\n try {\n process.setegid(501);\n console.log(`New gid: ${process.getegid()}`);\n }\n catch (err) {\n console.log(`Failed to set gid: ${err}`);\n }\n}
\n",
"signatures": [
{
"params": [
{
"name": "id"
}
]
}
]
},
{
"textRaw": "process.seteuid(id)",
"type": "method",
"name": "seteuid",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nSets the effective user identity of the process. (See seteuid(2).)\nThis accepts either a numerical ID or a username string. If a username\nis specified, this method blocks while resolving it to a numerical ID.\n\n
\nif (process.geteuid && process.seteuid) {\n console.log(`Current uid: ${process.geteuid()}`);\n try {\n process.seteuid(501);\n console.log(`New uid: ${process.geteuid()}`);\n }\n catch (err) {\n console.log(`Failed to set uid: ${err}`);\n }\n}
\n",
"signatures": [
{
"params": [
{
"name": "id"
}
]
}
]
},
{
"textRaw": "process.setgid(id)",
"type": "method",
"name": "setgid",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nSets the group identity of the process. (See setgid(2).) This accepts either\na numerical ID or a group name string. If a group name is specified, this method\nblocks while resolving it to a numerical ID.\n\n
\nif (process.getgid && process.setgid) {\n console.log(`Current gid: ${process.getgid()}`);\n try {\n process.setgid(501);\n console.log(`New gid: ${process.getgid()}`);\n }\n catch (err) {\n console.log(`Failed to set gid: ${err}`);\n }\n}
\n",
"signatures": [
{
"params": [
{
"name": "id"
}
]
}
]
},
{
"textRaw": "process.setgroups(groups)",
"type": "method",
"name": "setgroups",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nSets the supplementary group IDs. This is a privileged operation, meaning you\nneed to be root or have the CAP_SETGID
capability.\n\n
The list can contain group IDs, group names or both.\n\n
\n", "signatures": [ { "params": [ { "name": "groups" } ] } ] }, { "textRaw": "process.setuid(id)", "type": "method", "name": "setuid", "desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nSets the user identity of the process. (See setuid(2).) This accepts either\na numerical ID or a username string. If a username is specified, this method\nblocks while resolving it to a numerical ID.\n\n
\nif (process.getuid && process.setuid) {\n console.log(`Current uid: ${process.getuid()}`);\n try {\n process.setuid(501);\n console.log(`New uid: ${process.getuid()}`);\n }\n catch (err) {\n console.log(`Failed to set uid: ${err}`);\n }\n}
\n",
"signatures": [
{
"params": [
{
"name": "id"
}
]
}
]
},
{
"textRaw": "process.umask([mask])",
"type": "method",
"name": "umask",
"desc": "Sets or reads the process's file mode creation mask. Child processes inherit\nthe mask from the parent process. Returns the old mask if mask
argument is\ngiven, otherwise returns the current mask.\n\n
const newmask = 0o022;\nconst oldmask = process.umask(newmask);\nconsole.log(\n `Changed umask from ${oldmask.toString(8)} to ${newmask.toString(8)}`\n);
\n",
"signatures": [
{
"params": [
{
"name": "mask",
"optional": true
}
]
}
]
},
{
"textRaw": "process.uptime()",
"type": "method",
"name": "uptime",
"desc": "Number of seconds Node.js has been running.\n\n
\n", "signatures": [ { "params": [] } ] } ], "properties": [ { "textRaw": "process.arch", "name": "arch", "desc": "What processor architecture you're running on: 'arm'
, 'ia32'
, or 'x64'
.\n\n
console.log('This processor architecture is ' + process.arch);
\n"
},
{
"textRaw": "process.argv",
"name": "argv",
"desc": "An array containing the command line arguments. The first element will be\n'node', the second element will be the name of the JavaScript file. The\nnext elements will be any additional command line arguments.\n\n
\n// print process.argv\nprocess.argv.forEach((val, index, array) => {\n console.log(`${index}: ${val}`);\n});
\nThis will generate:\n\n
\n$ node process-2.js one two=three four\n0: node\n1: /Users/mjr/work/node/process-2.js\n2: one\n3: two=three\n4: four
\n"
},
{
"textRaw": "process.config",
"name": "config",
"desc": "An Object containing the JavaScript representation of the configure options\nthat were used to compile the current Node.js executable. This is the same as\nthe config.gypi
file that was produced when running the ./configure
script.\n\n
An example of the possible output looks like:\n\n
\n{\n target_defaults:\n { cflags: [],\n default_configuration: 'Release',\n defines: [],\n include_dirs: [],\n libraries: [] },\n variables:\n {\n host_arch: 'x64',\n node_install_npm: 'true',\n node_prefix: '',\n node_shared_cares: 'false',\n node_shared_http_parser: 'false',\n node_shared_libuv: 'false',\n node_shared_zlib: 'false',\n node_use_dtrace: 'false',\n node_use_openssl: 'true',\n node_shared_openssl: 'false',\n strict_aliasing: 'true',\n target_arch: 'x64',\n v8_use_snapshot: 'true'\n }\n}
\nNote: the process.config
property is not read-only and there are existing\nmodules in the ecosystem that are known to extend, modify, or entirely replace\nthe value of process.config
.\n\n
If process.connected
is false
, it is no longer possible to send messages.\n\n
An object containing the user environment. See environ(7).\n\n
\nAn example of this object looks like:\n\n
\n{ TERM: 'xterm-256color',\n SHELL: '/usr/local/bin/bash',\n USER: 'maciej',\n PATH: '~/.bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin',\n PWD: '/Users/maciej',\n EDITOR: 'vim',\n SHLVL: '1',\n HOME: '/Users/maciej',\n LOGNAME: 'maciej',\n _: '/usr/local/bin/node' }
\nYou can write to this object, but changes won't be reflected outside of your\nprocess. That means that the following won't work:\n\n
\n$ node -e 'process.env.foo = "bar"' && echo $foo
\nBut this will:\n\n
\nprocess.env.foo = 'bar';\nconsole.log(process.env.foo);
\nAssigning a property on process.env
will implicitly convert the value\nto a string.\n\n
Example:\n\n
\nprocess.env.test = null;\nconsole.log(process.env.test);\n// => 'null'\nprocess.env.test = undefined;\nconsole.log(process.env.test);\n// => 'undefined'
\nUse delete
to delete a property from process.env
.\n\n
Example:\n\n
\nprocess.env.TEST = 1;\ndelete process.env.TEST;\nconsole.log(process.env.TEST);\n// => undefined
\n"
},
{
"textRaw": "process.execArgv",
"name": "execArgv",
"desc": "This is the set of Node.js-specific command line options from the\nexecutable that started the process. These options do not show up in\n[process.argv
][], and do not include the Node.js executable, the name of\nthe script, or any options following the script name. These options\nare useful in order to spawn child processes with the same execution\nenvironment as the parent.\n\n
Example:\n\n
\n$ node --harmony script.js --version
\nresults in process.execArgv:\n\n
\n['--harmony']
\nand process.argv:\n\n
\n['/usr/local/bin/node', 'script.js', '--version']
\n"
},
{
"textRaw": "process.execPath",
"name": "execPath",
"desc": "This is the absolute pathname of the executable that started the process.\n\n
\nExample:\n\n
\n/usr/local/bin/node
\n"
},
{
"textRaw": "process.exitCode",
"name": "exitCode",
"desc": "A number which will be the process exit code, when the process either\nexits gracefully, or is exited via [process.exit()
][] without specifying\na code.\n\n
Specifying a code to [process.exit(code)
][process.exit()
] will override any \nprevious setting of process.exitCode
.\n\n\n
Alternate way to retrieve [require.main
][]. The difference is that if the main\nmodule changes at runtime, [require.main
][] might still refer to the original main\nmodule in modules that were required before the change occurred. Generally it's\nsafe to assume that the two refer to the same module.\n\n
As with [require.main
][], it will be undefined
if there was no entry script.\n\n
The PID of the process.\n\n
\nconsole.log(`This process is pid ${process.pid}`);
\n"
},
{
"textRaw": "process.platform",
"name": "platform",
"desc": "What platform you're running on:\n'darwin'
, 'freebsd'
, 'linux'
, 'sunos'
or 'win32'
\n\n
console.log(`This platform is ${process.platform}`);
\n"
},
{
"textRaw": "process.release",
"name": "release",
"desc": "An Object containing metadata related to the current release, including URLs\nfor the source tarball and headers-only tarball.\n\n
\nprocess.release
contains the following properties:\n\n
name
: a string with a value that will always be 'node'
for Node.js. For\nlegacy io.js releases, this will be 'io.js'
.sourceUrl
: a complete URL pointing to a .tar.gz file containing the\nsource of the current release.headersUrl
: a complete URL pointing to a .tar.gz file containing only\nthe header files for the current release. This file is significantly smaller\nthan the full source file and can be used for compiling add-ons against\nNode.js.libUrl
: a complete URL pointing to an node.lib file matching the\narchitecture and version of the current release. This file is used for\ncompiling add-ons against Node.js. This property is only present on Windows\nbuilds of Node.js and will be missing on all other platforms.e.g.\n\n
\n{ name: 'node',\n sourceUrl: 'https://nodejs.org/download/release/v4.0.0/node-v4.0.0.tar.gz',\n headersUrl: 'https://nodejs.org/download/release/v4.0.0/node-v4.0.0-headers.tar.gz',\n libUrl: 'https://nodejs.org/download/release/v4.0.0/win-x64/node.lib' }
\nIn custom builds from non-release versions of the source tree, only the\nname
property may be present. The additional properties should not be\nrelied upon to exist.\n\n
A writable stream to stderr (on fd 2
).\n\n
process.stderr
and process.stdout
are unlike other streams in Node.js in\nthat they cannot be closed ([end()
][] will throw), they never emit the ['finish'
][]\nevent and that writes can block when output is redirected to a file (although\ndisks are fast and operating systems normally employ write-back caching so it\nshould be a very rare occurrence indeed.)\n\n
A Readable Stream
for stdin (on fd 0
).\n\n
Example of opening standard input and listening for both events:\n\n
\nprocess.stdin.setEncoding('utf8');\n\nprocess.stdin.on('readable', () => {\n var chunk = process.stdin.read();\n if (chunk !== null) {\n process.stdout.write(`data: ${chunk}`);\n }\n});\n\nprocess.stdin.on('end', () => {\n process.stdout.write('end');\n});
\nAs a Stream, process.stdin
can also be used in "old" mode that is compatible\nwith scripts written for node.js prior to v0.10.\nFor more information see [Stream compatibility][].\n\n
In "old" Streams mode the stdin stream is paused by default, so one\nmust call process.stdin.resume()
to read from it. Note also that calling\nprocess.stdin.resume()
itself would switch stream to "old" mode.\n\n
If you are starting a new project you should prefer a more recent "new" Streams\nmode over "old" one.\n\n
\n" }, { "textRaw": "process.stdout", "name": "stdout", "desc": "A Writable Stream
to stdout
(on fd 1
).\n\n
For example, a console.log
equivalent could look like this:\n\n
console.log = (msg) => {\n process.stdout.write(`${msg}\\n`);\n};
\nprocess.stderr
and process.stdout
are unlike other streams in Node.js in\nthat they cannot be closed ([end()
][] will throw), they never emit the ['finish'
][]\nevent and that writes can block when output is redirected to a file (although\ndisks are fast and operating systems normally employ write-back caching so it\nshould be a very rare occurrence indeed.)\n\n
To check if Node.js is being run in a TTY context, read the isTTY
property\non process.stderr
, process.stdout
, or process.stdin
:\n\n
$ node -p "Boolean(process.stdin.isTTY)"\ntrue\n$ echo "foo" | node -p "Boolean(process.stdin.isTTY)"\nfalse\n\n$ node -p "Boolean(process.stdout.isTTY)"\ntrue\n$ node -p "Boolean(process.stdout.isTTY)" | cat\nfalse
\nSee [the tty docs][] for more information.\n\n
\n" }, { "textRaw": "process.title", "name": "title", "desc": "Getter/setter to set what is displayed in ps
.\n\n
When used as a setter, the maximum length is platform-specific and probably\nshort.\n\n
\nOn Linux and OS X, it's limited to the size of the binary name plus the\nlength of the command line arguments because it overwrites the argv memory.\n\n
\nv0.8 allowed for longer process title strings by also overwriting the environ\nmemory but that was potentially insecure/confusing in some (rather obscure)\ncases.\n\n
\n" }, { "textRaw": "process.version", "name": "version", "desc": "A compiled-in property that exposes NODE_VERSION
.\n\n
console.log(`Version: ${process.version}`);
\n"
},
{
"textRaw": "process.versions",
"name": "versions",
"desc": "A property exposing version strings of Node.js and its dependencies.\n\n
\nconsole.log(process.versions);
\nWill print something like:\n\n
\n{ http_parser: '2.3.0',\n node: '1.1.1',\n v8: '4.1.0.14',\n uv: '1.3.0',\n zlib: '1.2.8',\n ares: '1.10.0-DEV',\n modules: '43',\n icu: '55.1',\n openssl: '1.0.1k' }
\n"
}
]
}
],
"vars": [
{
"textRaw": "\\_\\_dirname",
"name": "\\_\\_dirname",
"type": "var",
"desc": "The name of the directory that the currently executing script resides in.\n\n
\nExample: running node example.js
from /Users/mjr
\n\n
console.log(__dirname);\n// /Users/mjr
\n__dirname
isn't actually a global but rather local to each module.\n\n
For instance, given two modules: a
and b
, where b
is a dependency of\na
and there is a directory structure of:\n\n
/Users/mjr/app/a.js
/Users/mjr/app/node_modules/b/b.js
References to __dirname
within b.js
will return\n/Users/mjr/app/node_modules/b
while references to __dirname
within a.js
\nwill return /Users/mjr/app
.\n\n
The filename of the code being executed. This is the resolved absolute path\nof this code file. For a main program this is not necessarily the same\nfilename used in the command line. The value inside a module is the path\nto that module file.\n\n
\nExample: running node example.js
from /Users/mjr
\n\n
console.log(__filename);\n// /Users/mjr/example.js
\n__filename
isn't actually a global but rather local to each module.\n\n
A reference to the module.exports
that is shorter to type.\nSee [module system documentation][] for details on when to use exports
and\nwhen to use module.exports
.\n\n
exports
isn't actually a global but rather local to each module.\n\n
See the [module system documentation][] for more information.\n\n
\n" }, { "textRaw": "module", "name": "module", "type": "var", "desc": "A reference to the current module. In particular\nmodule.exports
is used for defining what a module exports and makes\navailable through require()
.\n\n
module
isn't actually a global but rather local to each module.\n\n
See the [module system documentation][] for more information.\n\n
\n" }, { "textRaw": "require()", "type": "var", "name": "require", "desc": "To require modules. See the [Modules][] section. require
isn't actually a\nglobal but rather local to each module.\n\n
Modules are cached in this object when they are required. By deleting a key\nvalue from this object, the next require
will reload the module. Note that\nthis does not apply to [native addons][], for which reloading will result in an\nError.\n\n
Instruct require
on how to handle certain file extensions.\n\n
Process files with the extension .sjs
as .js
:\n\n
require.extensions['.sjs'] = require.extensions['.js'];
\nDeprecated In the past, this list has been used to load\nnon-JavaScript modules into Node.js by compiling them on-demand.\nHowever, in practice, there are much better ways to do this, such as\nloading modules via some other Node.js program, or compiling them to\nJavaScript ahead of time.\n\n
\nSince the Module system is locked, this feature will probably never go\naway. However, it may have subtle bugs and complexities that are best\nleft untouched.\n\n
\n" } ], "methods": [ { "textRaw": "require.resolve()", "type": "method", "name": "resolve", "desc": "Use the internal require()
machinery to look up the location of a module,\nbut rather than loading the module, just return the resolved filename.\n\n
Node.js Addons are dynamically-linked shared objects, written in C or C++, that\ncan be loaded into Node.js using the [require()
][require] function, and used\njust as if they were an ordinary Node.js module. They are used primarily to\nprovide an interface between JavaScript running in Node.js and C/C++ libraries.\n\n
At the moment, the method for implementing Addons is rather complicated,\ninvolving knowledge of several components and APIs :\n\n
\nV8: the C++ library Node.js currently uses to provide the\nJavaScript implementation. V8 provides the mechanisms for creating objects,\ncalling functions, etc. V8's API is documented mostly in the\nv8.h
header file (deps/v8/include/v8.h
in the Node.js source\ntree), which is also available [online][v8-docs].
[libuv][]: The C library that implements the Node.js event loop, its worker\nthreads and all of the asynchronous behaviors of the platform. It also\nserves as a cross-platform abstraction library, giving easy, POSIX-like\naccess across all major operating systems to many common system tasks, such\nas interacting with the filesystem, sockets, timers and system events. libuv\nalso provides a pthreads-like threading abstraction that may be used to\npower more sophisticated asynchronous Addons that need to move beyond the\nstandard event loop. Addon authors are encouraged to think about how to\navoid blocking the event loop with I/O or other time-intensive tasks by\noff-loading work via libuv to non-blocking system operations, worker threads\nor a custom use of libuv's threads.
\nInternal Node.js libraries. Node.js itself exports a number of C/C++ APIs\nthat Addons can use — the most important of which is the\nnode::ObjectWrap
class.
Node.js includes a number of other statically linked libraries including\nOpenSSL. These other libraries are located in the deps/
directory in the\nNode.js source tree. Only the V8 and OpenSSL symbols are purposefully\nre-exported by Node.js and may be used to various extents by Addons.\nSee [Linking to Node.js' own dependencies][] for additional information.
All of the following examples are available for [download][] and may\nbe used as a starting-point for your own Addon.\n\n
\n", "modules": [ { "textRaw": "Hello world", "name": "hello_world", "desc": "This "Hello world" example is a simple Addon, written in C++, that is the\nequivalent of the following JavaScript code:\n\n
\nmodule.exports.hello = () => 'world';
\nFirst, create the file hello.cc
:\n\n
// hello.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid Method(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n args.GetReturnValue().Set(String::NewFromUtf8(isolate, "world"));\n}\n\nvoid init(Local<Object> exports) {\n NODE_SET_METHOD(exports, "hello", Method);\n}\n\nNODE_MODULE(addon, init)\n\n} // namespace demo
\nNote that all Node.js Addons must export an initialization function following\nthe pattern:\n\n
\nvoid Initialize(Local<Object> exports);\nNODE_MODULE(module_name, Initialize)
\nThere is no semi-colon after NODE_MODULE
as it's not a function (see\nnode.h
).\n\n
The module_name
must match the filename of the final binary (excluding\nthe .node suffix).\n\n
In the hello.cc
example, then, the initialization function is init
and the\nAddon module name is addon
.\n\n
Once the source code has been written, it must be compiled into the binary\naddon.node
file. To do so, create a file called binding.gyp
in the\ntop-level of the project describing the build configuration of your module\nusing a JSON-like format. This file is used by [node-gyp][] -- a tool written\nspecifically to compile Node.js Addons.\n\n
{\n "targets": [\n {\n "target_name": "addon",\n "sources": [ "hello.cc" ]\n }\n ]\n}
\nNote: A version of the node-gyp
utility is bundled and distributed with\nNode.js as part of npm
. This version is not made directly available for\ndevelopers to use and is intended only to support the ability to use the\nnpm install
command to compile and install Addons. Developers who wish to\nuse node-gyp
directly can install it using the command\nnpm install -g node-gyp
. See the node-gyp
[installation instructions][] for\nmore information, including platform-specific requirements.\n\n
Once the binding.gyp
file has been created, use node-gyp configure
to\ngenerate the appropriate project build files for the current platform. This\nwill generate either a Makefile
(on Unix platforms) or a vcxproj
file\n(on Windows) in the build/
directory.\n\n
Next, invoke the node-gyp build
command to generate the compiled addon.node
\nfile. This will be put into the build/Release/
directory.\n\n
When using npm install
to install a Node.js Addon, npm uses its own bundled\nversion of node-gyp
to perform this same set of actions, generating a\ncompiled version of the Addon for the user's platform on demand.\n\n
Once built, the binary Addon can be used from within Node.js by pointing\n[require()
][require] to the built addon.node
module:\n\n
// hello.js\nconst addon = require('./build/Release/addon');\n\nconsole.log(addon.hello()); // 'world'
\nPlease see the examples below for further information or\n
\nhttps://github.com/arturadib/node-qt for an example in production.\n\n
\nBecause the exact path to the compiled Addon binary can vary depending on how\nit is compiled (i.e. sometimes it may be in ./build/Debug/
), Addons can use\nthe [bindings][] package to load the compiled module.\n\n
Note that while the bindings
package implementation is more sophisticated\nin how it locates Addon modules, it is essentially using a try-catch pattern\nsimilar to:\n\n
try {\n return require('./build/Release/addon.node');\n} catch (err) {\n return require('./build/Debug/addon.node');\n}
\n",
"type": "module",
"displayName": "Building"
},
{
"textRaw": "Linking to Node.js' own dependencies",
"name": "linking_to_node.js'_own_dependencies",
"desc": "Node.js uses a number of statically linked libraries such as V8, libuv and\nOpenSSL. All Addons are required to link to V8 and may link to any of the\nother dependencies as well. Typically, this is as simple as including\nthe appropriate #include <...>
statements (e.g. #include <v8.h>
) and\nnode-gyp
will locate the appropriate headers automatically. However, there\nare a few caveats to be aware of:\n\n
When node-gyp
runs, it will detect the specific release version of Node.js\nand download either the full source tarball or just the headers. If the full\nsource is downloaded, Addons will have complete access to the full set of\nNode.js dependencies. However, if only the Node.js headers are downloaded, then\nonly the symbols exported by Node.js will be available.
node-gyp
can be run using the --nodedir
flag pointing at a local Node.js\nsource image. Using this option, the Addon will have access to the full set of\ndependencies.
The filename extension of the compiled Addon binary is .node
(as opposed\nto .dll
or .so
). The [require()
][require] function is written to look for\nfiles with the .node
file extension and initialize those as dynamically-linked\nlibraries.\n\n
When calling [require()
][require], the .node
extension can usually be\nomitted and Node.js will still find and initialize the Addon. One caveat,\nhowever, is that Node.js will first attempt to locate and load modules or\nJavaScript files that happen to share the same base name. For instance, if\nthere is a file addon.js
in the same directory as the binary addon.node
,\nthen [require('addon')
][require] will give precedence to the addon.js
file\nand load it instead.\n\n
Following are some example Addons intended to help developers get started. The\nexamples make use of the V8 APIs. Refer to the online [V8 reference][v8-docs]\nfor help with the various V8 calls, and V8's [Embedder's Guide][] for an\nexplanation of several concepts used such as handles, scopes, function\ntemplates, etc.\n\n
\nEach of these examples using the following binding.gyp
file:\n\n
{\n "targets": [\n {\n "target_name": "addon",\n "sources": [ "addon.cc" ]\n }\n ]\n}
\nIn cases where there is more than one .cc
file, simply add the additional\nfilename to the sources
array. For example:\n\n
"sources": ["addon.cc", "myexample.cc"]
\nOnce the binding.gyp
file is ready, the example Addons can be configured and\nbuilt using node-gyp
:\n\n
$ node-gyp configure build
\n",
"modules": [
{
"textRaw": "Function arguments",
"name": "function_arguments",
"desc": "Addons will typically expose objects and functions that can be accessed from\nJavaScript running within Node.js. When functions are invoked from JavaScript,\nthe input arguments and return value must be mapped to and from the C/C++\ncode.\n\n
\nThe following example illustrates how to read function arguments passed from\nJavaScript and how to return a result:\n\n
\n// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::Exception;\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Number;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\n// This is the implementation of the "add" method\n// Input arguments are passed using the\n// const FunctionCallbackInfo<Value>& args struct\nvoid Add(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n // Check the number of arguments passed.\n if (args.Length() < 2) {\n // Throw an Error that is passed back to JavaScript\n isolate->ThrowException(Exception::TypeError(\n String::NewFromUtf8(isolate, "Wrong number of arguments")));\n return;\n }\n\n // Check the argument types\n if (!args[0]->IsNumber() || !args[1]->IsNumber()) {\n isolate->ThrowException(Exception::TypeError(\n String::NewFromUtf8(isolate, "Wrong arguments")));\n return;\n }\n\n // Perform the operation\n double value = args[0]->NumberValue() + args[1]->NumberValue();\n Local<Number> num = Number::New(isolate, value);\n\n // Set the return value (using the passed in\n // FunctionCallbackInfo<Value>&)\n args.GetReturnValue().Set(num);\n}\n\nvoid Init(Local<Object> exports) {\n NODE_SET_METHOD(exports, "add", Add);\n}\n\nNODE_MODULE(addon, Init)\n\n} // namespace demo
\nOnce compiled, the example Addon can be required and used from within Node.js:\n\n
\n// test.js\nconst addon = require('./build/Release/addon');\n\nconsole.log('This should be eight:', addon.add(3, 5));
\n",
"type": "module",
"displayName": "Function arguments"
},
{
"textRaw": "Callbacks",
"name": "callbacks",
"desc": "It is common practice within Addons to pass JavaScript functions to a C++\nfunction and execute them from there. The following example illustrates how\nto invoke such callbacks:\n\n
\n// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Null;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid RunCallback(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n Local<Function> cb = Local<Function>::Cast(args[0]);\n const unsigned argc = 1;\n Local<Value> argv[argc] = { String::NewFromUtf8(isolate, "hello world") };\n cb->Call(Null(isolate), argc, argv);\n}\n\nvoid Init(Local<Object> exports, Local<Object> module) {\n NODE_SET_METHOD(module, "exports", RunCallback);\n}\n\nNODE_MODULE(addon, Init)\n\n} // namespace demo
\nNote that this example uses a two-argument form of Init()
that receives\nthe full module
object as the second argument. This allows the Addon\nto completely overwrite exports
with a single function instead of\nadding the function as a property of exports
.\n\n
To test it, run the following JavaScript:\n\n
\n// test.js\nconst addon = require('./build/Release/addon');\n\naddon((msg) => {\n console.log(msg); // 'hello world'\n});
\nNote that, in this example, the callback function is invoked synchronously.\n\n
\n", "type": "module", "displayName": "Callbacks" }, { "textRaw": "Object factory", "name": "object_factory", "desc": "Addons can create and return new objects from within a C++ function as\nillustrated in the following example. An object is created and returned with a\nproperty msg
that echoes the string passed to createObject()
:\n\n
// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid CreateObject(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n Local<Object> obj = Object::New(isolate);\n obj->Set(String::NewFromUtf8(isolate, "msg"), args[0]->ToString());\n\n args.GetReturnValue().Set(obj);\n}\n\nvoid Init(Local<Object> exports, Local<Object> module) {\n NODE_SET_METHOD(module, "exports", CreateObject);\n}\n\nNODE_MODULE(addon, Init)\n\n} // namespace demo
\nTo test it in JavaScript:\n\n
\n// test.js\nconst addon = require('./build/Release/addon');\n\nvar obj1 = addon('hello');\nvar obj2 = addon('world');\nconsole.log(obj1.msg + ' ' + obj2.msg); // 'hello world'
\n",
"type": "module",
"displayName": "Object factory"
},
{
"textRaw": "Function factory",
"name": "function_factory",
"desc": "Another common scenario is creating JavaScript functions that wrap C++\nfunctions and returning those back to JavaScript:\n\n
\n// addon.cc\n#include <node.h>\n\nnamespace demo {\n\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid MyFunction(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n args.GetReturnValue().Set(String::NewFromUtf8(isolate, "hello world"));\n}\n\nvoid CreateFunction(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, MyFunction);\n Local<Function> fn = tpl->GetFunction();\n\n // omit this to make it anonymous\n fn->SetName(String::NewFromUtf8(isolate, "theFunction"));\n\n args.GetReturnValue().Set(fn);\n}\n\nvoid Init(Local<Object> exports, Local<Object> module) {\n NODE_SET_METHOD(module, "exports", CreateFunction);\n}\n\nNODE_MODULE(addon, Init)\n\n} // namespace demo
\nTo test:\n\n
\n// test.js\nconst addon = require('./build/Release/addon');\n\nvar fn = addon();\nconsole.log(fn()); // 'hello world'
\n",
"type": "module",
"displayName": "Function factory"
},
{
"textRaw": "Wrapping C++ objects",
"name": "wrapping_c++_objects",
"desc": "It is also possible to wrap C++ objects/classes in a way that allows new\ninstances to be created using the JavaScript new
operator:\n\n
// addon.cc\n#include <node.h>\n#include "myobject.h"\n\nnamespace demo {\n\nusing v8::Local;\nusing v8::Object;\n\nvoid InitAll(Local<Object> exports) {\n MyObject::Init(exports);\n}\n\nNODE_MODULE(addon, InitAll)\n\n} // namespace demo
\nThen, in myobject.h
, the wrapper class inherits from node::ObjectWrap
:\n\n
// myobject.h\n#ifndef MYOBJECT_H\n#define MYOBJECT_H\n\n#include <node.h>\n#include <node_object_wrap.h>\n\nnamespace demo {\n\nclass MyObject : public node::ObjectWrap {\n public:\n static void Init(v8::Local<v8::Object> exports);\n\n private:\n explicit MyObject(double value = 0);\n ~MyObject();\n\n static void New(const v8::FunctionCallbackInfo<v8::Value>& args);\n static void PlusOne(const v8::FunctionCallbackInfo<v8::Value>& args);\n static v8::Persistent<v8::Function> constructor;\n double value_;\n};\n\n} // namespace demo\n\n#endif
\nIn myobject.cc
, implement the various methods that are to be exposed.\nBelow, the method plusOne()
is exposed by adding it to the constructor's\nprototype:\n\n
// myobject.cc\n#include "myobject.h"\n\nnamespace demo {\n\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Number;\nusing v8::Object;\nusing v8::Persistent;\nusing v8::String;\nusing v8::Value;\n\nPersistent<Function> MyObject::constructor;\n\nMyObject::MyObject(double value) : value_(value) {\n}\n\nMyObject::~MyObject() {\n}\n\nvoid MyObject::Init(Local<Object> exports) {\n Isolate* isolate = exports->GetIsolate();\n\n // Prepare constructor template\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);\n tpl->SetClassName(String::NewFromUtf8(isolate, "MyObject"));\n tpl->InstanceTemplate()->SetInternalFieldCount(1);\n\n // Prototype\n NODE_SET_PROTOTYPE_METHOD(tpl, "plusOne", PlusOne);\n\n constructor.Reset(isolate, tpl->GetFunction());\n exports->Set(String::NewFromUtf8(isolate, "MyObject"),\n tpl->GetFunction());\n}\n\nvoid MyObject::New(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n if (args.IsConstructCall()) {\n // Invoked as constructor: `new MyObject(...)`\n double value = args[0]->IsUndefined() ? 0 : args[0]->NumberValue();\n MyObject* obj = new MyObject(value);\n obj->Wrap(args.This());\n args.GetReturnValue().Set(args.This());\n } else {\n // Invoked as plain function `MyObject(...)`, turn into construct call.\n const int argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n args.GetReturnValue().Set(cons->NewInstance(argc, argv));\n }\n}\n\nvoid MyObject::PlusOne(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n MyObject* obj = ObjectWrap::Unwrap<MyObject>(args.Holder());\n obj->value_ += 1;\n\n args.GetReturnValue().Set(Number::New(isolate, obj->value_));\n}\n\n} // namespace demo
\nTo build this example, the myobject.cc
file must be added to the\nbinding.gyp
:\n\n
{\n "targets": [\n {\n "target_name": "addon",\n "sources": [\n "addon.cc",\n "myobject.cc"\n ]\n }\n ]\n}
\nTest it with:\n\n
\n// test.js\nconst addon = require('./build/Release/addon');\n\nvar obj = new addon.MyObject(10);\nconsole.log(obj.plusOne()); // 11\nconsole.log(obj.plusOne()); // 12\nconsole.log(obj.plusOne()); // 13
\n",
"type": "module",
"displayName": "Wrapping C++ objects"
},
{
"textRaw": "Factory of wrapped objects",
"name": "factory_of_wrapped_objects",
"desc": "Alternatively, it is possible to use a factory pattern to avoid explicitly\ncreating object instances using the JavaScript new
operator:\n\n
var obj = addon.createObject();\n// instead of:\n// var obj = new addon.Object();
\nFirst, the createObject()
method is implemented in addon.cc
:\n\n
// addon.cc\n#include <node.h>\n#include "myobject.h"\n\nnamespace demo {\n\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid CreateObject(const FunctionCallbackInfo<Value>& args) {\n MyObject::NewInstance(args);\n}\n\nvoid InitAll(Local<Object> exports, Local<Object> module) {\n MyObject::Init(exports->GetIsolate());\n\n NODE_SET_METHOD(module, "exports", CreateObject);\n}\n\nNODE_MODULE(addon, InitAll)\n\n} // namespace demo
\nIn myobject.h
, the static method NewInstance()
is added to handle\ninstantiating the object. This method takes the place of using new
in\nJavaScript:\n\n
// myobject.h\n#ifndef MYOBJECT_H\n#define MYOBJECT_H\n\n#include <node.h>\n#include <node_object_wrap.h>\n\nnamespace demo {\n\nclass MyObject : public node::ObjectWrap {\n public:\n static void Init(v8::Isolate* isolate);\n static void NewInstance(const v8::FunctionCallbackInfo<v8::Value>& args);\n\n private:\n explicit MyObject(double value = 0);\n ~MyObject();\n\n static void New(const v8::FunctionCallbackInfo<v8::Value>& args);\n static void PlusOne(const v8::FunctionCallbackInfo<v8::Value>& args);\n static v8::Persistent<v8::Function> constructor;\n double value_;\n};\n\n} // namespace demo\n\n#endif
\nThe implementation in myobject.cc
is similar to the previous example:\n\n
// myobject.cc\n#include <node.h>\n#include "myobject.h"\n\nnamespace demo {\n\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Number;\nusing v8::Object;\nusing v8::Persistent;\nusing v8::String;\nusing v8::Value;\n\nPersistent<Function> MyObject::constructor;\n\nMyObject::MyObject(double value) : value_(value) {\n}\n\nMyObject::~MyObject() {\n}\n\nvoid MyObject::Init(Isolate* isolate) {\n // Prepare constructor template\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);\n tpl->SetClassName(String::NewFromUtf8(isolate, "MyObject"));\n tpl->InstanceTemplate()->SetInternalFieldCount(1);\n\n // Prototype\n NODE_SET_PROTOTYPE_METHOD(tpl, "plusOne", PlusOne);\n\n constructor.Reset(isolate, tpl->GetFunction());\n}\n\nvoid MyObject::New(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n if (args.IsConstructCall()) {\n // Invoked as constructor: `new MyObject(...)`\n double value = args[0]->IsUndefined() ? 0 : args[0]->NumberValue();\n MyObject* obj = new MyObject(value);\n obj->Wrap(args.This());\n args.GetReturnValue().Set(args.This());\n } else {\n // Invoked as plain function `MyObject(...)`, turn into construct call.\n const int argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n args.GetReturnValue().Set(cons->NewInstance(argc, argv));\n }\n}\n\nvoid MyObject::NewInstance(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n const unsigned argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n Local<Object> instance = cons->NewInstance(argc, argv);\n\n args.GetReturnValue().Set(instance);\n}\n\nvoid MyObject::PlusOne(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n MyObject* obj = ObjectWrap::Unwrap<MyObject>(args.Holder());\n obj->value_ += 1;\n\n args.GetReturnValue().Set(Number::New(isolate, obj->value_));\n}\n\n} // namespace demo
\nOnce again, to build this example, the myobject.cc
file must be added to the\nbinding.gyp
:\n\n
{\n "targets": [\n {\n "target_name": "addon",\n "sources": [\n "addon.cc",\n "myobject.cc"\n ]\n }\n ]\n}
\nTest it with:\n\n
\n// test.js\nconst createObject = require('./build/Release/addon');\n\nvar obj = createObject(10);\nconsole.log(obj.plusOne()); // 11\nconsole.log(obj.plusOne()); // 12\nconsole.log(obj.plusOne()); // 13\n\nvar obj2 = createObject(20);\nconsole.log(obj2.plusOne()); // 21\nconsole.log(obj2.plusOne()); // 22\nconsole.log(obj2.plusOne()); // 23
\n",
"type": "module",
"displayName": "Factory of wrapped objects"
},
{
"textRaw": "Passing wrapped objects around",
"name": "passing_wrapped_objects_around",
"desc": "In addition to wrapping and returning C++ objects, it is possible to pass\nwrapped objects around by unwrapping them with the Node.js helper function\nnode::ObjectWrap::Unwrap
. The following examples shows a function add()
\nthat can take two MyObject
objects as input arguments:\n\n
// addon.cc\n#include <node.h>\n#include <node_object_wrap.h>\n#include "myobject.h"\n\nnamespace demo {\n\nusing v8::FunctionCallbackInfo;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Number;\nusing v8::Object;\nusing v8::String;\nusing v8::Value;\n\nvoid CreateObject(const FunctionCallbackInfo<Value>& args) {\n MyObject::NewInstance(args);\n}\n\nvoid Add(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n MyObject* obj1 = node::ObjectWrap::Unwrap<MyObject>(\n args[0]->ToObject());\n MyObject* obj2 = node::ObjectWrap::Unwrap<MyObject>(\n args[1]->ToObject());\n\n double sum = obj1->value() + obj2->value();\n args.GetReturnValue().Set(Number::New(isolate, sum));\n}\n\nvoid InitAll(Local<Object> exports) {\n MyObject::Init(exports->GetIsolate());\n\n NODE_SET_METHOD(exports, "createObject", CreateObject);\n NODE_SET_METHOD(exports, "add", Add);\n}\n\nNODE_MODULE(addon, InitAll)\n\n} // namespace demo
\nIn myobject.h
, a new public method is added to allow access to private values\nafter unwrapping the object.\n\n
// myobject.h\n#ifndef MYOBJECT_H\n#define MYOBJECT_H\n\n#include <node.h>\n#include <node_object_wrap.h>\n\nnamespace demo {\n\nclass MyObject : public node::ObjectWrap {\n public:\n static void Init(v8::Isolate* isolate);\n static void NewInstance(const v8::FunctionCallbackInfo<v8::Value>& args);\n inline double value() const { return value_; }\n\n private:\n explicit MyObject(double value = 0);\n ~MyObject();\n\n static void New(const v8::FunctionCallbackInfo<v8::Value>& args);\n static v8::Persistent<v8::Function> constructor;\n double value_;\n};\n\n} // namespace demo\n\n#endif
\nThe implementation of myobject.cc
is similar to before:\n\n
// myobject.cc\n#include <node.h>\n#include "myobject.h"\n\nnamespace demo {\n\nusing v8::Function;\nusing v8::FunctionCallbackInfo;\nusing v8::FunctionTemplate;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\nusing v8::Persistent;\nusing v8::String;\nusing v8::Value;\n\nPersistent<Function> MyObject::constructor;\n\nMyObject::MyObject(double value) : value_(value) {\n}\n\nMyObject::~MyObject() {\n}\n\nvoid MyObject::Init(Isolate* isolate) {\n // Prepare constructor template\n Local<FunctionTemplate> tpl = FunctionTemplate::New(isolate, New);\n tpl->SetClassName(String::NewFromUtf8(isolate, "MyObject"));\n tpl->InstanceTemplate()->SetInternalFieldCount(1);\n\n constructor.Reset(isolate, tpl->GetFunction());\n}\n\nvoid MyObject::New(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n if (args.IsConstructCall()) {\n // Invoked as constructor: `new MyObject(...)`\n double value = args[0]->IsUndefined() ? 0 : args[0]->NumberValue();\n MyObject* obj = new MyObject(value);\n obj->Wrap(args.This());\n args.GetReturnValue().Set(args.This());\n } else {\n // Invoked as plain function `MyObject(...)`, turn into construct call.\n const int argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n args.GetReturnValue().Set(cons->NewInstance(argc, argv));\n }\n}\n\nvoid MyObject::NewInstance(const FunctionCallbackInfo<Value>& args) {\n Isolate* isolate = args.GetIsolate();\n\n const unsigned argc = 1;\n Local<Value> argv[argc] = { args[0] };\n Local<Function> cons = Local<Function>::New(isolate, constructor);\n Local<Object> instance = cons->NewInstance(argc, argv);\n\n args.GetReturnValue().Set(instance);\n}\n\n} // namespace demo
\nTest it with:\n\n
\n// test.js\nconst addon = require('./build/Release/addon');\n\nvar obj1 = addon.createObject(10);\nvar obj2 = addon.createObject(20);\nvar result = addon.add(obj1, obj2);\n\nconsole.log(result); // 30
\n",
"type": "module",
"displayName": "Passing wrapped objects around"
},
{
"textRaw": "AtExit hooks",
"name": "atexit_hooks",
"desc": "An "AtExit" hook is a function that is invoked after the Node.js event loop\nhas ended by before the JavaScript VM is terminated and Node.js shuts down.\n"AtExit" hooks are registered using the node::AtExit
API.\n\n
callback
: void (*)(void*)
- A pointer to the function to call at exit.args
: void*
- A pointer to pass to the callback at exit.Registers exit hooks that run after the event loop has ended but before the VM\nis killed.\n\n
\nAtExit takes two parameters: a pointer to a callback function to run at exit,\nand a pointer to untyped context data to be passed to that callback.\n\n
\nCallbacks are run in last-in first-out order.\n\n
\nThe following addon.cc
implements AtExit:\n\n
// addon.cc\n#undef NDEBUG\n#include <assert.h>\n#include <stdlib.h>\n#include <node.h>\n\nnamespace demo {\n\nusing node::AtExit;\nusing v8::HandleScope;\nusing v8::Isolate;\nusing v8::Local;\nusing v8::Object;\n\nstatic char cookie[] = "yum yum";\nstatic int at_exit_cb1_called = 0;\nstatic int at_exit_cb2_called = 0;\n\nstatic void at_exit_cb1(void* arg) {\n Isolate* isolate = static_cast<Isolate*>(arg);\n HandleScope scope(isolate);\n Local<Object> obj = Object::New(isolate);\n assert(!obj.IsEmpty()); // assert VM is still alive\n assert(obj->IsObject());\n at_exit_cb1_called++;\n}\n\nstatic void at_exit_cb2(void* arg) {\n assert(arg == static_cast<void*>(cookie));\n at_exit_cb2_called++;\n}\n\nstatic void sanity_check(void*) {\n assert(at_exit_cb1_called == 1);\n assert(at_exit_cb2_called == 2);\n}\n\nvoid init(Local<Object> exports) {\n AtExit(sanity_check);\n AtExit(at_exit_cb2, cookie);\n AtExit(at_exit_cb2, cookie);\n AtExit(at_exit_cb1, exports->GetIsolate());\n}\n\nNODE_MODULE(addon, init);\n\n} // namespace demo
\nTest in JavaScript by running:\n\n
\n// test.js\nconst addon = require('./build/Release/addon');
\n",
"type": "module",
"displayName": "void AtExit(callback, args)"
}
],
"type": "module",
"displayName": "AtExit hooks"
}
],
"type": "module",
"displayName": "Addon examples"
}
],
"properties": [
{
"textRaw": "Native Abstractions for Node.js",
"name": "js",
"desc": "Each of the examples illustrated in this document make direct use of the\nNode.js and V8 APIs for implementing Addons. It is important to understand\nthat the V8 API can, and has, changed dramatically from one V8 release to the\nnext (and one major Node.js release to the next). With each change, Addons may\nneed to be updated and recompiled in order to continue functioning. The Node.js\nrelease schedule is designed to minimize the frequency and impact of such\nchanges but there is little that Node.js can do currently to ensure stability\nof the V8 APIs.\n\n
\nThe [Native Abstractions for Node.js][] (or nan
) provide a set of tools that\nAddon developers are recommended to use to keep compatibility between past and\nfuture releases of V8 and Node.js. See the nan
[examples][] for an\nillustration of how it can be used.\n\n
The assert
module provides a simple set of assertion tests that can be used to\ntest invariants. The module is intended for internal use by Node.js, but can be\nused in application code via require('assert')
. However, assert
is not a\ntesting framework, and is not intended to be used as a general purpose assertion\nlibrary.\n\n
The API for the assert
module is [Locked][]. This means that there will be no\nadditions or changes to any of the methods implemented and exposed by\nthe module.\n\n
An alias of [assert.ok()
][] .\n\n
const assert = require('assert');\n\nassert(true); // OK\nassert(1); // OK\nassert(false);\n // throws "AssertionError: false == true"\nassert(0);\n // throws "AssertionError: 0 == true"\nassert(false, 'it\\'s false');\n // throws "AssertionError: it's false"
\n",
"signatures": [
{
"params": [
{
"name": "value"
},
{
"name": "message",
"optional": true
}
]
}
]
},
{
"textRaw": "assert.deepEqual(actual, expected[, message])",
"type": "method",
"name": "deepEqual",
"desc": "Tests for deep equality between the actual
and expected
parameters.\nPrimitive values are compared with the equal comparison operator ( ==
).\n\n
Only enumerable "own" properties are considered. The deepEqual()
\nimplementation does not test object prototypes, attached symbols, or\nnon-enumerable properties. This can lead to some potentially surprising\nresults. For example, the following example does not throw an AssertionError
\nbecause the properties on the [Error
][] object are non-enumerable:\n\n
// WARNING: This does not throw an AssertionError!\nassert.deepEqual(Error('a'), Error('b'));
\n"Deep" equality means that the enumerable "own" properties of child objects\nare evaluated also:\n\n
\nconst assert = require('assert');\n\nconst obj1 = {\n a : {\n b : 1\n }\n};\nconst obj2 = {\n a : {\n b : 2\n }\n};\nconst obj3 = {\n a : {\n b : 1\n }\n}\nconst obj4 = Object.create(obj1);\n\nassert.deepEqual(obj1, obj1);\n // OK, object is equal to itself\n\nassert.deepEqual(obj1, obj2);\n // AssertionError: { a: { b: 1 } } deepEqual { a: { b: 2 } }\n // values of b are different\n\nassert.deepEqual(obj1, obj3);\n // OK, objects are equal\n\nassert.deepEqual(obj1, obj4);\n // AssertionError: { a: { b: 1 } } deepEqual {}\n // Prototypes are ignored
\nIf the values are not equal, an AssertionError
is thrown with a message
\nproperty set equal to the value of the message
parameter. If the message
\nparameter is undefined, a default error message is assigned.\n\n
Generally identical to assert.deepEqual()
with two exceptions. First,\nprimitive values are compared using the strict equality operator ( ===
).\nSecond, object comparisons include a strict equality check of their prototypes.\n\n
const assert = require('assert');\n\nassert.deepEqual({a:1}, {a:'1'});\n // OK, because 1 == '1'\n\nassert.deepStrictEqual({a:1}, {a:'1'});\n // AssertionError: { a: 1 } deepStrictEqual { a: '1' }\n // because 1 !== '1' using strict equality
\nIf the values are not equal, an AssertionError
is thrown with a message
\nproperty set equal to the value of the message
parameter. If the message
\nparameter is undefined, a default error message is assigned.\n\n
Asserts that the function block
does not throw an error. See\n[assert.throws()
][] for more details.\n\n
When assert.doesNotThrow()
is called, it will immediately call the block
\nfunction.\n\n
If an error is thrown and it is the same type as that specified by the error
\nparameter, then an AssertionError
is thrown. If the error is of a different\ntype, or if the error
parameter is undefined, the error is propagated back\nto the caller.\n\n
The following, for instance, will throw the [TypeError
][] because there is no\nmatching error type in the assertion:\n\n
assert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n SyntaxError\n);
\nHowever, the following will result in an AssertionError
with the message\n'Got unwanted exception (TypeError)..':\n\n
assert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n TypeError\n);
\nIf an AssertionError
is thrown and a value is provided for the message
\nparameter, the value of message
will be appended to the AssertionError
\nmessage:\n\n
assert.doesNotThrow(\n () => {\n throw new TypeError('Wrong value');\n },\n TypeError,\n 'Whoops'\n);\n// Throws: AssertionError: Got unwanted exception (TypeError). Whoops
\n",
"signatures": [
{
"params": [
{
"name": "block"
},
{
"name": "error",
"optional": true
},
{
"name": "message",
"optional": true
}
]
}
]
},
{
"textRaw": "assert.equal(actual, expected[, message])",
"type": "method",
"name": "equal",
"desc": "Tests shallow, coercive equality between the actual
and expected
parameters\nusing the equal comparison operator ( ==
).\n\n
const assert = require('assert');\n\nassert.equal(1, 1);\n // OK, 1 == 1\nassert.equal(1, '1');\n // OK, 1 == '1'\n\nassert.equal(1, 2);\n // AssertionError: 1 == 2\nassert.equal({a: {b: 1}}, {a: {b: 1}});\n //AssertionError: { a: { b: 1 } } == { a: { b: 1 } }
\nIf the values are not equal, an AssertionError
is thrown with a message
\nproperty set equal to the value of the message
parameter. If the message
\nparameter is undefined, a default error message is assigned.\n\n
Throws an AssertionError
. If message
is falsy, the error message is set as\nthe values of actual
and expected
separated by the provided operator
.\nOtherwise, the error message is the value of message
.\n\n
const assert = require('assert');\n\nassert.fail(1, 2, undefined, '>');\n // AssertionError: 1 > 2\n\nassert.fail(1, 2, 'whoops', '>');\n // AssertionError: whoops
\n",
"signatures": [
{
"params": [
{
"name": "actual"
},
{
"name": "expected"
},
{
"name": "message"
},
{
"name": "operator"
}
]
}
]
},
{
"textRaw": "assert.ifError(value)",
"type": "method",
"name": "ifError",
"desc": "Throws value
if value
is truthy. This is useful when testing the error
\nargument in callbacks.\n\n
const assert = require('assert');\n\nassert.ifError(0); // OK\nassert.ifError(1); // Throws 1\nassert.ifError('error') // Throws 'error'\nassert.ifError(new Error()); // Throws Error
\n",
"signatures": [
{
"params": [
{
"name": "value"
}
]
}
]
},
{
"textRaw": "assert.notDeepEqual(actual, expected[, message])",
"type": "method",
"name": "notDeepEqual",
"desc": "Tests for any deep inequality. Opposite of [assert.deepEqual()
][].\n\n
const assert = require('assert');\n\nconst obj1 = {\n a : {\n b : 1\n }\n};\nconst obj2 = {\n a : {\n b : 2\n }\n};\nconst obj3 = {\n a : {\n b : 1\n }\n}\nconst obj4 = Object.create(obj1);\n\nassert.notDeepEqual(obj1, obj1);\n // AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }\n\nassert.notDeepEqual(obj1, obj2);\n // OK, obj1 and obj2 are not deeply equal\n\nassert.notDeepEqual(obj1, obj3);\n // AssertionError: { a: { b: 1 } } notDeepEqual { a: { b: 1 } }\n\nassert.notDeepEqual(obj1, obj4);\n // OK, obj1 and obj2 are not deeply equal
\nIf the values are deeply equal, an AssertionError
is thrown with a message
\nproperty set equal to the value of the message
parameter. If the message
\nparameter is undefined, a default error message is assigned.\n\n
Tests for deep strict inequality. Opposite of [assert.deepStrictEqual()
][].\n\n
const assert = require('assert');\n\nassert.notDeepEqual({a:1}, {a:'1'});\n // AssertionError: { a: 1 } notDeepEqual { a: '1' }\n\nassert.notDeepStrictEqual({a:1}, {a:'1'});\n // OK
\nIf the values are deeply and strictly equal, an AssertionError
is thrown\nwith a message
property set equal to the value of the message
parameter. If\nthe message
parameter is undefined, a default error message is assigned.\n\n
Tests shallow, coercive inequality with the not equal comparison operator\n( !=
).\n\n
const assert = require('assert');\n\nassert.notEqual(1, 2);\n // OK\n\nassert.notEqual(1, 1);\n // AssertionError: 1 != 1\n\nassert.notEqual(1, '1');\n // AssertionError: 1 != '1'
\nIf the values are equal, an AssertionError
is thrown with a message
\nproperty set equal to the value of the message
parameter. If the message
\nparameter is undefined, a default error message is assigned.\n\n
Tests strict inequality as determined by the strict not equal operator\n( !==
).\n\n
const assert = require('assert');\n\nassert.notStrictEqual(1, 2);\n // OK\n\nassert.notStrictEqual(1, 1);\n // AssertionError: 1 != 1\n\nassert.notStrictEqual(1, '1');\n // OK
\nIf the values are strictly equal, an AssertionError
is thrown with a\nmessage
property set equal to the value of the message
parameter. If the\nmessage
parameter is undefined, a default error message is assigned.\n\n
Tests if value
is truthy. It is equivalent to\nassert.equal(!!value, true, message)
.\n\n
If value
is not truthy, an AssertionError
is thrown with a message
\nproperty set equal to the value of the message
parameter. If the message
\nparameter is undefined
, a default error message is assigned.\n\n
const assert = require('assert');\n\nassert.ok(true); // OK\nassert.ok(1); // OK\nassert.ok(false);\n // throws "AssertionError: false == true"\nassert.ok(0);\n // throws "AssertionError: 0 == true"\nassert.ok(false, 'it\\'s false');\n // throws "AssertionError: it's false"
\n",
"signatures": [
{
"params": [
{
"name": "value"
},
{
"name": "message",
"optional": true
}
]
}
]
},
{
"textRaw": "assert.strictEqual(actual, expected[, message])",
"type": "method",
"name": "strictEqual",
"desc": "Tests strict equality as determined by the strict equality operator ( ===
).\n\n
const assert = require('assert');\n\nassert.strictEqual(1, 2);\n // AssertionError: 1 === 2\n\nassert.strictEqual(1, 1);\n // OK\n\nassert.strictEqual(1, '1');\n // AssertionError: 1 === '1'
\nIf the values are not strictly equal, an AssertionError
is thrown with a\nmessage
property set equal to the value of the message
parameter. If the\nmessage
parameter is undefined, a default error message is assigned.\n\n
Expects the function block
to throw an error.\n\n
If specified, error
can be a constructor, [RegExp
][], or validation\nfunction.\n\n
If specified, message
will be the message provided by the AssertionError
if\nthe block fails to throw.\n\n
Validate instanceof using constructor:\n\n
\nassert.throws(\n () => {\n throw new Error('Wrong value');\n },\n Error\n);
\nValidate error message using [RegExp
][]:\n\n
assert.throws(\n () => {\n throw new Error('Wrong value');\n },\n /value/\n);
\nCustom error validation:\n\n
\nassert.throws(\n () => {\n throw new Error('Wrong value');\n },\n function(err) {\n if ( (err instanceof Error) && /value/.test(err) ) {\n return true;\n }\n },\n 'unexpected error'\n);
\nNote that error
can not be a string. If a string is provided as the second\nargument, then error
is assumed to be omitted and the string will be used for\nmessage
instead. This can lead to easy-to-miss mistakes:\n\n
// THIS IS A MISTAKE! DO NOT DO THIS!\nassert.throws(myFunction, 'missing foo', 'did not throw with expected message');\n\n// Do this instead.\nassert.throws(myFunction, /missing foo/, 'did not throw with expected message');
\n",
"signatures": [
{
"params": [
{
"name": "block"
},
{
"name": "error",
"optional": true
},
{
"name": "message",
"optional": true
}
]
}
]
}
],
"type": "module",
"displayName": "Assert"
},
{
"textRaw": "Buffer",
"name": "buffer",
"stability": 2,
"stabilityText": "Stable",
"desc": "Prior to the introduction of TypedArray
in ECMAScript 2015 (ES6), the\nJavaScript language had no mechanism for reading or manipulating streams\nof binary data. The Buffer
class was introduced as part of the Node.js\nAPI to make it possible to interact with octet streams in the context of things\nlike TCP streams and file system operations.\n\n
Now that TypedArray
has been added in ES6, the Buffer
class implements the\nUint8Array
API in a manner that is more optimized and suitable for Node.js'\nuse cases.\n\n
Instances of the Buffer
class are similar to arrays of integers but\ncorrespond to fixed-sized, raw memory allocations outside the V8 heap.\nThe size of the Buffer
is established when it is created and cannot be\nresized.\n\n
The Buffer
class is a global within Node.js, making it unlikely that one\nwould need to ever use require('buffer')
.\n\n
const buf1 = Buffer.alloc(10);\n // Creates a zero-filled Buffer of length 10.\n\nconst buf2 = Buffer.alloc(10, 1);\n // Creates a Buffer of length 10, filled with 0x01.\n\nconst buf3 = Buffer.allocUnsafe(10);\n // Creates an uninitialized buffer of length 10.\n // This is faster than calling Buffer.alloc() but the returned\n // Buffer instance might contain old data that needs to be\n // overwritten using either fill() or write().\n\nconst buf4 = Buffer.from([1,2,3]);\n // Creates a Buffer containing [01, 02, 03].\n\nconst buf5 = Buffer.from('test');\n // Creates a Buffer containing ASCII bytes [74, 65, 73, 74].\n\nconst buf6 = Buffer.from('tést', 'utf8');\n // Creates a Buffer containing UTF8 bytes [74, c3, a9, 73, 74].
\n",
"modules": [
{
"textRaw": "`Buffer.from()`, `Buffer.alloc()`, and `Buffer.allocUnsafe()`",
"name": "`buffer.from()`,_`buffer.alloc()`,_and_`buffer.allocunsafe()`",
"desc": "In versions of Node.js prior to v6, Buffer
instances were created using the\nBuffer
constructor function, which allocates the returned Buffer
\ndifferently based on what arguments are provided:\n\n
Buffer()
(e.g. new Buffer(10)
),\nallocates a new Buffer
object of the specified size. The memory allocated\nfor such Buffer
instances is not initialized and can contain sensitive\ndata. Such Buffer
objects must be initialized manually by using either\n[buf.fill(0)
][] or by writing to the Buffer
completely. While this\nbehavior is intentional to improve performance, development experience has\ndemonstrated that a more explicit distinction is required between creating a\nfast-but-uninitialized Buffer
versus creating a slower-but-safer Buffer
.Buffer
as the first argument copies the\npassed object's data into the Buffer
.ArrayBuffer
returns a Buffer
that shares allocated memory with\nthe given ArrayBuffer
.Because the behavior of new Buffer()
changes significantly based on the type\nof value passed as the first argument, applications that do not properly\nvalidate the input arguments passed to new Buffer()
, or that fail to\nappropriately initialize newly allocated Buffer
content, can inadvertently\nintroduce security and reliability issues into their code.\n\n
To make the creation of Buffer
objects more reliable and less error prone,\nthe various forms of the new Buffer()
constructor have been deprecated\nand replaced by separate Buffer.from()
, Buffer.alloc()
, and\nBuffer.allocUnsafe()
methods.\n\n
Developers should migrate all existing uses of the new Buffer()
constructors\nto one of these new APIs.\n\n
Buffer.from(array)
][buffer_from_array] returns a new Buffer
containing\na copy of the provided octets.Buffer.from(arrayBuffer[, byteOffset [, length]])
][buffer_from_arraybuf]\nreturns a new Buffer
that shares the same allocated memory as the given\nArrayBuffer
.Buffer.from(buffer)
][buffer_from_buffer] returns a new Buffer
\ncontaining a copy of the contents of the given Buffer
.Buffer.from(str[, encoding])
][buffer_from_string] returns a new Buffer
\ncontaining a copy of the provided string.Buffer.alloc(size[, fill[, encoding]])
][buffer_alloc] returns a "filled"\nBuffer
instance of the specified size. This method can be significantly\nslower than [Buffer.allocUnsafe(size)
][buffer_allocunsafe] but ensures\nthat newly created Buffer
instances never contain old and potentially\nsensitive data.Buffer.allocUnsafe(size)
][buffer_allocunsafe] and\n[Buffer.allocUnsafeSlow(size)
][buffer_allocunsafeslow] each return a\nnew Buffer
of the specified size
whose content must be initialized\nusing either [buf.fill(0)
][] or written to completely.Buffer
instances returned by Buffer.allocUnsafe(size)
may be allocated\noff a shared internal memory pool if size
is less than or equal to half\nBuffer.poolSize
. Instances returned by Buffer.allocUnsafeSlow(size)
never\nuse the shared internal memory pool.\n\n
Node.js can be started using the --zero-fill-buffers
command line option to\nforce all newly allocated Buffer
instances created using either\nnew Buffer(size)
, Buffer.allocUnsafe(size)
, Buffer.allocUnsafeSlow(size)
\nor new SlowBuffer(size)
to be automatically zero-filled upon creation. Use\nof this flag changes the default behavior of these methods and can have a\nsignificant impact on performance. Use of the --zero-fill-buffers
option is\nrecommended only when absolutely necessary to enforce that newly allocated\nBuffer
instances cannot contain potentially sensitive data.\n\n
$ node --zero-fill-buffers\n> Buffer.allocUnsafe(5);\n<Buffer 00 00 00 00 00>
\n",
"type": "module",
"displayName": "The `--zero-fill-buffers` command line option"
},
{
"textRaw": "What makes `Buffer.allocUnsafe(size)` and `Buffer.allocUnsafeSlow(size)` \"unsafe\"?",
"name": "what_makes_`buffer.allocunsafe(size)`_and_`buffer.allocunsafeslow(size)`_\"unsafe\"?",
"desc": "When calling Buffer.allocUnsafe()
(and Buffer.allocUnsafeSlow()
), the\nsegment of allocated memory is uninitialized (it is not zeroed-out). While\nthis design makes the allocation of memory quite fast, the allocated segment of\nmemory might contain old data that is potentially sensitive. Using a Buffer
\ncreated by Buffer.allocUnsafe()
without completely overwriting the memory\ncan allow this old data to be leaked when the Buffer
memory is read.\n\n
While there are clear performance advantages to using Buffer.allocUnsafe()
,\nextra care must be taken in order to avoid introducing security\nvulnerabilities into an application.\n\n
Buffers are commonly used to represent sequences of encoded characters\nsuch as UTF8, UCS2, Base64 or even Hex-encoded data. It is possible to\nconvert back and forth between Buffers and ordinary JavaScript string objects\nby using an explicit encoding method.\n\n
\nconst buf = Buffer.from('hello world', 'ascii');\nconsole.log(buf.toString('hex'));\n // prints: 68656c6c6f20776f726c64\nconsole.log(buf.toString('base64'));\n // prints: aGVsbG8gd29ybGQ=
\nThe character encodings currently supported by Node.js include:\n\n
\n'ascii'
- for 7-bit ASCII data only. This encoding method is very fast and\nwill strip the high bit if set.
'utf8'
- Multibyte encoded Unicode characters. Many web pages and other\ndocument formats use UTF-8.
'utf16le'
- 2 or 4 bytes, little-endian encoded Unicode characters.\nSurrogate pairs (U+10000 to U+10FFFF) are supported.
'ucs2'
- Alias of 'utf16le'
.
'base64'
- Base64 string encoding. When creating a buffer from a string,\nthis encoding will also correctly accept "URL and Filename Safe Alphabet" as\nspecified in [RFC 4648, Section 5].
'binary'
- A way of encoding the buffer into a one-byte (latin-1
)\nencoded string. The string 'latin-1'
is not supported. Instead, pass\n'binary'
to use 'latin-1'
encoding.
'hex'
- Encode each byte as two hexadecimal characters.
Buffers are also Uint8Array
TypedArray instances. However, there are subtle\nincompatibilities with the TypedArray specification in ECMAScript 2015. For\ninstance, while ArrayBuffer#slice()
creates a copy of the slice,\nthe implementation of [Buffer#slice()
][buf.slice()
] creates a view over the\nexisting Buffer without copying, making Buffer#slice()
far more efficient.\n\n
It is also possible to create new TypedArray instances from a Buffer
with the\nfollowing caveats:\n\n
The Buffer
object's memory is copied to the TypedArray, not shared.
The Buffer
object's memory is interpreted as an array of distinct\nelements, and not as a byte array of the target type. That is,\nnew Uint32Array(Buffer.from([1,2,3,4]))
creates a 4-element Uint32Array
\nwith elements [1,2,3,4]
, not a Uint32Array
with a single element\n[0x1020304]
or [0x4030201]
.
It is possible to create a new Buffer
that shares the same allocated memory as\na TypedArray instance by using the TypeArray object's .buffer
property:\n\n
const arr = new Uint16Array(2);\narr[0] = 5000;\narr[1] = 4000;\n\nconst buf1 = Buffer.from(arr); // copies the buffer\nconst buf2 = Buffer.from(arr.buffer); // shares the memory with arr;\n\nconsole.log(buf1);\n // Prints: <Buffer 88 a0>, copied buffer has only two elements\nconsole.log(buf2);\n // Prints: <Buffer 88 13 a0 0f>\n\narr[1] = 6000;\nconsole.log(buf1);\n // Prints: <Buffer 88 a0>\nconsole.log(buf2);\n // Prints: <Buffer 88 13 70 17>
\nNote that when creating a Buffer
using the TypedArray's .buffer
, it is\npossible to use only a portion of the underlying ArrayBuffer
by passing in\nbyteOffset
and length
parameters:\n\n
const arr = new Uint16Array(20);\nconst buf = Buffer.from(arr.buffer, 0, 16);\nconsole.log(buf.length);\n // Prints: 16
\nThe Buffer.from()
and [TypedArray.from()
][] (e.g.Uint8Array.from()
) have\ndifferent signatures and implementations. Specifically, the TypedArray variants\naccept a second argument that is a mapping function that is invoked on every\nelement of the typed array:\n\n
TypedArray.from(source[, mapFn[, thisArg]])
The Buffer.from()
method, however, does not support the use of a mapping\nfunction:\n\n
Buffer.from(array)
][buffer_from_array]Buffer.from(buffer)
][buffer_from_buffer]Buffer.from(arrayBuffer[, byteOffset [, length]])
][buffer_from_arraybuf]Buffer.from(str[, encoding])
][buffer_from_string]Buffers can be iterated over using the ECMAScript 2015 (ES6) for..of
syntax:\n\n
const buf = Buffer.from([1, 2, 3]);\n\nfor (var b of buf)\n console.log(b)\n\n// Prints:\n// 1\n// 2\n// 3
\nAdditionally, the [buf.values()
][], [buf.keys()
][], and\n[buf.entries()
][] methods can be used to create iterators.\n\n
The Buffer class is a global type for dealing with binary data directly.\nIt can be constructed in a variety of ways.\n\n
\n", "classMethods": [ { "textRaw": "Class Method: Buffer.alloc(size[, fill[, encoding]])", "type": "classMethod", "name": "alloc", "signatures": [ { "params": [ { "textRaw": "`size` {Number} ", "name": "size", "type": "Number" }, { "textRaw": "`fill` {Value} Default: `undefined` ", "name": "fill", "type": "Value", "desc": "Default: `undefined`", "optional": true }, { "textRaw": "`encoding` {String} Default: `utf8` ", "name": "encoding", "type": "String", "desc": "Default: `utf8`", "optional": true } ] }, { "params": [ { "name": "size" }, { "name": "fill", "optional": true }, { "name": "encoding", "optional": true } ] } ], "desc": "Allocates a new Buffer
of size
bytes. If fill
is undefined
, the\nBuffer
will be zero-filled.\n\n
const buf = Buffer.alloc(5);\nconsole.log(buf);\n // <Buffer 00 00 00 00 00>
\nThe size
must be less than or equal to the value of\nrequire('buffer').kMaxLength
(on 64-bit architectures, kMaxLength
is\n(2^31)-1
). Otherwise, a [RangeError
][] is thrown. A zero-length Buffer will\nbe created if a size
less than or equal to 0 is specified.\n\n
If fill
is specified, the allocated Buffer
will be initialized by calling\nbuf.fill(fill)
. See [buf.fill()
][] for more information.\n\n
const buf = Buffer.alloc(5, 'a');\nconsole.log(buf);\n // <Buffer 61 61 61 61 61>
\nIf both fill
and encoding
are specified, the allocated Buffer
will be\ninitialized by calling buf.fill(fill, encoding)
. For example:\n\n
const buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');\nconsole.log(buf);\n // <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>
\nCalling Buffer.alloc(size)
can be significantly slower than the alternative\nBuffer.allocUnsafe(size)
but ensures that the newly created Buffer
instance\ncontents will never contain sensitive data.\n\n
A TypeError
will be thrown if size
is not a number.\n\n
Allocates a new non-zero-filled Buffer
of size
bytes. The size
must\nbe less than or equal to the value of require('buffer').kMaxLength
(on 64-bit\narchitectures, kMaxLength
is (2^31)-1
). Otherwise, a [RangeError
][] is\nthrown. A zero-length Buffer will be created if a size
less than or equal to\n0 is specified.\n\n
The underlying memory for Buffer
instances created in this way is not\ninitialized. The contents of the newly created Buffer
are unknown and\nmay contain sensitive data. Use [buf.fill(0)
][] to initialize such\nBuffer
instances to zeroes.\n\n
const buf = Buffer.allocUnsafe(5);\nconsole.log(buf);\n // <Buffer 78 e0 82 02 01>\n // (octets will be different, every time)\nbuf.fill(0);\nconsole.log(buf);\n // <Buffer 00 00 00 00 00>
\nA TypeError
will be thrown if size
is not a number.\n\n
Note that the Buffer
module pre-allocates an internal Buffer
instance of\nsize Buffer.poolSize
that is used as a pool for the fast allocation of new\nBuffer
instances created using Buffer.allocUnsafe(size)
(and the deprecated\nnew Buffer(size)
constructor) only when size
is less than or equal to\nBuffer.poolSize >> 1
(floor of Buffer.poolSize
divided by two). The default\nvalue of Buffer.poolSize
is 8192
but can be modified.\n\n
Use of this pre-allocated internal memory pool is a key difference between\ncalling Buffer.alloc(size, fill)
vs. Buffer.allocUnsafe(size).fill(fill)
.\nSpecifically, Buffer.alloc(size, fill)
will never use the internal Buffer\npool, while Buffer.allocUnsafe(size).fill(fill)
will use the internal\nBuffer pool if size
is less than or equal to half Buffer.poolSize
. The\ndifference is subtle but can be important when an application requires the\nadditional performance that Buffer.allocUnsafe(size)
provides.\n\n
Allocates a new non-zero-filled and non-pooled Buffer
of size
bytes. The\nsize
must be less than or equal to the value of\nrequire('buffer').kMaxLength
(on 64-bit architectures, kMaxLength
is\n(2^31)-1
). Otherwise, a [RangeError
][] is thrown. A zero-length Buffer will\nbe created if a size
less than or equal to 0 is specified.\n\n
The underlying memory for Buffer
instances created in this way is not\ninitialized. The contents of the newly created Buffer
are unknown and\nmay contain sensitive data. Use [buf.fill(0)
][] to initialize such\nBuffer
instances to zeroes.\n\n
When using Buffer.allocUnsafe()
to allocate new Buffer
instances,\nallocations under 4KB are, by default, sliced from a single pre-allocated\nBuffer
. This allows applications to avoid the garbage collection overhead of\ncreating many individually allocated Buffers. This approach improves both\nperformance and memory usage by eliminating the need to track and cleanup as\nmany Persistent
objects.\n\n
However, in the case where a developer may need to retain a small chunk of\nmemory from a pool for an indeterminate amount of time, it may be appropriate\nto create an un-pooled Buffer instance using Buffer.allocUnsafeSlow()
then\ncopy out the relevant bits.\n\n
// need to keep around a few small chunks of memory\nconst store = [];\n\nsocket.on('readable', () => {\n const data = socket.read();\n // allocate for retained data\n const sb = Buffer.allocUnsafeSlow(10);\n // copy the data into the new allocation\n data.copy(sb, 0, 0, 10);\n store.push(sb);\n});
\nUse of Buffer.allocUnsafeSlow()
should be used only as a last resort after\na developer has observed undue memory retention in their applications.\n\n
A TypeError
will be thrown if size
is not a number.\n\n
Returns the actual byte length of a string. This is not the same as\n[String.prototype.length
][] since that returns the number of characters in\na string.\n\n
Example:\n\n
\nconst str = '\\u00bd + \\u00bc = \\u00be';\n\nconsole.log(`${str}: ${str.length} characters, ` +\n `${Buffer.byteLength(str, 'utf8')} bytes`);\n\n// ½ + ¼ = ¾: 9 characters, 12 bytes
\nWhen string
is a Buffer
/[DataView
][]/[TypedArray
][]/ArrayBuffer
,\nreturns the actual byte length.\n\n
Otherwise, converts to String
and returns the byte length of string.\n\n
Compares buf1
to buf2
typically for the purpose of sorting arrays of\nBuffers. This is equivalent is calling [buf1.compare(buf2)
][].\n\n
const arr = [Buffer.from('1234'), Buffer.from('0123')];\narr.sort(Buffer.compare);
\n"
},
{
"textRaw": "Class Method: Buffer.concat(list[, totalLength])",
"type": "classMethod",
"name": "concat",
"signatures": [
{
"return": {
"textRaw": "Return: {Buffer} ",
"name": "return",
"type": "Buffer"
},
"params": [
{
"textRaw": "`list` {Array} List of Buffer objects to concat ",
"name": "list",
"type": "Array",
"desc": "List of Buffer objects to concat"
},
{
"textRaw": "`totalLength` {Number} Total length of the Buffers in the list when concatenated ",
"name": "totalLength",
"type": "Number",
"desc": "Total length of the Buffers in the list when concatenated",
"optional": true
}
]
},
{
"params": [
{
"name": "list"
},
{
"name": "totalLength",
"optional": true
}
]
}
],
"desc": "Returns a new Buffer which is the result of concatenating all the Buffers in\nthe list
together.\n\n
If the list has no items, or if the totalLength
is 0, then a new zero-length\nBuffer is returned.\n\n
If totalLength
is not provided, it is calculated from the Buffers in the\nlist
. This, however, adds an additional loop to the function, so it is faster\nto provide the length explicitly.\n\n
Example: build a single Buffer from a list of three Buffers:\n\n
\nconst buf1 = Buffer.alloc(10);\nconst buf2 = Buffer.alloc(14);\nconst buf3 = Buffer.alloc(18);\nconst totalLength = buf1.length + buf2.length + buf3.length;\n\nconsole.log(totalLength);\nconst bufA = Buffer.concat([buf1, buf2, buf3], totalLength);\nconsole.log(bufA);\nconsole.log(bufA.length);\n\n// 42\n// <Buffer 00 00 00 00 ...>\n// 42
\n"
},
{
"textRaw": "Class Method: Buffer.from(array)",
"type": "classMethod",
"name": "from",
"signatures": [
{
"params": [
{
"textRaw": "`array` {Array} ",
"name": "array",
"type": "Array"
}
]
},
{
"params": [
{
"name": "array"
}
]
}
],
"desc": "Allocates a new Buffer
using an array
of octets.\n\n
const buf = Buffer.from([0x62,0x75,0x66,0x66,0x65,0x72]);\n // creates a new Buffer containing ASCII bytes\n // ['b','u','f','f','e','r']
\nA TypeError
will be thrown if array
is not an Array
.\n\n
When passed a reference to the .buffer
property of a TypedArray
instance,\nthe newly created Buffer
will share the same allocated memory as the\nTypedArray.\n\n
const arr = new Uint16Array(2);\narr[0] = 5000;\narr[1] = 4000;\n\nconst buf = Buffer.from(arr.buffer); // shares the memory with arr;\n\nconsole.log(buf);\n // Prints: <Buffer 88 13 a0 0f>\n\n// changing the TypedArray changes the Buffer also\narr[1] = 6000;\n\nconsole.log(buf);\n // Prints: <Buffer 88 13 70 17>
\nThe optional byteOffset
and length
arguments specify a memory range within\nthe arrayBuffer
that will be shared by the Buffer
.\n\n
const ab = new ArrayBuffer(10);\nconst buf = Buffer.from(ab, 0, 2);\nconsole.log(buf.length);\n // Prints: 2
\nA TypeError
will be thrown if arrayBuffer
is not an ArrayBuffer
.\n\n
Copies the passed buffer
data onto a new Buffer
instance.\n\n
const buf1 = Buffer.from('buffer');\nconst buf2 = Buffer.from(buf1);\n\nbuf1[0] = 0x61;\nconsole.log(buf1.toString());\n // 'auffer'\nconsole.log(buf2.toString());\n // 'buffer' (copy is not changed)
\nA TypeError
will be thrown if buffer
is not a Buffer
.\n\n
Creates a new Buffer
containing the given JavaScript string str
. If\nprovided, the encoding
parameter identifies the character encoding.\nIf not provided, encoding
defaults to 'utf8'
.\n\n
const buf1 = Buffer.from('this is a tést');\nconsole.log(buf1.toString());\n // prints: this is a tést\nconsole.log(buf1.toString('ascii'));\n // prints: this is a tC)st\n\nconst buf2 = Buffer.from('7468697320697320612074c3a97374', 'hex');\nconsole.log(buf2.toString());\n // prints: this is a tést
\nA TypeError
will be thrown if str
is not a string.\n\n
Returns 'true' if obj
is a Buffer.\n\n
Returns true if the encoding
is a valid encoding argument, or false\notherwise.\n\n
The index operator [index]
can be used to get and set the octet at position\nindex
in the Buffer. The values refer to individual bytes, so the legal value\nrange is between 0x00
and 0xFF
(hex) or 0
and 255
(decimal).\n\n
Example: copy an ASCII string into a Buffer, one byte at a time:\n\n
\nconst str = "Node.js";\nconst buf = Buffer.allocUnsafe(str.length);\n\nfor (let i = 0; i < str.length ; i++) {\n buf[i] = str.charCodeAt(i);\n}\n\nconsole.log(buf.toString('ascii'));\n // Prints: Node.js
\n"
},
{
"textRaw": "`length` {Number} ",
"type": "Number",
"name": "length",
"desc": "Returns the amount of memory allocated for the Buffer in number of bytes. Note\nthat this does not necessarily reflect the amount of usable data within the\nBuffer. For instance, in the example below, a Buffer with 1234 bytes is\nallocated, but only 11 ASCII bytes are written.\n\n
\nconst buf = Buffer.alloc(1234);\n\nconsole.log(buf.length);\n // Prints: 1234\n\nbuf.write('some string', 0, 'ascii');\nconsole.log(buf.length);\n // Prints: 1234
\nWhile the length
property is not immutable, changing the value of length
\ncan result in undefined and inconsistent behavior. Applications that wish to\nmodify the length of a Buffer should therefore treat length
as read-only and\nuse [buf.slice()
][] to create a new Buffer.\n\n
var buf = Buffer.allocUnsafe(10);\nbuf.write('abcdefghj', 0, 'ascii');\nconsole.log(buf.length);\n // Prints: 10\nbuf = buf.slice(0,5);\nconsole.log(buf.length);\n // Prints: 5
\n"
}
],
"methods": [
{
"textRaw": "buf.compare(target[, targetStart[, targetEnd[, sourceStart[, sourceEnd]]]])",
"type": "method",
"name": "compare",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`target` {Buffer} ",
"name": "target",
"type": "Buffer"
},
{
"textRaw": "`targetStart` {Integer} The offset within `target` at which to begin comparison. default = `0`. ",
"name": "targetStart",
"type": "Integer",
"desc": "The offset within `target` at which to begin comparison. default = `0`.",
"optional": true
},
{
"textRaw": "`targetEnd` {Integer} The offset with `target` at which to end comparison. Ignored when `targetStart` is `undefined`. default = `target.byteLength`. ",
"name": "targetEnd",
"type": "Integer",
"desc": "The offset with `target` at which to end comparison. Ignored when `targetStart` is `undefined`. default = `target.byteLength`.",
"optional": true
},
{
"textRaw": "`sourceStart` {Integer} The offset within `buf` at which to begin comparison. Ignored when `targetStart` is `undefined`. default = `0` ",
"name": "sourceStart",
"type": "Integer",
"desc": "The offset within `buf` at which to begin comparison. Ignored when `targetStart` is `undefined`. default = `0`",
"optional": true
},
{
"textRaw": "`sourceEnd` {Integer} The offset within `buf` at which to end comparison. Ignored when `targetStart` is `undefined`. default = `buf.byteLength`. ",
"name": "sourceEnd",
"type": "Integer",
"desc": "The offset within `buf` at which to end comparison. Ignored when `targetStart` is `undefined`. default = `buf.byteLength`.",
"optional": true
}
]
},
{
"params": [
{
"name": "target"
},
{
"name": "targetStart",
"optional": true
},
{
"name": "targetEnd",
"optional": true
},
{
"name": "sourceStart",
"optional": true
},
{
"name": "sourceEnd",
"optional": true
}
]
}
],
"desc": "Compares two Buffer instances and returns a number indicating whether buf
\ncomes before, after, or is the same as the target
in sort order.\nComparison is based on the actual sequence of bytes in each Buffer.\n\n
0
is returned if target
is the same as buf
1
is returned if target
should come before buf
when sorted.-1
is returned if target
should come after buf
when sorted.const buf1 = Buffer.from('ABC');\nconst buf2 = Buffer.from('BCD');\nconst buf3 = Buffer.from('ABCD');\n\nconsole.log(buf1.compare(buf1));\n // Prints: 0\nconsole.log(buf1.compare(buf2));\n // Prints: -1\nconsole.log(buf1.compare(buf3));\n // Prints: 1\nconsole.log(buf2.compare(buf1));\n // Prints: 1\nconsole.log(buf2.compare(buf3));\n // Prints: 1\n\n[buf1, buf2, buf3].sort(Buffer.compare);\n // produces sort order [buf1, buf3, buf2]
\nThe optional targetStart
, targetEnd
, sourceStart
, and sourceEnd
\narguments can be used to limit the comparison to specific ranges within the two\nBuffer
objects.\n\n
const buf1 = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9]);\nconst buf2 = Buffer.from([5, 6, 7, 8, 9, 1, 2, 3, 4]);\n\nconsole.log(buf1.compare(buf2, 5, 9, 0, 4));\n // Prints: 0\nconsole.log(buf1.compare(buf2, 0, 6, 4));\n // Prints: -1\nconsole.log(buf1.compare(buf2, 5, 6, 5));\n // Prints: 1
\nA RangeError
will be thrown if: targetStart < 0
, sourceStart < 0
,\ntargetEnd > target.byteLength
or sourceEnd > source.byteLength
.\n\n
Copies data from a region of this Buffer to a region in the target Buffer even\nif the target memory region overlaps with the source.\n\n
\nExample: build two Buffers, then copy buf1
from byte 16 through byte 19\ninto buf2
, starting at the 8th byte in buf2
.\n\n
const buf1 = Buffer.allocUnsafe(26);\nconst buf2 = Buffer.allocUnsafe(26).fill('!');\n\nfor (let i = 0 ; i < 26 ; i++) {\n buf1[i] = i + 97; // 97 is ASCII a\n}\n\nbuf1.copy(buf2, 8, 16, 20);\nconsole.log(buf2.toString('ascii', 0, 25));\n // Prints: !!!!!!!!qrst!!!!!!!!!!!!!
\nExample: Build a single Buffer, then copy data from one region to an overlapping\nregion in the same Buffer\n\n
\nconst buf = Buffer.allocUnsafe(26);\n\nfor (var i = 0 ; i < 26 ; i++) {\n buf[i] = i + 97; // 97 is ASCII a\n}\n\nbuf.copy(buf, 0, 4, 10);\nconsole.log(buf.toString());\n\n// efghijghijklmnopqrstuvwxyz
\n"
},
{
"textRaw": "buf.entries()",
"type": "method",
"name": "entries",
"signatures": [
{
"return": {
"textRaw": "Return: {Iterator} ",
"name": "return",
"type": "Iterator"
},
"params": []
},
{
"params": []
}
],
"desc": "Creates and returns an [iterator][] of [index, byte]
pairs from the Buffer\ncontents.\n\n
const buf = Buffer.from('buffer');\nfor (var pair of buf.entries()) {\n console.log(pair);\n}\n// prints:\n// [0, 98]\n// [1, 117]\n// [2, 102]\n// [3, 102]\n// [4, 101]\n// [5, 114]
\n"
},
{
"textRaw": "buf.equals(otherBuffer)",
"type": "method",
"name": "equals",
"signatures": [
{
"return": {
"textRaw": "Return: {Boolean} ",
"name": "return",
"type": "Boolean"
},
"params": [
{
"textRaw": "`otherBuffer` {Buffer} ",
"name": "otherBuffer",
"type": "Buffer"
}
]
},
{
"params": [
{
"name": "otherBuffer"
}
]
}
],
"desc": "Returns a boolean indicating whether this
and otherBuffer
have exactly the\nsame bytes.\n\n
const buf1 = Buffer.from('ABC');\nconst buf2 = Buffer.from('414243', 'hex');\nconst buf3 = Buffer.from('ABCD');\n\nconsole.log(buf1.equals(buf2));\n // Prints: true\nconsole.log(buf1.equals(buf3));\n // Prints: false
\n"
},
{
"textRaw": "buf.fill(value[, offset[, end]][, encoding])",
"type": "method",
"name": "fill",
"signatures": [
{
"return": {
"textRaw": "Return: {Buffer} ",
"name": "return",
"type": "Buffer"
},
"params": [
{
"textRaw": "`value` {String|Buffer|Number} ",
"name": "value",
"type": "String|Buffer|Number"
},
{
"textRaw": "`offset` {Number} Default: 0 ",
"name": "offset",
"type": "Number",
"desc": "Default: 0",
"optional": true
},
{
"textRaw": "`end` {Number} Default: `buf.length` ",
"name": "end",
"type": "Number",
"desc": "Default: `buf.length`",
"optional": true
},
{
"textRaw": "`encoding` {String} Default: `'utf8'` ",
"name": "encoding",
"type": "String",
"desc": "Default: `'utf8'`",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset",
"optional": true
},
{
"name": "end",
"optional": true
},
{
"name": "encoding",
"optional": true
}
]
}
],
"desc": "Fills the Buffer with the specified value. If the offset
(defaults to 0
)\nand end
(defaults to buf.length
) are not given the entire buffer will be\nfilled. The method returns a reference to the Buffer, so calls can be chained.\nThis is meant as a small simplification to creating a Buffer. Allowing the\ncreation and fill of the Buffer to be done on a single line:\n\n
const b = Buffer.allocUnsafe(50).fill('h');\nconsole.log(b.toString());\n // Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh
\nencoding
is only relevant if value
is a string. Otherwise it is ignored.\nvalue
is coerced to a uint32
value if it is not a String or Number.\n\n
The fill()
operation writes bytes into the Buffer dumbly. If the final write\nfalls in between a multi-byte character then whatever bytes fit into the buffer\nare written.\n\n
Buffer(3).fill('\\u0222');\n // Prints: <Buffer c8 a2 c8>
\n"
},
{
"textRaw": "buf.indexOf(value[, byteOffset][, encoding])",
"type": "method",
"name": "indexOf",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`value` {String|Buffer|Number} ",
"name": "value",
"type": "String|Buffer|Number"
},
{
"textRaw": "`byteOffset` {Number} Default: 0 ",
"name": "byteOffset",
"type": "Number",
"desc": "Default: 0",
"optional": true
},
{
"textRaw": "`encoding` {String} Default: `'utf8'` ",
"name": "encoding",
"type": "String",
"desc": "Default: `'utf8'`",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "byteOffset",
"optional": true
},
{
"name": "encoding",
"optional": true
}
]
}
],
"desc": "Operates similar to [Array#indexOf()
][] in that it returns either the\nstarting index position of value
in Buffer or -1
if the Buffer does not\ncontain value
. The value
can be a String, Buffer or Number. Strings are by\ndefault interpreted as UTF8. Buffers will use the entire Buffer (to compare a\npartial Buffer use [buf.slice()
][]). Numbers can range from 0 to 255.\n\n
const buf = Buffer.from('this is a buffer');\n\nbuf.indexOf('this');\n // returns 0\nbuf.indexOf('is');\n // returns 2\nbuf.indexOf(Buffer.from('a buffer'));\n // returns 8\nbuf.indexOf(97); // ascii for 'a'\n // returns 8\nbuf.indexOf(Buffer.from('a buffer example'));\n // returns -1\nbuf.indexOf(Buffer.from('a buffer example').slice(0,8));\n // returns 8\n\nconst utf16Buffer = Buffer.from('\\u039a\\u0391\\u03a3\\u03a3\\u0395', 'ucs2');\n\nutf16Buffer.indexOf('\\u03a3', 0, 'ucs2');\n // returns 4\nutf16Buffer.indexOf('\\u03a3', -4, 'ucs2');\n // returns 6
\n"
},
{
"textRaw": "buf.includes(value[, byteOffset][, encoding])",
"type": "method",
"name": "includes",
"signatures": [
{
"return": {
"textRaw": "Return: {Boolean} ",
"name": "return",
"type": "Boolean"
},
"params": [
{
"textRaw": "`value` {String|Buffer|Number} ",
"name": "value",
"type": "String|Buffer|Number"
},
{
"textRaw": "`byteOffset` {Number} Default: 0 ",
"name": "byteOffset",
"type": "Number",
"desc": "Default: 0",
"optional": true
},
{
"textRaw": "`encoding` {String} Default: `'utf8'` ",
"name": "encoding",
"type": "String",
"desc": "Default: `'utf8'`",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "byteOffset",
"optional": true
},
{
"name": "encoding",
"optional": true
}
]
}
],
"desc": "Operates similar to [Array#includes()
][]. The value
can be a String, Buffer\nor Number. Strings are interpreted as UTF8 unless overridden with the\nencoding
argument. Buffers will use the entire Buffer (to compare a partial\nBuffer use [buf.slice()
][]). Numbers can range from 0 to 255.\n\n
The byteOffset
indicates the index in buf
where searching begins.\n\n
const buf = Buffer.from('this is a buffer');\n\nbuf.includes('this');\n // returns true\nbuf.includes('is');\n // returns true\nbuf.includes(Buffer.from('a buffer'));\n // returns true\nbuf.includes(97); // ascii for 'a'\n // returns true\nbuf.includes(Buffer.from('a buffer example'));\n // returns false\nbuf.includes(Buffer.from('a buffer example').slice(0,8));\n // returns true\nbuf.includes('this', 4);\n // returns false
\n"
},
{
"textRaw": "buf.keys()",
"type": "method",
"name": "keys",
"signatures": [
{
"return": {
"textRaw": "Return: {Iterator} ",
"name": "return",
"type": "Iterator"
},
"params": []
},
{
"params": []
}
],
"desc": "Creates and returns an [iterator][] of Buffer keys (indices).\n\n
\nconst buf = Buffer.from('buffer');\nfor (var key of buf.keys()) {\n console.log(key);\n}\n// prints:\n// 0\n// 1\n// 2\n// 3\n// 4\n// 5
\n"
},
{
"textRaw": "buf.lastIndexOf(value[, byteOffset][, encoding])",
"type": "method",
"name": "lastIndexOf",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`value` {String|Buffer|Number} ",
"name": "value",
"type": "String|Buffer|Number"
},
{
"textRaw": "`byteOffset` {Number} Default: `buf.length` ",
"name": "byteOffset",
"type": "Number",
"desc": "Default: `buf.length`",
"optional": true
},
{
"textRaw": "`encoding` {String} Default: `'utf8'` ",
"name": "encoding",
"type": "String",
"desc": "Default: `'utf8'`",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "byteOffset",
"optional": true
},
{
"name": "encoding",
"optional": true
}
]
}
],
"desc": "Identical to [Buffer#indexOf()
][], but searches the Buffer from back to front\ninstead of front to back. Returns the starting index position of value
in\nBuffer or -1
if the Buffer does not contain value
. The value
can be a\nString, Buffer or Number. Strings are by default interpreted as UTF8. If\nbyteOffset
is provided, will return the last match that begins at or before\nbyteOffset
.\n\n
const buf = new Buffer('this buffer is a buffer');\n\nbuf.lastIndexOf('this');\n // returns 0\nbuf.lastIndexOf('buffer');\n // returns 17\nbuf.lastIndexOf(new Buffer('buffer'));\n // returns 17\nbuf.lastIndexOf(97); // ascii for 'a'\n // returns 15\nbuf.lastIndexOf(new Buffer('yolo'));\n // returns -1\nbuf.lastIndexOf('buffer', 5)\n // returns 5\nbuf.lastIndexOf('buffer', 4)\n // returns -1\n\nconst utf16Buffer = new Buffer('\\u039a\\u0391\\u03a3\\u03a3\\u0395', 'ucs2');\n\nutf16Buffer.lastIndexOf('\\u03a3', null, 'ucs2');\n // returns 6\nutf16Buffer.lastIndexOf('\\u03a3', -5, 'ucs2');\n // returns 4
\n"
},
{
"textRaw": "buf.readDoubleBE(offset[, noAssert])",
"type": "method",
"name": "readDoubleBE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 8` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 8`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads a 64-bit double from the Buffer at the specified offset
with specified\nendian format (readDoubleBE()
returns big endian, readDoubleLE()
returns\nlittle endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
const buf = Buffer.from([1,2,3,4,5,6,7,8]);\n\nbuf.readDoubleBE();\n // Returns: 8.20788039913184e-304\nbuf.readDoubleLE();\n // Returns: 5.447603722011605e-270\nbuf.readDoubleLE(1);\n // throws RangeError: Index out of range\n\nbuf.readDoubleLE(1, true); // Warning: reads passed end of buffer!\n // Segmentation fault! don't do this!
\n"
},
{
"textRaw": "buf.readDoubleLE(offset[, noAssert])",
"type": "method",
"name": "readDoubleLE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 8` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 8`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads a 64-bit double from the Buffer at the specified offset
with specified\nendian format (readDoubleBE()
returns big endian, readDoubleLE()
returns\nlittle endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
const buf = Buffer.from([1,2,3,4,5,6,7,8]);\n\nbuf.readDoubleBE();\n // Returns: 8.20788039913184e-304\nbuf.readDoubleLE();\n // Returns: 5.447603722011605e-270\nbuf.readDoubleLE(1);\n // throws RangeError: Index out of range\n\nbuf.readDoubleLE(1, true); // Warning: reads passed end of buffer!\n // Segmentation fault! don't do this!
\n"
},
{
"textRaw": "buf.readFloatBE(offset[, noAssert])",
"type": "method",
"name": "readFloatBE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads a 32-bit float from the Buffer at the specified offset
with specified\nendian format (readFloatBE()
returns big endian, readFloatLE()
returns\nlittle endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
const buf = Buffer.from([1,2,3,4]);\n\nbuf.readFloatBE();\n // Returns: 2.387939260590663e-38\nbuf.readFloatLE();\n // Returns: 1.539989614439558e-36\nbuf.readFloatLE(1);\n // throws RangeError: Index out of range\n\nbuf.readFloatLE(1, true); // Warning: reads passed end of buffer!\n // Segmentation fault! don't do this!
\n"
},
{
"textRaw": "buf.readFloatLE(offset[, noAssert])",
"type": "method",
"name": "readFloatLE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads a 32-bit float from the Buffer at the specified offset
with specified\nendian format (readFloatBE()
returns big endian, readFloatLE()
returns\nlittle endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
const buf = Buffer.from([1,2,3,4]);\n\nbuf.readFloatBE();\n // Returns: 2.387939260590663e-38\nbuf.readFloatLE();\n // Returns: 1.539989614439558e-36\nbuf.readFloatLE(1);\n // throws RangeError: Index out of range\n\nbuf.readFloatLE(1, true); // Warning: reads passed end of buffer!\n // Segmentation fault! don't do this!
\n"
},
{
"textRaw": "buf.readInt8(offset[, noAssert])",
"type": "method",
"name": "readInt8",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 1` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 1`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads a signed 8-bit integer from the Buffer at the specified offset
.\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Integers read from the Buffer are interpreted as two's complement signed values.\n\n
\nconst buf = Buffer.from([1,-2,3,4]);\n\nbuf.readInt8(0);\n // returns 1\nbuf.readInt8(1);\n // returns -2
\n"
},
{
"textRaw": "buf.readInt16BE(offset[, noAssert])",
"type": "method",
"name": "readInt16BE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 2` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 2`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads a signed 16-bit integer from the Buffer at the specified offset
with\nthe specified endian format (readInt16BE()
returns big endian,\nreadInt16LE()
returns little endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Integers read from the Buffer are interpreted as two's complement signed values.\n\n
\nconst buf = Buffer.from([1,-2,3,4]);\n\nbuf.readInt16BE();\n // returns 510\nbuf.readInt16LE(1);\n // returns 1022
\n"
},
{
"textRaw": "buf.readInt16LE(offset[, noAssert])",
"type": "method",
"name": "readInt16LE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 2` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 2`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads a signed 16-bit integer from the Buffer at the specified offset
with\nthe specified endian format (readInt16BE()
returns big endian,\nreadInt16LE()
returns little endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Integers read from the Buffer are interpreted as two's complement signed values.\n\n
\nconst buf = Buffer.from([1,-2,3,4]);\n\nbuf.readInt16BE();\n // returns 510\nbuf.readInt16LE(1);\n // returns 1022
\n"
},
{
"textRaw": "buf.readInt32BE(offset[, noAssert])",
"type": "method",
"name": "readInt32BE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads a signed 32-bit integer from the Buffer at the specified offset
with\nthe specified endian format (readInt32BE()
returns big endian,\nreadInt32LE()
returns little endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Integers read from the Buffer are interpreted as two's complement signed values.\n\n
\nconst buf = Buffer.from([1,-2,3,4]);\n\nbuf.readInt32BE();\n // returns 33424132\nbuf.readInt32LE();\n // returns 67370497\nbuf.readInt32LE(1);\n // throws RangeError: Index out of range
\n"
},
{
"textRaw": "buf.readInt32LE(offset[, noAssert])",
"type": "method",
"name": "readInt32LE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads a signed 32-bit integer from the Buffer at the specified offset
with\nthe specified endian format (readInt32BE()
returns big endian,\nreadInt32LE()
returns little endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Integers read from the Buffer are interpreted as two's complement signed values.\n\n
\nconst buf = Buffer.from([1,-2,3,4]);\n\nbuf.readInt32BE();\n // returns 33424132\nbuf.readInt32LE();\n // returns 67370497\nbuf.readInt32LE(1);\n // throws RangeError: Index out of range
\n"
},
{
"textRaw": "buf.readIntBE(offset, byteLength[, noAssert])",
"type": "method",
"name": "readIntBE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - byteLength` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - byteLength`"
},
{
"textRaw": "`byteLength` {Number} `0 < byteLength <= 6` ",
"name": "byteLength",
"type": "Number",
"desc": "`0 < byteLength <= 6`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "byteLength"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "byteLength"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads byteLength
number of bytes from the Buffer at the specified offset
\nand interprets the result as a two's complement signed value. Supports up to 48\nbits of accuracy. For example:\n\n
const buf = Buffer.allocUnsafe(6);\nbuf.writeUInt16LE(0x90ab, 0);\nbuf.writeUInt32LE(0x12345678, 2);\nbuf.readIntLE(0, 6).toString(16); // Specify 6 bytes (48 bits)\n// Returns: '1234567890ab'\n\nbuf.readIntBE(0, 6).toString(16);\n// Returns: -546f87a9cbee
\nSetting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Reads byteLength
number of bytes from the Buffer at the specified offset
\nand interprets the result as a two's complement signed value. Supports up to 48\nbits of accuracy. For example:\n\n
const buf = Buffer.allocUnsafe(6);\nbuf.writeUInt16LE(0x90ab, 0);\nbuf.writeUInt32LE(0x12345678, 2);\nbuf.readIntLE(0, 6).toString(16); // Specify 6 bytes (48 bits)\n// Returns: '1234567890ab'\n\nbuf.readIntBE(0, 6).toString(16);\n// Returns: -546f87a9cbee
\nSetting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Reads an unsigned 8-bit integer from the Buffer at the specified offset
.\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
const buf = Buffer.from([1,-2,3,4]);\n\nbuf.readUInt8(0);\n // returns 1\nbuf.readUInt8(1);\n // returns 254
\n"
},
{
"textRaw": "buf.readUInt16BE(offset[, noAssert])",
"type": "method",
"name": "readUInt16BE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 2` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 2`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads an unsigned 16-bit integer from the Buffer at the specified offset
with\nspecified endian format (readUInt16BE()
returns big endian,\nreadUInt16LE()
returns little endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Example:\n\n
\nconst buf = Buffer.from([0x3, 0x4, 0x23, 0x42]);\n\nbuf.readUInt16BE(0);\n // Returns: 0x0304\nbuf.readUInt16LE(0);\n // Returns: 0x0403\nbuf.readUInt16BE(1);\n // Returns: 0x0423\nbuf.readUInt16LE(1);\n // Returns: 0x2304\nbuf.readUInt16BE(2);\n // Returns: 0x2342\nbuf.readUInt16LE(2);\n // Returns: 0x4223
\n"
},
{
"textRaw": "buf.readUInt16LE(offset[, noAssert])",
"type": "method",
"name": "readUInt16LE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 2` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 2`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads an unsigned 16-bit integer from the Buffer at the specified offset
with\nspecified endian format (readUInt16BE()
returns big endian,\nreadUInt16LE()
returns little endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Example:\n\n
\nconst buf = Buffer.from([0x3, 0x4, 0x23, 0x42]);\n\nbuf.readUInt16BE(0);\n // Returns: 0x0304\nbuf.readUInt16LE(0);\n // Returns: 0x0403\nbuf.readUInt16BE(1);\n // Returns: 0x0423\nbuf.readUInt16LE(1);\n // Returns: 0x2304\nbuf.readUInt16BE(2);\n // Returns: 0x2342\nbuf.readUInt16LE(2);\n // Returns: 0x4223
\n"
},
{
"textRaw": "buf.readUInt32BE(offset[, noAssert])",
"type": "method",
"name": "readUInt32BE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads an unsigned 32-bit integer from the Buffer at the specified offset
with\nspecified endian format (readUInt32BE()
returns big endian,\nreadUInt32LE()
returns little endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Example:\n\n
\nconst buf = Buffer.from([0x3, 0x4, 0x23, 0x42]);\n\nbuf.readUInt32BE(0);\n // Returns: 0x03042342\nconsole.log(buf.readUInt32LE(0));\n // Returns: 0x42230403
\n"
},
{
"textRaw": "buf.readUInt32LE(offset[, noAssert])",
"type": "method",
"name": "readUInt32LE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads an unsigned 32-bit integer from the Buffer at the specified offset
with\nspecified endian format (readUInt32BE()
returns big endian,\nreadUInt32LE()
returns little endian).\n\n
Setting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Example:\n\n
\nconst buf = Buffer.from([0x3, 0x4, 0x23, 0x42]);\n\nbuf.readUInt32BE(0);\n // Returns: 0x03042342\nconsole.log(buf.readUInt32LE(0));\n // Returns: 0x42230403
\n"
},
{
"textRaw": "buf.readUIntBE(offset, byteLength[, noAssert])",
"type": "method",
"name": "readUIntBE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} ",
"name": "return",
"type": "Number"
},
"params": [
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - byteLength` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - byteLength`"
},
{
"textRaw": "`byteLength` {Number} `0 < byteLength <= 6` ",
"name": "byteLength",
"type": "Number",
"desc": "`0 < byteLength <= 6`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "byteLength"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "offset"
},
{
"name": "byteLength"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Reads byteLength
number of bytes from the Buffer at the specified offset
\nand interprets the result as an unsigned integer. Supports up to 48\nbits of accuracy. For example:\n\n
const buf = Buffer.allocUnsafe(6);\nbuf.writeUInt16LE(0x90ab, 0);\nbuf.writeUInt32LE(0x12345678, 2);\nbuf.readUIntLE(0, 6).toString(16); // Specify 6 bytes (48 bits)\n// Returns: '1234567890ab'\n\nbuf.readUIntBE(0, 6).toString(16);\n// Returns: ab9078563412
\nSetting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Reads byteLength
number of bytes from the Buffer at the specified offset
\nand interprets the result as an unsigned integer. Supports up to 48\nbits of accuracy. For example:\n\n
const buf = Buffer.allocUnsafe(6);\nbuf.writeUInt16LE(0x90ab, 0);\nbuf.writeUInt32LE(0x12345678, 2);\nbuf.readUIntLE(0, 6).toString(16); // Specify 6 bytes (48 bits)\n// Returns: '1234567890ab'\n\nbuf.readUIntBE(0, 6).toString(16);\n// Returns: ab9078563412
\nSetting noAssert
to true
skips validation of the offset
. This allows the\noffset
to be beyond the end of the Buffer.\n\n
Returns a new Buffer that references the same memory as the original, but\noffset and cropped by the start
and end
indices.\n\n
Note that modifying the new Buffer slice will modify the memory in the\noriginal Buffer because the allocated memory of the two objects overlap.\n\n
\nExample: build a Buffer with the ASCII alphabet, take a slice, then modify one\nbyte from the original Buffer.\n\n
\nconst buf1 = Buffer.allocUnsafe(26);\n\nfor (var i = 0 ; i < 26 ; i++) {\n buf1[i] = i + 97; // 97 is ASCII a\n}\n\nconst buf2 = buf1.slice(0, 3);\nbuf2.toString('ascii', 0, buf2.length);\n // Returns: 'abc'\nbuf1[0] = 33;\nbuf2.toString('ascii', 0, buf2.length);\n // Returns : '!bc'
\nSpecifying negative indexes causes the slice to be generated relative to the\nend of the Buffer rather than the beginning.\n\n
\nconst buf = Buffer.from('buffer');\n\nbuf.slice(-6, -1).toString();\n // Returns 'buffe', equivalent to buf.slice(0, 5)\nbuf.slice(-6, -2).toString();\n // Returns 'buff', equivalent to buf.slice(0, 4)\nbuf.slice(-5, -2).toString();\n // Returns 'uff', equivalent to buf.slice(1, 4)
\n"
},
{
"textRaw": "buf.swap16()",
"type": "method",
"name": "swap16",
"signatures": [
{
"return": {
"textRaw": "Return: {Buffer} ",
"name": "return",
"type": "Buffer"
},
"params": []
},
{
"params": []
}
],
"desc": "Interprets the Buffer
as an array of unsigned 16-bit integers and swaps\nthe byte-order in-place. Throws a RangeError
if the Buffer
length is\nnot a multiple of 16 bits. The method returns a reference to the Buffer, so\ncalls can be chained.\n\n
const buf = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);\nconsole.log(buf);\n // Prints Buffer(0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8)\nbuf.swap16();\nconsole.log(buf);\n // Prints Buffer(0x2, 0x1, 0x4, 0x3, 0x6, 0x5, 0x8, 0x7)
\n"
},
{
"textRaw": "buf.swap32()",
"type": "method",
"name": "swap32",
"signatures": [
{
"return": {
"textRaw": "Return: {Buffer} ",
"name": "return",
"type": "Buffer"
},
"params": []
},
{
"params": []
}
],
"desc": "Interprets the Buffer
as an array of unsigned 32-bit integers and swaps\nthe byte-order in-place. Throws a RangeError
if the Buffer
length is\nnot a multiple of 32 bits. The method returns a reference to the Buffer, so\ncalls can be chained.\n\n
const buf = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);\nconsole.log(buf);\n // Prints Buffer(0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8)\nbuf.swap32();\nconsole.log(buf);\n // Prints Buffer(0x4, 0x3, 0x2, 0x1, 0x8, 0x7, 0x6, 0x5)
\n"
},
{
"textRaw": "buf.toString([encoding[, start[, end]]])",
"type": "method",
"name": "toString",
"signatures": [
{
"return": {
"textRaw": "Return: {String} ",
"name": "return",
"type": "String"
},
"params": [
{
"textRaw": "`encoding` {String} Default: `'utf8'` ",
"name": "encoding",
"type": "String",
"desc": "Default: `'utf8'`",
"optional": true
},
{
"textRaw": "`start` {Number} Default: 0 ",
"name": "start",
"type": "Number",
"desc": "Default: 0",
"optional": true
},
{
"textRaw": "`end` {Number} Default: `buffer.length` ",
"name": "end",
"type": "Number",
"desc": "Default: `buffer.length`",
"optional": true
}
]
},
{
"params": [
{
"name": "encoding",
"optional": true
},
{
"name": "start",
"optional": true
},
{
"name": "end",
"optional": true
}
]
}
],
"desc": "Decodes and returns a string from the Buffer data using the specified\ncharacter set encoding
.\n\n
const buf = Buffer.allocUnsafe(26);\nfor (var i = 0 ; i < 26 ; i++) {\n buf[i] = i + 97; // 97 is ASCII a\n}\nbuf.toString('ascii');\n // Returns: 'abcdefghijklmnopqrstuvwxyz'\nbuf.toString('ascii',0,5);\n // Returns: 'abcde'\nbuf.toString('utf8',0,5);\n // Returns: 'abcde'\nbuf.toString(undefined,0,5);\n // Returns: 'abcde', encoding defaults to 'utf8'
\n"
},
{
"textRaw": "buf.toJSON()",
"type": "method",
"name": "toJSON",
"signatures": [
{
"return": {
"textRaw": "Return: {Object} ",
"name": "return",
"type": "Object"
},
"params": []
},
{
"params": []
}
],
"desc": "Returns a JSON representation of the Buffer instance. [JSON.stringify()
][]\nimplicitly calls this function when stringifying a Buffer instance.\n\n
Example:\n\n
\nconst buf = Buffer.from('test');\nconst json = JSON.stringify(buf);\n\nconsole.log(json);\n// Prints: '{"type":"Buffer","data":[116,101,115,116]}'\n\nconst copy = JSON.parse(json, (key, value) => {\n return value && value.type === 'Buffer'\n ? Buffer.from(value.data)\n : value;\n });\n\nconsole.log(copy.toString());\n// Prints: 'test'
\n"
},
{
"textRaw": "buf.values()",
"type": "method",
"name": "values",
"signatures": [
{
"return": {
"textRaw": "Return: {Iterator} ",
"name": "return",
"type": "Iterator"
},
"params": []
},
{
"params": []
}
],
"desc": "Creates and returns an [iterator][] for Buffer values (bytes). This function is\ncalled automatically when the Buffer is used in a for..of
statement.\n\n
const buf = Buffer.from('buffer');\nfor (var value of buf.values()) {\n console.log(value);\n}\n// prints:\n// 98\n// 117\n// 102\n// 102\n// 101\n// 114\n\nfor (var value of buf) {\n console.log(value);\n}\n// prints:\n// 98\n// 117\n// 102\n// 102\n// 101\n// 114
\n"
},
{
"textRaw": "buf.write(string[, offset[, length]][, encoding])",
"type": "method",
"name": "write",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} Numbers of bytes written ",
"name": "return",
"type": "Number",
"desc": "Numbers of bytes written"
},
"params": [
{
"textRaw": "`string` {String} Bytes to be written to buffer ",
"name": "string",
"type": "String",
"desc": "Bytes to be written to buffer"
},
{
"textRaw": "`offset` {Number} Default: 0 ",
"name": "offset",
"type": "Number",
"desc": "Default: 0",
"optional": true
},
{
"textRaw": "`length` {Number} Default: `buffer.length - offset` ",
"name": "length",
"type": "Number",
"desc": "Default: `buffer.length - offset`",
"optional": true
},
{
"textRaw": "`encoding` {String} Default: `'utf8'` ",
"name": "encoding",
"type": "String",
"desc": "Default: `'utf8'`",
"optional": true
}
]
},
{
"params": [
{
"name": "string"
},
{
"name": "offset",
"optional": true
},
{
"name": "length",
"optional": true
},
{
"name": "encoding",
"optional": true
}
]
}
],
"desc": "Writes string
to the Buffer at offset
using the given encoding
.\nThe length
parameter is the number of bytes to write. If the Buffer did not\ncontain enough space to fit the entire string, only a partial amount of the\nstring will be written however, it will not write only partially encoded\ncharacters.\n\n
const buf = Buffer.allocUnsafe(256);\nconst len = buf.write('\\u00bd + \\u00bc = \\u00be', 0);\nconsole.log(`${len} bytes: ${buf.toString('utf8', 0, len)}`);\n // Prints: 12 bytes: ½ + ¼ = ¾
\n"
},
{
"textRaw": "buf.writeDoubleBE(value, offset[, noAssert])",
"type": "method",
"name": "writeDoubleBE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 8` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 8`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeDoubleBE()
writes big endian, writeDoubleLE()
writes little\nendian). The value
argument should be a valid 64-bit double. Behavior is\nnot defined when value
is anything other than a 64-bit double.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Example:\n\n
\nconst buf = Buffer.allocUnsafe(8);\nbuf.writeDoubleBE(0xdeadbeefcafebabe, 0);\n\nconsole.log(buf);\n // Prints: <Buffer 43 eb d5 b7 dd f9 5f d7>\n\nbuf.writeDoubleLE(0xdeadbeefcafebabe, 0);\n\nconsole.log(buf);\n // Prints: <Buffer d7 5f f9 dd b7 d5 eb 43>
\n"
},
{
"textRaw": "buf.writeDoubleLE(value, offset[, noAssert])",
"type": "method",
"name": "writeDoubleLE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 8` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 8`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeDoubleBE()
writes big endian, writeDoubleLE()
writes little\nendian). The value
argument should be a valid 64-bit double. Behavior is\nnot defined when value
is anything other than a 64-bit double.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Example:\n\n
\nconst buf = Buffer.allocUnsafe(8);\nbuf.writeDoubleBE(0xdeadbeefcafebabe, 0);\n\nconsole.log(buf);\n // Prints: <Buffer 43 eb d5 b7 dd f9 5f d7>\n\nbuf.writeDoubleLE(0xdeadbeefcafebabe, 0);\n\nconsole.log(buf);\n // Prints: <Buffer d7 5f f9 dd b7 d5 eb 43>
\n"
},
{
"textRaw": "buf.writeFloatBE(value, offset[, noAssert])",
"type": "method",
"name": "writeFloatBE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeFloatBE()
writes big endian, writeFloatLE()
writes little\nendian). Behavior is not defined when value
is anything other than a 32-bit\nfloat.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Example:\n\n
\nconst buf = Buffer.allocUnsafe(4);\nbuf.writeFloatBE(0xcafebabe, 0);\n\nconsole.log(buf);\n // Prints: <Buffer 4f 4a fe bb>\n\nbuf.writeFloatLE(0xcafebabe, 0);\n\nconsole.log(buf);\n // Prints: <Buffer bb fe 4a 4f>
\n"
},
{
"textRaw": "buf.writeFloatLE(value, offset[, noAssert])",
"type": "method",
"name": "writeFloatLE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeFloatBE()
writes big endian, writeFloatLE()
writes little\nendian). Behavior is not defined when value
is anything other than a 32-bit\nfloat.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Example:\n\n
\nconst buf = Buffer.allocUnsafe(4);\nbuf.writeFloatBE(0xcafebabe, 0);\n\nconsole.log(buf);\n // Prints: <Buffer 4f 4a fe bb>\n\nbuf.writeFloatLE(0xcafebabe, 0);\n\nconsole.log(buf);\n // Prints: <Buffer bb fe 4a 4f>
\n"
},
{
"textRaw": "buf.writeInt8(value, offset[, noAssert])",
"type": "method",
"name": "writeInt8",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 1` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 1`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
. The value
should be a\nvalid signed 8-bit integer. Behavior is not defined when value
is anything\nother than a signed 8-bit integer.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
The value
is interpreted and written as a two's complement signed integer.\n\n
const buf = Buffer.allocUnsafe(2);\nbuf.writeInt8(2, 0);\nbuf.writeInt8(-2, 1);\nconsole.log(buf);\n // Prints: <Buffer 02 fe>
\n"
},
{
"textRaw": "buf.writeInt16BE(value, offset[, noAssert])",
"type": "method",
"name": "writeInt16BE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 2` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 2`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeInt16BE()
writes big endian, writeInt16LE()
writes little\nendian). The value
should be a valid signed 16-bit integer. Behavior is\nnot defined when value
is anything other than a signed 16-bit integer.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
The value
is interpreted and written as a two's complement signed integer.\n\n
const buf = Buffer.allocUnsafe(4);\nbuf.writeInt16BE(0x0102,0);\nbuf.writeInt16LE(0x0304,2);\nconsole.log(buf);\n // Prints: <Buffer 01 02 04 03>
\n"
},
{
"textRaw": "buf.writeInt16LE(value, offset[, noAssert])",
"type": "method",
"name": "writeInt16LE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 2` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 2`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeInt16BE()
writes big endian, writeInt16LE()
writes little\nendian). The value
should be a valid signed 16-bit integer. Behavior is\nnot defined when value
is anything other than a signed 16-bit integer.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
The value
is interpreted and written as a two's complement signed integer.\n\n
const buf = Buffer.allocUnsafe(4);\nbuf.writeInt16BE(0x0102,0);\nbuf.writeInt16LE(0x0304,2);\nconsole.log(buf);\n // Prints: <Buffer 01 02 04 03>
\n"
},
{
"textRaw": "buf.writeInt32BE(value, offset[, noAssert])",
"type": "method",
"name": "writeInt32BE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeInt32BE()
writes big endian, writeInt32LE()
writes little\nendian). The value
should be a valid signed 32-bit integer. Behavior is\nnot defined when value
is anything other than a signed 32-bit integer.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
The value
is interpreted and written as a two's complement signed integer.\n\n
const buf = Buffer.allocUnsafe(8);\nbuf.writeInt32BE(0x01020304,0);\nbuf.writeInt32LE(0x05060708,4);\nconsole.log(buf);\n // Prints: <Buffer 01 02 03 04 08 07 06 05>
\n"
},
{
"textRaw": "buf.writeInt32LE(value, offset[, noAssert])",
"type": "method",
"name": "writeInt32LE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeInt32BE()
writes big endian, writeInt32LE()
writes little\nendian). The value
should be a valid signed 32-bit integer. Behavior is\nnot defined when value
is anything other than a signed 32-bit integer.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
The value
is interpreted and written as a two's complement signed integer.\n\n
const buf = Buffer.allocUnsafe(8);\nbuf.writeInt32BE(0x01020304,0);\nbuf.writeInt32LE(0x05060708,4);\nconsole.log(buf);\n // Prints: <Buffer 01 02 03 04 08 07 06 05>
\n"
},
{
"textRaw": "buf.writeIntBE(value, offset, byteLength[, noAssert])",
"type": "method",
"name": "writeIntBE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - byteLength` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - byteLength`"
},
{
"textRaw": "`byteLength` {Number} `0 < byteLength <= 6` ",
"name": "byteLength",
"type": "Number",
"desc": "`0 < byteLength <= 6`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "byteLength"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "byteLength"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
and byteLength
.\nSupports up to 48 bits of accuracy. For example:\n\n
const buf1 = Buffer.allocUnsafe(6);\nbuf1.writeUIntBE(0x1234567890ab, 0, 6);\nconsole.log(buf1);\n // Prints: <Buffer 12 34 56 78 90 ab>\n\nconst buf2 = Buffer.allocUnsafe(6);\nbuf2.writeUIntLE(0x1234567890ab, 0, 6);\nconsole.log(buf2);\n // Prints: <Buffer ab 90 78 56 34 12>
\nSet noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Behavior is not defined when value
is anything other than an integer.\n\n
Writes value
to the Buffer at the specified offset
and byteLength
.\nSupports up to 48 bits of accuracy. For example:\n\n
const buf1 = Buffer.allocUnsafe(6);\nbuf1.writeUIntBE(0x1234567890ab, 0, 6);\nconsole.log(buf1);\n // Prints: <Buffer 12 34 56 78 90 ab>\n\nconst buf2 = Buffer.allocUnsafe(6);\nbuf2.writeUIntLE(0x1234567890ab, 0, 6);\nconsole.log(buf2);\n // Prints: <Buffer ab 90 78 56 34 12>
\nSet noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Behavior is not defined when value
is anything other than an integer.\n\n
Writes value
to the Buffer at the specified offset
. The value
should be a\nvalid unsigned 8-bit integer. Behavior is not defined when value
is anything\nother than an unsigned 8-bit integer.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Example:\n\n
\nconst buf = Buffer.allocUnsafe(4);\nbuf.writeUInt8(0x3, 0);\nbuf.writeUInt8(0x4, 1);\nbuf.writeUInt8(0x23, 2);\nbuf.writeUInt8(0x42, 3);\n\nconsole.log(buf);\n // Prints: <Buffer 03 04 23 42>
\n"
},
{
"textRaw": "buf.writeUInt16BE(value, offset[, noAssert])",
"type": "method",
"name": "writeUInt16BE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 2` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 2`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeUInt16BE()
writes big endian, writeUInt16LE()
writes little\nendian). The value
should be a valid unsigned 16-bit integer. Behavior is\nnot defined when value
is anything other than an unsigned 16-bit integer.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Example:\n\n
\nconst buf = Buffer.allocUnsafe(4);\nbuf.writeUInt16BE(0xdead, 0);\nbuf.writeUInt16BE(0xbeef, 2);\n\nconsole.log(buf);\n // Prints: <Buffer de ad be ef>\n\nbuf.writeUInt16LE(0xdead, 0);\nbuf.writeUInt16LE(0xbeef, 2);\n\nconsole.log(buf);\n // Prints: <Buffer ad de ef be>
\n"
},
{
"textRaw": "buf.writeUInt16LE(value, offset[, noAssert])",
"type": "method",
"name": "writeUInt16LE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 2` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 2`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeUInt16BE()
writes big endian, writeUInt16LE()
writes little\nendian). The value
should be a valid unsigned 16-bit integer. Behavior is\nnot defined when value
is anything other than an unsigned 16-bit integer.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Example:\n\n
\nconst buf = Buffer.allocUnsafe(4);\nbuf.writeUInt16BE(0xdead, 0);\nbuf.writeUInt16BE(0xbeef, 2);\n\nconsole.log(buf);\n // Prints: <Buffer de ad be ef>\n\nbuf.writeUInt16LE(0xdead, 0);\nbuf.writeUInt16LE(0xbeef, 2);\n\nconsole.log(buf);\n // Prints: <Buffer ad de ef be>
\n"
},
{
"textRaw": "buf.writeUInt32BE(value, offset[, noAssert])",
"type": "method",
"name": "writeUInt32BE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeUInt32BE()
writes big endian, writeUInt32LE()
writes little\nendian). The value
should be a valid unsigned 32-bit integer. Behavior is\nnot defined when value
is anything other than an unsigned 32-bit integer.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Example:\n\n
\nconst buf = Buffer.allocUnsafe(4);\nbuf.writeUInt32BE(0xfeedface, 0);\n\nconsole.log(buf);\n // Prints: <Buffer fe ed fa ce>\n\nbuf.writeUInt32LE(0xfeedface, 0);\n\nconsole.log(buf);\n // Prints: <Buffer ce fa ed fe>
\n"
},
{
"textRaw": "buf.writeUInt32LE(value, offset[, noAssert])",
"type": "method",
"name": "writeUInt32LE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - 4` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - 4`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
with specified endian\nformat (writeUInt32BE()
writes big endian, writeUInt32LE()
writes little\nendian). The value
should be a valid unsigned 32-bit integer. Behavior is\nnot defined when value
is anything other than an unsigned 32-bit integer.\n\n
Set noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Example:\n\n
\nconst buf = Buffer.allocUnsafe(4);\nbuf.writeUInt32BE(0xfeedface, 0);\n\nconsole.log(buf);\n // Prints: <Buffer fe ed fa ce>\n\nbuf.writeUInt32LE(0xfeedface, 0);\n\nconsole.log(buf);\n // Prints: <Buffer ce fa ed fe>
\n"
},
{
"textRaw": "buf.writeUIntBE(value, offset, byteLength[, noAssert])",
"type": "method",
"name": "writeUIntBE",
"signatures": [
{
"return": {
"textRaw": "Return: {Number} The offset plus the number of written bytes ",
"name": "return",
"type": "Number",
"desc": "The offset plus the number of written bytes"
},
"params": [
{
"textRaw": "`value` {Number} Bytes to be written to Buffer ",
"name": "value",
"type": "Number",
"desc": "Bytes to be written to Buffer"
},
{
"textRaw": "`offset` {Number} `0 <= offset <= buf.length - byteLength` ",
"name": "offset",
"type": "Number",
"desc": "`0 <= offset <= buf.length - byteLength`"
},
{
"textRaw": "`byteLength` {Number} `0 < byteLength <= 6` ",
"name": "byteLength",
"type": "Number",
"desc": "`0 < byteLength <= 6`"
},
{
"textRaw": "`noAssert` {Boolean} Default: false ",
"name": "noAssert",
"type": "Boolean",
"desc": "Default: false",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "byteLength"
},
{
"name": "noAssert",
"optional": true
}
]
},
{
"params": [
{
"name": "value"
},
{
"name": "offset"
},
{
"name": "byteLength"
},
{
"name": "noAssert",
"optional": true
}
]
}
],
"desc": "Writes value
to the Buffer at the specified offset
and byteLength
.\nSupports up to 48 bits of accuracy. For example:\n\n
const buf = Buffer.allocUnsafe(6);\nbuf.writeUIntBE(0x1234567890ab, 0, 6);\nconsole.log(buf);\n // Prints: <Buffer 12 34 56 78 90 ab>
\nSet noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Behavior is not defined when value
is anything other than an unsigned integer.\n\n
Writes value
to the Buffer at the specified offset
and byteLength
.\nSupports up to 48 bits of accuracy. For example:\n\n
const buf = Buffer.allocUnsafe(6);\nbuf.writeUIntBE(0x1234567890ab, 0, 6);\nconsole.log(buf);\n // Prints: <Buffer 12 34 56 78 90 ab>
\nSet noAssert
to true to skip validation of value
and offset
. This means\nthat value
may be too large for the specific function and offset
may be\nbeyond the end of the Buffer leading to the values being silently dropped. This\nshould not be used unless you are certain of correctness.\n\n
Behavior is not defined when value
is anything other than an unsigned integer.\n\n
Stability: 0 - Deprecated: Use [`Buffer.from(array)`][buffer_from_array]\ninstead.
\narray
{Array}Allocates a new Buffer using an array
of octets.\n\n
const buf = new Buffer([0x62,0x75,0x66,0x66,0x65,0x72]);\n // creates a new Buffer containing ASCII bytes\n // ['b','u','f','f','e','r']
\n"
},
{
"params": [
{
"name": "buffer"
}
],
"desc": "Stability: 0 - Deprecated: Use [`Buffer.from(buffer)`][buffer_from_buffer]\ninstead.
\nbuffer
{Buffer}Copies the passed buffer
data onto a new Buffer
instance.\n\n
const buf1 = new Buffer('buffer');\nconst buf2 = new Buffer(buf1);\n\nbuf1[0] = 0x61;\nconsole.log(buf1.toString());\n // 'auffer'\nconsole.log(buf2.toString());\n // 'buffer' (copy is not changed)
\n"
},
{
"params": [
{
"name": "arrayBuffer"
},
{
"name": "byteOffset",
"optional": true
},
{
"name": "length",
"optional": true
}
],
"desc": "Stability: 0 - Deprecated: Use\n[`Buffer.from(arrayBuffer[, byteOffset [, length]])`][buffer_from_arraybuf]\ninstead.
\narrayBuffer
{ArrayBuffer} The .buffer
property of a TypedArray
or a\nnew ArrayBuffer()
byteOffset
{Number} Default: 0
length
{Number} Default: arrayBuffer.length - byteOffset
When passed a reference to the .buffer
property of a TypedArray
instance,\nthe newly created Buffer will share the same allocated memory as the\nTypedArray.\n\n
The optional byteOffset
and length
arguments specify a memory range within\nthe arrayBuffer
that will be shared by the Buffer
.\n\n
const arr = new Uint16Array(2);\narr[0] = 5000;\narr[1] = 4000;\n\nconst buf = new Buffer(arr.buffer); // shares the memory with arr;\n\nconsole.log(buf);\n // Prints: <Buffer 88 13 a0 0f>\n\n// changing the TypdArray changes the Buffer also\narr[1] = 6000;\n\nconsole.log(buf);\n // Prints: <Buffer 88 13 70 17>
\n"
},
{
"params": [
{
"name": "size"
}
],
"desc": "Stability: 0 - Deprecated: Use\n[`Buffer.alloc(size[, fill[, encoding]])`][buffer_alloc] instead (also\nsee [`Buffer.allocUnsafe(size)`][buffer_allocunsafe]).
\nsize
{Number}Allocates a new Buffer
of size
bytes. The size
must be less than\nor equal to the value of require('buffer').kMaxLength
(on 64-bit\narchitectures, kMaxLength
is (2^31)-1
). Otherwise, a [RangeError
][] is\nthrown. A zero-length Buffer will be created if a size
less than or equal to\n0 is specified.\n\n
Unlike ArrayBuffers
, the underlying memory for Buffer
instances created in\nthis way is not initialized. The contents of a newly created Buffer
are\nunknown and could contain sensitive data. Use [buf.fill(0)
][] to initialize\na Buffer
to zeroes.\n\n
const buf = new Buffer(5);\nconsole.log(buf);\n // <Buffer 78 e0 82 02 01>\n // (octets will be different, every time)\nbuf.fill(0);\nconsole.log(buf);\n // <Buffer 00 00 00 00 00>
\n"
},
{
"params": [
{
"name": "str"
},
{
"name": "encoding",
"optional": true
}
],
"desc": "Stability: 0 - Deprecated:\nUse [`Buffer.from(str[, encoding])`][buffer_from_string] instead.
\nstr
{String} string to encode.encoding
{String} Default: 'utf8'
Creates a new Buffer containing the given JavaScript string str
. If\nprovided, the encoding
parameter identifies the strings character encoding.\n\n
const buf1 = new Buffer('this is a tést');\nconsole.log(buf1.toString());\n // prints: this is a tést\nconsole.log(buf1.toString('ascii'));\n // prints: this is a tC)st\n\nconst buf2 = new Buffer('7468697320697320612074c3a97374', 'hex');\nconsole.log(buf2.toString());\n // prints: this is a tést
\n"
}
]
},
{
"textRaw": "Class: SlowBuffer",
"type": "class",
"name": "SlowBuffer",
"desc": "Stability: 0 - Deprecated: Use\n[`Buffer.allocUnsafeSlow(size)`][buffer_allocunsafeslow] instead.
\nReturns an un-pooled Buffer
.\n\n
In order to avoid the garbage collection overhead of creating many individually\nallocated Buffers, by default allocations under 4KB are sliced from a single\nlarger allocated object. This approach improves both performance and memory\nusage since v8 does not need to track and cleanup as many Persistent
objects.\n\n
In the case where a developer may need to retain a small chunk of memory from a\npool for an indeterminate amount of time, it may be appropriate to create an\nun-pooled Buffer instance using SlowBuffer
then copy out the relevant bits.\n\n
// need to keep around a few small chunks of memory\nconst store = [];\n\nsocket.on('readable', () => {\n var data = socket.read();\n // allocate for retained data\n var sb = SlowBuffer(10);\n // copy the data into the new allocation\n data.copy(sb, 0, 0, 10);\n store.push(sb);\n});
\nUse of SlowBuffer
should be used only as a last resort after a developer\nhas observed undue memory retention in their applications.\n\n
Stability: 0 - Deprecated: Use\n[`Buffer.allocUnsafeSlow(size)`][buffer_allocunsafeslow] instead.
\nsize
NumberAllocates a new SlowBuffer
of size
bytes. The size
must be less than\nor equal to the value of require('buffer').kMaxLength
(on 64-bit\narchitectures, kMaxLength
is (2^31)-1
). Otherwise, a [RangeError
][] is\nthrown. A zero-length Buffer will be created if a size
less than or equal to\n0 is specified.\n\n
The underlying memory for SlowBuffer
instances is not initialized. The\ncontents of a newly created SlowBuffer
are unknown and could contain\nsensitive data. Use [buf.fill(0)
][] to initialize a SlowBuffer
to zeroes.\n\n
const SlowBuffer = require('buffer').SlowBuffer;\nconst buf = new SlowBuffer(5);\nconsole.log(buf);\n // <Buffer 78 e0 82 02 01>\n // (octets will be different, every time)\nbuf.fill(0);\nconsole.log(buf);\n // <Buffer 00 00 00 00 00>
\n"
}
]
}
],
"properties": [
{
"textRaw": "`INSPECT_MAX_BYTES` {Number} Default: 50 ",
"type": "Number",
"name": "INSPECT_MAX_BYTES",
"desc": "Returns the maximum number of bytes that will be returned when\nbuffer.inspect()
is called. This can be overridden by user modules. See\n[util.inspect()
][] for more details on buffer.inspect()
behavior.\n\n
Note that this is a property on the buffer
module as returned by\nrequire('buffer')
, not on the Buffer global or a Buffer instance.\n\n
The child_process
module provides the ability to spawn child processes in\na manner that is similar, but not identical, to popen(3). This capability\nis primarily provided by the [child_process.spawn()
][] function:\n\n
const spawn = require('child_process').spawn;\nconst ls = spawn('ls', ['-lh', '/usr']);\n\nls.stdout.on('data', (data) => {\n console.log(`stdout: ${data}`);\n});\n\nls.stderr.on('data', (data) => {\n console.log(`stderr: ${data}`);\n});\n\nls.on('close', (code) => {\n console.log(`child process exited with code ${code}`);\n});
\nBy default, pipes for stdin
, stdout
and stderr
are established between\nthe parent Node.js process and the spawned child. It is possible to stream data\nthrough these pipes in a non-blocking way. Note, however, that some programs\nuse line-buffered I/O internally. While that does not affect Node.js, it can\nmean that data sent to the child process may not be immediately consumed.\n\n
The [child_process.spawn()
][] method spawns the child process asynchronously,\nwithout blocking the Node.js event loop. The [child_process.spawnSync()
][]\nfunction provides equivalent functionality in a synchronous manner that blocks\nthe event loop until the spawned process either exits or is terminated.\n\n
For convenience, the child_process
module provides a handful of synchronous\nand asynchronous alternatives to [child_process.spawn()
][] and\n[child_process.spawnSync()
][]. Note that each of these alternatives are\nimplemented on top of [child_process.spawn()
][] or [child_process.spawnSync()
][].\n\n
child_process.exec()
][]: spawns a shell and runs a command within that shell,\npassing the stdout
and stderr
to a callback function when complete.child_process.execFile()
][]: similar to [child_process.exec()
][] except that\nit spawns the command directly without first spawning a shell.child_process.fork()
][]: spawns a new Node.js process and invokes a\nspecified module with an IPC communication channel established that allows\nsending messages between parent and child.child_process.execSync()
][]: a synchronous version of\n[child_process.exec()
][] that will block the Node.js event loop.child_process.execFileSync()
][]: a synchronous version of\n[child_process.execFile()
][] that will block the Node.js event loop.For certain use cases, such as automating shell scripts, the\n[synchronous counterparts][] may be more convenient. In many cases, however,\nthe synchronous methods can have significant impact on performance due to\nstalling the event loop while spawned processes complete.\n\n
\n", "modules": [ { "textRaw": "Asynchronous Process Creation", "name": "asynchronous_process_creation", "desc": "The [child_process.spawn()
][], [child_process.fork()
][], [child_process.exec()
][],\nand [child_process.execFile()
][] methods all follow the idiomatic asynchronous\nprogramming pattern typical of other Node.js APIs.\n\n
Each of the methods returns a [ChildProcess
][] instance. These objects\nimplement the Node.js [EventEmitter
][] API, allowing the parent process to\nregister listener functions that are called when certain events occur during\nthe life cycle of the child process.\n\n
The [child_process.exec()
][] and [child_process.execFile()
][] methods additionally\nallow for an optional callback
function to be specified that is invoked\nwhen the child process terminates.\n\n
The importance of the distinction between [child_process.exec()
][] and\n[child_process.execFile()
][] can vary based on platform. On Unix-type operating\nsystems (Unix, Linux, OSX) [child_process.execFile()
][] can be more efficient\nbecause it does not spawn a shell. On Windows, however, .bat
and .cmd
\nfiles are not executable on their own without a terminal, and therefore cannot\nbe launched using [child_process.execFile()
][]. When running on Windows, .bat
\nand .cmd
files can be invoked using [child_process.spawn()
][] with the shell
\noption set, with [child_process.exec()
][], or by spawning cmd.exe
and passing\nthe .bat
or .cmd
file as an argument (which is what the shell
option and\n[child_process.exec()
][] do).\n\n
// On Windows Only ...\nconst spawn = require('child_process').spawn;\nconst bat = spawn('cmd.exe', ['/c', 'my.bat']);\n\nbat.stdout.on('data', (data) => {\n console.log(data);\n});\n\nbat.stderr.on('data', (data) => {\n console.log(data);\n});\n\nbat.on('exit', (code) => {\n console.log(`Child exited with code ${code}`);\n});\n\n// OR...\nconst exec = require('child_process').exec;\nexec('my.bat', (err, stdout, stderr) => {\n if (err) {\n console.error(err);\n return;\n }\n console.log(stdout);\n});
\n",
"type": "module",
"displayName": "Spawning `.bat` and `.cmd` files on Windows"
}
],
"methods": [
{
"textRaw": "child_process.exec(command[, options][, callback])",
"type": "method",
"name": "exec",
"signatures": [
{
"return": {
"textRaw": "Return: {ChildProcess} ",
"name": "return",
"type": "ChildProcess"
},
"params": [
{
"textRaw": "`command` {String} The command to run, with space-separated arguments ",
"name": "command",
"type": "String",
"desc": "The command to run, with space-separated arguments"
},
{
"textRaw": "`options` {Object} ",
"options": [
{
"textRaw": "`cwd` {String} Current working directory of the child process ",
"name": "cwd",
"type": "String",
"desc": "Current working directory of the child process"
},
{
"textRaw": "`env` {Object} Environment key-value pairs ",
"name": "env",
"type": "Object",
"desc": "Environment key-value pairs"
},
{
"textRaw": "`encoding` {String} (Default: `'utf8'`) ",
"name": "encoding",
"type": "String",
"desc": "(Default: `'utf8'`)"
},
{
"textRaw": "`shell` {String} Shell to execute the command with (Default: `'/bin/sh'` on UNIX, `'cmd.exe'` on Windows, The shell should understand the `-c` switch on UNIX or `/s /c` on Windows. On Windows, command line parsing should be compatible with `cmd.exe`.) ",
"name": "shell",
"type": "String",
"desc": "Shell to execute the command with (Default: `'/bin/sh'` on UNIX, `'cmd.exe'` on Windows, The shell should understand the `-c` switch on UNIX or `/s /c` on Windows. On Windows, command line parsing should be compatible with `cmd.exe`.)"
},
{
"textRaw": "`timeout` {Number} (Default: `0`) ",
"name": "timeout",
"default": "0",
"type": "Number"
},
{
"textRaw": "[`maxBuffer`][] {Number} largest amount of data (in bytes) allowed on stdout or stderr - if exceeded child process is killed (Default: `200\\*1024`) ",
"name": "[",
"default": "200\\*1024",
"desc": "maxBuffer`][] {Number} largest amount of data (in bytes) allowed on stdout or stderr - if exceeded child process is killed"
},
{
"textRaw": "`killSignal` {String} (Default: `'SIGTERM'`) ",
"name": "killSignal",
"type": "String",
"desc": "(Default: `'SIGTERM'`)"
},
{
"textRaw": "`uid` {Number} Sets the user identity of the process. (See setuid(2).) ",
"name": "uid",
"type": "Number",
"desc": "Sets the user identity of the process. (See setuid(2).)"
},
{
"textRaw": "`gid` {Number} Sets the group identity of the process. (See setgid(2).) ",
"name": "gid",
"type": "Number",
"desc": "Sets the group identity of the process. (See setgid(2).)"
}
],
"name": "options",
"type": "Object",
"optional": true
},
{
"textRaw": "`callback` {Function} called with the output when process terminates ",
"options": [
{
"textRaw": "`error` {Error} ",
"name": "error",
"type": "Error"
},
{
"textRaw": "`stdout` {String|Buffer} ",
"name": "stdout",
"type": "String|Buffer"
},
{
"textRaw": "`stderr` {String|Buffer} ",
"name": "stderr",
"type": "String|Buffer"
}
],
"name": "callback",
"type": "Function",
"desc": "called with the output when process terminates",
"optional": true
}
]
},
{
"params": [
{
"name": "command"
},
{
"name": "options",
"optional": true
},
{
"name": "callback",
"optional": true
}
]
}
],
"desc": "Spawns a shell then executes the command
within that shell, buffering any\ngenerated output.\n\n
const exec = require('child_process').exec;\nconst child = exec('cat *.js bad_file | wc -l',\n (error, stdout, stderr) => {\n console.log(`stdout: ${stdout}`);\n console.log(`stderr: ${stderr}`);\n if (error !== null) {\n console.log(`exec error: ${error}`);\n }\n});
\nIf a callback
function is provided, it is called with the arguments\n(error, stdout, stderr)
. On success, error
will be null
. On error,\nerror
will be an instance of [Error
][]. The error.code
property will be\nthe exit code of the child process while error.signal
will be set to the\nsignal that terminated the process. Any exit code other than 0
is considered\nto be an error.\n\n
The stdout
and stderr
arguments passed to the callback will contain the\nstdout and stderr output of the child process. By default, Node.js will decode\nthe output as UTF-8 and pass strings to the callback. The encoding
option\ncan be used to specify the character encoding used to decode the stdout and\nstderr output. If encoding
is 'buffer'
, Buffer
objects will be passed to\nthe callback instead.\n\n
The options
argument may be passed as the second argument to customize how\nthe process is spawned. The default options are:\n\n
{\n encoding: 'utf8',\n timeout: 0,\n maxBuffer: 200*1024,\n killSignal: 'SIGTERM',\n cwd: null,\n env: null\n}
\nIf timeout
is greater than 0
, the parent will send the the signal\nidentified by the killSignal
property (the default is 'SIGTERM'
) if the\nchild runs longer than timeout
milliseconds.\n\n
Note: Unlike the exec(3) POSIX system call, child_process.exec()
does not\nreplace the existing process and uses a shell to execute the command.\n\n
The child_process.execFile()
function is similar to [child_process.exec()
][]\nexcept that it does not spawn a shell. Rather, the specified executable file
\nis spawned directly as a new process making it slightly more efficient than\n[child_process.exec()
][].\n\n
The same options as [child_process.exec()
][] are supported. Since a shell is not\nspawned, behaviors such as I/O redirection and file globbing are not supported.\n\n
const execFile = require('child_process').execFile;\nconst child = execFile('node', ['--version'], (error, stdout, stderr) => {\n if (error) {\n throw error;\n }\n console.log(stdout);\n});
\nThe stdout
and stderr
arguments passed to the callback will contain the\nstdout and stderr output of the child process. By default, Node.js will decode\nthe output as UTF-8 and pass strings to the callback. The encoding
option\ncan be used to specify the character encoding used to decode the stdout and\nstderr output. If encoding
is 'buffer'
, Buffer
objects will be passed to\nthe callback instead.\n\n
The child_process.fork()
method is a special case of\n[child_process.spawn()
][] used specifically to spawn new Node.js processes.\nLike [child_process.spawn()
][], a [ChildProcess
][] object is returned. The returned\n[ChildProcess
][] will have an additional communication channel built-in that\nallows messages to be passed back and forth between the parent and child. See\n[child.send()
][] for details.\n\n
It is important to keep in mind that spawned Node.js child processes are\nindependent of the parent with exception of the IPC communication channel\nthat is established between the two. Each process has it's own memory, with\ntheir own V8 instances. Because of the additional resource allocations\nrequired, spawning a large number of child Node.js processes is not\nrecommended.\n\n
\nBy default, child_process.fork()
will spawn new Node.js instances using the\n[process.execPath
][] of the parent process. The execPath
property in the\noptions
object allows for an alternative execution path to be used.\n\n
Node.js processes launched with a custom execPath
will communicate with the\nparent process using the file descriptor (fd) identified using the\nenvironment variable NODE_CHANNEL_FD
on the child process. The input and\noutput on this fd is expected to be line delimited JSON objects.\n\n
Note: Unlike the fork(2) POSIX system call, child_process.fork()
does\nnot clone the current process.\n\n
The child_process.spawn()
method spawns a new process using the given\ncommand
, with command line arguments in args
. If omitted, args
defaults\nto an empty array.\n\n
A third argument may be used to specify additional options, with these defaults:\n\n
\n{\n cwd: undefined,\n env: process.env\n}
\nUse cwd
to specify the working directory from which the process is spawned.\nIf not given, the default is to inherit the current working directory.\n\n
Use env
to specify environment variables that will be visible to the new\nprocess, the default is [process.env
][].\n\n
Example of running ls -lh /usr
, capturing stdout
, stderr
, and the\nexit code:\n\n
const spawn = require('child_process').spawn;\nconst ls = spawn('ls', ['-lh', '/usr']);\n\nls.stdout.on('data', (data) => {\n console.log(`stdout: ${data}`);\n});\n\nls.stderr.on('data', (data) => {\n console.log(`stderr: ${data}`);\n});\n\nls.on('close', (code) => {\n console.log(`child process exited with code ${code}`);\n});
\nExample: A very elaborate way to run ps ax | grep ssh
\n\n
const spawn = require('child_process').spawn;\nconst ps = spawn('ps', ['ax']);\nconst grep = spawn('grep', ['ssh']);\n\nps.stdout.on('data', (data) => {\n grep.stdin.write(data);\n});\n\nps.stderr.on('data', (data) => {\n console.log(`ps stderr: ${data}`);\n});\n\nps.on('close', (code) => {\n if (code !== 0) {\n console.log(`ps process exited with code ${code}`);\n }\n grep.stdin.end();\n});\n\ngrep.stdout.on('data', (data) => {\n console.log(`${data}`);\n});\n\ngrep.stderr.on('data', (data) => {\n console.log(`grep stderr: ${data}`);\n});\n\ngrep.on('close', (code) => {\n if (code !== 0) {\n console.log(`grep process exited with code ${code}`);\n }\n});
\nExample of checking for failed exec:\n\n
\nconst spawn = require('child_process').spawn;\nconst child = spawn('bad_command');\n\nchild.on('error', (err) => {\n console.log('Failed to start child process.');\n});
\n",
"properties": [
{
"textRaw": "options.detached",
"name": "detached",
"desc": "On Windows, setting options.detached
to true
makes it possible for the\nchild process to continue running after the parent exits. The child will have\nits own console window. Once enabled for a child process, it cannot be\ndisabled.\n\n
On non-Windows platforms, if options.detached
is set to true
, the child\nprocess will be made the leader of a new process group and session. Note that\nchild processes may continue running after the parent exits regardless of\nwhether they are detached or not. See setsid(2) for more information.\n\n
By default, the parent will wait for the detached child to exit. To prevent\nthe parent from waiting for a given child
, use the child.unref()
method.\nDoing so will cause the parent's event loop to not include the child in its\nreference count, allowing the parent to exit independently of the child, unless\nthere is an established IPC channel between the child and parent.\n\n
When using the detached
option to start a long-running process, the process\nwill not stay running in the background after the parent exits unless it is\nprovided with a stdio
configuration that is not connected to the parent.\nIf the parent's stdio
is inherited, the child will remain attached to the\ncontrolling terminal.\n\n
Example of a long-running process, by detaching and also ignoring its parent\nstdio
file descriptors, in order to ignore the parent's termination:\n\n
const spawn = require('child_process').spawn;\n\nconst child = spawn(process.argv[0], ['child_program.js'], {\n detached: true,\n stdio: ['ignore']\n});\n\nchild.unref();
\nAlternatively one can redirect the child process' output into files:\n\n
\nconst fs = require('fs');\nconst spawn = require('child_process').spawn;\nconst out = fs.openSync('./out.log', 'a');\nconst err = fs.openSync('./out.log', 'a');\n\nconst child = spawn('prg', [], {\n detached: true,\n stdio: [ 'ignore', out, err ]\n});\n\nchild.unref();
\n"
},
{
"textRaw": "options.stdio",
"name": "stdio",
"desc": "The options.stdio
option is used to configure the pipes that are established\nbetween the parent and child process. By default, the child's stdin, stdout,\nand stderr are redirected to corresponding [child.stdin
][], [child.stdout
][], and\n[child.stderr
][] streams on the [ChildProcess
][] object. This is equivalent to\nsetting the options.stdio
equal to ['pipe', 'pipe', 'pipe']
.\n\n
For convenience, options.stdio
may be one of the following strings:\n\n
'pipe'
- equivalent to ['pipe', 'pipe', 'pipe']
(the default)'ignore'
- equivalent to ['ignore', 'ignore', 'ignore']
'inherit'
- equivalent to [process.stdin, process.stdout, process.stderr]
\n or [0,1,2]
Otherwise, the value of options.stdio
is an array where each index corresponds\nto an fd in the child. The fds 0, 1, and 2 correspond to stdin, stdout,\nand stderr, respectively. Additional fds can be specified to create additional\npipes between the parent and child. The value is one of the following:\n\n
'pipe'
- Create a pipe between the child process and the parent process.\nThe parent end of the pipe is exposed to the parent as a property on the\nchild_process
object as [child.stdio[fd]
][stdio
]. Pipes created for\nfds 0 - 2 are also available as [child.stdin
][], [child.stdout
][]\nand [child.stderr
][], respectively.'ipc'
- Create an IPC channel for passing messages/file descriptors\nbetween parent and child. A [ChildProcess
][] may have at most one IPC stdio\nfile descriptor. Setting this option enables the [child.send()
][] method.\nIf the child writes JSON messages to this file descriptor, the\n[child.on('message')
]['message'
] event handler will be triggered in the parent.\nIf the child is a Node.js process, the presence of an IPC channel will enable\n[process.send()
][], [process.disconnect()
][], [process.on('disconnect')
][], and\n[process.on('message')
] within the child.'ignore'
- Instructs Node.js to ignore the fd in the child. While Node.js\nwill always open fds 0 - 2 for the processes it spawns, setting the fd to\n'ignore'
will cause Node.js to open /dev/null
and attach it to the\nchild's fd.stdio
array. Note that the stream must\nhave an underlying descriptor (file streams do not until the 'open'
\nevent has occurred).null
, undefined
- Use default value. For stdio fds 0, 1 and 2 (in other\nwords, stdin, stdout, and stderr) a pipe is created. For fd 3 and up, the\ndefault is 'ignore'
.Example:\n\n
\nconst spawn = require('child_process').spawn;\n\n// Child will use parent's stdios\nspawn('prg', [], { stdio: 'inherit' });\n\n// Spawn child sharing only stderr\nspawn('prg', [], { stdio: ['pipe', 'pipe', process.stderr] });\n\n// Open an extra fd=4, to interact with programs presenting a\n// startd-style interface.\nspawn('prg', [], { stdio: ['pipe', null, null, null, 'pipe'] });
\nIt is worth noting that when an IPC channel is established between the\nparent and child processes, and the child is a Node.js process, the child\nis launched with the IPC channel unreferenced (using unref()
) until the\nchild registers an event handler for the [process.on('disconnect')
][] event.\nThis allows the child to exit normally without the process being held open\nby the open IPC channel.\n\n
See also: [child_process.exec()
][] and [child_process.fork()
][]\n\n
The [child_process.spawnSync()
][], [child_process.execSync()
][], and\n[child_process.execFileSync()
][] methods are synchronous and WILL block\nthe Node.js event loop, pausing execution of any additional code until the\nspawned process exits.\n\n
Blocking calls like these are mostly useful for simplifying general purpose\nscripting tasks and for simplifying the loading/processing of application\nconfiguration at startup.\n\n
\n", "methods": [ { "textRaw": "child_process.execFileSync(file[, args][, options])", "type": "method", "name": "execFileSync", "signatures": [ { "return": { "textRaw": "return: {Buffer|String} The stdout from the command ", "name": "return", "type": "Buffer|String", "desc": "The stdout from the command" }, "params": [ { "textRaw": "`file` {String} The name or path of the executable file to run ", "name": "file", "type": "String", "desc": "The name or path of the executable file to run" }, { "textRaw": "`args` {Array} List of string arguments ", "name": "args", "type": "Array", "desc": "List of string arguments", "optional": true }, { "textRaw": "`options` {Object} ", "options": [ { "textRaw": "`cwd` {String} Current working directory of the child process ", "name": "cwd", "type": "String", "desc": "Current working directory of the child process" }, { "textRaw": "`input` {String|Buffer} The value which will be passed as stdin to the spawned process ", "options": [ { "textRaw": "supplying this value will override `stdio[0]` ", "name": "supplying", "desc": "this value will override `stdio[0]`" } ], "name": "input", "type": "String|Buffer", "desc": "The value which will be passed as stdin to the spawned process" }, { "textRaw": "`stdio` {Array} Child's stdio configuration. (Default: `'pipe'`) ", "options": [ { "textRaw": "`stderr` by default will be output to the parent process' stderr unless `stdio` is specified ", "name": "stderr", "desc": "by default will be output to the parent process' stderr unless `stdio` is specified" } ], "name": "stdio", "type": "Array", "desc": "Child's stdio configuration. (Default: `'pipe'`)" }, { "textRaw": "`env` {Object} Environment key-value pairs ", "name": "env", "type": "Object", "desc": "Environment key-value pairs" }, { "textRaw": "`uid` {Number} Sets the user identity of the process. (See setuid(2).) ", "name": "uid", "type": "Number", "desc": "Sets the user identity of the process. (See setuid(2).)" }, { "textRaw": "`gid` {Number} Sets the group identity of the process. (See setgid(2).) ", "name": "gid", "type": "Number", "desc": "Sets the group identity of the process. (See setgid(2).)" }, { "textRaw": "`timeout` {Number} In milliseconds the maximum amount of time the process is allowed to run. (Default: `undefined`) ", "name": "timeout", "default": "undefined", "type": "Number", "desc": "In milliseconds the maximum amount of time the process is allowed to run." }, { "textRaw": "`killSignal` {String} The signal value to be used when the spawned process will be killed. (Default: `'SIGTERM'`) ", "name": "killSignal", "type": "String", "desc": "The signal value to be used when the spawned process will be killed. (Default: `'SIGTERM'`)" }, { "textRaw": "[`maxBuffer`][] {Number} largest amount of data (in bytes) allowed on stdout or stderr - if exceeded child process is killed ", "name": "[", "desc": "maxBuffer`][] {Number} largest amount of data (in bytes) allowed on stdout or stderr - if exceeded child process is killed" }, { "textRaw": "`encoding` {String} The encoding used for all stdio inputs and outputs. (Default: `'buffer'`) ", "name": "encoding", "type": "String", "desc": "The encoding used for all stdio inputs and outputs. (Default: `'buffer'`)" } ], "name": "options", "type": "Object", "optional": true } ] }, { "params": [ { "name": "file" }, { "name": "args", "optional": true }, { "name": "options", "optional": true } ] } ], "desc": "The child_process.execFileSync()
method is generally identical to\n[child_process.execFile()
][] with the exception that the method will not return\nuntil the child process has fully closed. When a timeout has been encountered\nand killSignal
is sent, the method won't return until the process has\ncompletely exited. Note that if the child process intercepts and handles\nthe SIGTERM
signal and does not exit, the parent process will still wait\nuntil the child process has exited.\n\n
If the process times out, or has a non-zero exit code, this method will\nthrow. The [Error
][] object will contain the entire result from\n[child_process.spawnSync()
][]\n\n
The child_process.execSync()
method is generally identical to\n[child_process.exec()
][] with the exception that the method will not return until\nthe child process has fully closed. When a timeout has been encountered and\nkillSignal
is sent, the method won't return until the process has completely\nexited. Note that if the child process intercepts and handles the SIGTERM
\nsignal and doesn't exit, the parent process will wait until the child\nprocess has exited.\n\n
If the process times out, or has a non-zero exit code, this method will\nthrow. The [Error
][] object will contain the entire result from\n[child_process.spawnSync()
][]\n\n
The child_process.spawnSync()
method is generally identical to\n[child_process.spawn()
][] with the exception that the function will not return\nuntil the child process has fully closed. When a timeout has been encountered\nand killSignal
is sent, the method won't return until the process has\ncompletely exited. Note that if the process intercepts and handles the\nSIGTERM
signal and doesn't exit, the parent process will wait until the child\nprocess has exited.\n\n
It is important to keep in mind that the maxBuffer
option specifies the\nlargest number of octets allowed on stdout
or stderr
- if this value is\nexceeded then the child process is terminated. This particularly impacts\noutput that includes multi-byte character encodings such as UTF-8 or UTF-16.\nFor instance, the following will output 13 UTF-8 encoded octets to stdout
\nalthough there are only 4 characters:\n\n
console.log('中文测试');
\n",
"type": "module",
"displayName": "`maxBuffer` and Unicode"
}
],
"classes": [
{
"textRaw": "Class: ChildProcess",
"type": "class",
"name": "ChildProcess",
"desc": "Instances of the ChildProcess
class are [EventEmitters
][EventEmitter
] that represent\nspawned child processes.\n\n
Instances of ChildProcess
are not intended to be created directly. Rather,\nuse the [child_process.spawn()
][], [child_process.exec()
][],\n[child_process.execFile()
][], or [child_process.fork()
][] methods to create\ninstances of ChildProcess
.\n\n
The 'close'
event is emitted when the stdio streams of a child process have\nbeen closed. This is distinct from the ['exit'
][] event, since multiple\nprocesses might share the same stdio streams.\n\n
The 'disconnect'
event is emitted after calling the\n[child.disconnect()
][] method in parent process or [process.disconnect()
][] in child process. After\ndisconnecting it is no longer possible to send or receive messages, and the\n[child.connected
][] property is false
.\n\n
The 'error'
event is emitted whenever:\n\n
Note that the 'exit'
event may or may not fire after an error has occurred.\nIf you are listening to both the 'exit'
and 'error'
events, it is important\nto guard against accidentally invoking handler functions multiple times.\n\n
See also [child.kill()
][] and [child.send()
][].\n\n
The 'exit'
event is emitted after the child process ends. If the process\nexited, code
is the final exit code of the process, otherwise null
. If the\nprocess terminated due to receipt of a signal, signal
is the string name of\nthe signal, otherwise null
. One of the two will always be non-null.\n\n
Note that when the 'exit'
event is triggered, child process stdio streams\nmight still be open.\n\n
Also, note that Node.js establishes signal handlers for SIGINT
and\nSIGTERM
and Node.js processes will not terminate immediately due to receipt\nof those signals. Rather, Node.js will perform a sequence of cleanup actions\nand then will re-raise the handled signal.\n\n
See waitpid(2).\n\n
\n" }, { "textRaw": "Event: 'message'", "type": "event", "name": "message", "params": [], "desc": "The 'message'
event is triggered when a child process uses [process.send()
][]\nto send messages.\n\n
The child.connected
property indicates whether it is still possible to send\nand receive messages from a child process. When child.connected
is false
, it\nis no longer possible to send or receive messages.\n\n
Returns the process identifier (PID) of the child process.\n\n
\nExample:\n\n
\nconst spawn = require('child_process').spawn;\nconst grep = spawn('grep', ['ssh']);\n\nconsole.log(`Spawned child pid: ${grep.pid}`);\ngrep.stdin.end();
\n",
"shortDesc": "Integer"
},
{
"textRaw": "`stderr` {Stream} ",
"type": "Stream",
"name": "stderr",
"desc": "A Readable Stream
that represents the child process's stderr
.\n\n
If the child was spawned with stdio[2]
set to anything other than 'pipe'
,\nthen this will be undefined
.\n\n
child.stderr
is an alias for child.stdio[2]
. Both properties will refer to\nthe same value.\n\n
A Writable Stream
that represents the child process's stdin
.\n\n
Note that if a child process waits to read all of its input, the child will not\ncontinue until this stream has been closed via end()
.\n\n
If the child was spawned with stdio[0]
set to anything other than 'pipe'
,\nthen this will be undefined
.\n\n
child.stdin
is an alias for child.stdio[0]
. Both properties will refer to\nthe same value.\n\n
A sparse array of pipes to the child process, corresponding with positions in\nthe [stdio
][] option passed to [child_process.spawn()
][] that have been set\nto the value 'pipe'
. Note that child.stdio[0]
, child.stdio[1]
, and\nchild.stdio[2]
are also available as child.stdin
, child.stdout
, and\nchild.stderr
, respectively.\n\n
In the following example, only the child's fd 1
(stdout) is configured as a\npipe, so only the parent's child.stdio[1]
is a stream, all other values in\nthe array are null
.\n\n
const assert = require('assert');\nconst fs = require('fs');\nconst child_process = require('child_process');\n\nconst child = child_process.spawn('ls', {\n stdio: [\n 0, // Use parents stdin for child\n 'pipe', // Pipe child's stdout to parent\n fs.openSync('err.out', 'w') // Direct child's stderr to a file\n ]\n});\n\nassert.equal(child.stdio[0], null);\nassert.equal(child.stdio[0], child.stdin);\n\nassert(child.stdout);\nassert.equal(child.stdio[1], child.stdout);\n\nassert.equal(child.stdio[2], null);\nassert.equal(child.stdio[2], child.stderr);
\n"
},
{
"textRaw": "`stdout` {Stream} ",
"type": "Stream",
"name": "stdout",
"desc": "A Readable Stream
that represents the child process's stdout
.\n\n
If the child was spawned with stdio[1]
set to anything other than 'pipe'
,\nthen this will be undefined
.\n\n
child.stdout
is an alias for child.stdio[1]
. Both properties will refer\nto the same value.\n\n
Closes the IPC channel between parent and child, allowing the child to exit\ngracefully once there are no other connections keeping it alive. After calling\nthis method the child.connected
and process.connected
properties in both\nthe parent and child (respectively) will be set to false
, and it will be no\nlonger possible to pass messages between the processes.\n\n
The 'disconnect'
event will be emitted when there are no messages in the\nprocess of being received. This will most often be triggered immediately after\ncalling child.disconnect()
.\n\n
Note that when the child process is a Node.js instance (e.g. spawned using\n[child_process.fork()
]), the process.disconnect()
method can be invoked\nwithin the child process to close the IPC channel as well.\n\n
The child.kill()
methods sends a signal to the child process. If no argument\nis given, the process will be sent the 'SIGTERM'
signal. See signal(7)
for\na list of available signals.\n\n
const spawn = require('child_process').spawn;\nconst grep = spawn('grep', ['ssh']);\n\ngrep.on('close', (code, signal) => {\n console.log(\n `child process terminated due to receipt of signal ${signal}`);\n});\n\n// Send SIGHUP to process\ngrep.kill('SIGHUP');
\nThe [ChildProcess
][] object may emit an ['error'
][] event if the signal cannot be\ndelivered. Sending a signal to a child process that has already exited is not\nan error but may have unforeseen consequences. Specifically, if the process\nidentifier (PID) has been reassigned to another process, the signal will be\ndelivered to that process instead which can have unexpected results.\n\n
Note that while the function is called kill
, the signal delivered to the\nchild process may not actually terminate the process.\n\n
See kill(2) for reference.\n\n
\nAlso note: on Linux, child processes of child processes will not be terminated\nwhen attempting to kill their parent. This is likely to happen when running a\nnew process in a shell or with use of the shell
option of ChildProcess
, such\nas in this example:\n\n
'use strict';\nconst spawn = require('child_process').spawn;\n\nlet child = spawn('sh', ['-c',\n `node -e "setInterval(() => {\n console.log(process.pid + 'is alive')\n }, 500);"`\n ], {\n stdio: ['inherit', 'inherit', 'inherit']\n });\n\nsetTimeout(() => {\n child.kill(); // does not terminate the node process in the shell\n}, 2000);
\n"
},
{
"textRaw": "child.send(message[, sendHandle[, options]][, callback])",
"type": "method",
"name": "send",
"signatures": [
{
"return": {
"textRaw": "Return: {Boolean} ",
"name": "return",
"type": "Boolean"
},
"params": [
{
"textRaw": "`message` {Object} ",
"name": "message",
"type": "Object"
},
{
"textRaw": "`sendHandle` {Handle} ",
"name": "sendHandle",
"type": "Handle",
"optional": true
},
{
"textRaw": "`options` {Object} ",
"name": "options",
"type": "Object",
"optional": true
},
{
"textRaw": "`callback` {Function} ",
"name": "callback",
"type": "Function",
"optional": true
}
]
},
{
"params": [
{
"name": "message"
},
{
"name": "sendHandle",
"optional": true
},
{
"name": "options",
"optional": true
},
{
"name": "callback",
"optional": true
}
]
}
],
"desc": "When an IPC channel has been established between the parent and child (\ni.e. when using [child_process.fork()
][]), the child.send()
method can be\nused to send messages to the child process. When the child process is a Node.js\ninstance, these messages can be received via the [process.on('message')
][] event.\n\n
For example, in the parent script:\n\n
\nconst cp = require('child_process');\nconst n = cp.fork(`${__dirname}/sub.js`);\n\nn.on('message', (m) => {\n console.log('PARENT got message:', m);\n});\n\nn.send({ hello: 'world' });
\nAnd then the child script, 'sub.js'
might look like this:\n\n
process.on('message', (m) => {\n console.log('CHILD got message:', m);\n});\n\nprocess.send({ foo: 'bar' });
\nChild Node.js processes will have a [process.send()
][] method of their own that\nallows the child to send messages back to the parent.\n\n
There is a special case when sending a {cmd: 'NODE_foo'}
message. All messages\ncontaining a NODE_
prefix in its cmd
property are considered to be reserved\nfor use within Node.js core and will not be emitted in the child's\n[process.on('message')
][] event. Rather, such messages are emitted using the\nprocess.on('internalMessage')
event and are consumed internally by Node.js.\nApplications should avoid using such messages or listening for\n'internalMessage'
events as it is subject to change without notice.\n\n
The optional sendHandle
argument that may be passed to child.send()
is for\npassing a TCP server or socket object to the child process. The child will\nreceive the object as the second argument passed to the callback function\nregistered on the [process.on('message')
][] event.\n\n
The options
argument, if present, is an object used to parameterize the\nsending of certain types of handles. options
supports the following\nproperties:\n\n
keepOpen
- A Boolean value that can be used when passing instances of\nnet.Socket
. When true
, the socket is kept open in the sending process.\nDefaults to false
.The optional callback
is a function that is invoked after the message is\nsent but before the child may have received it. The function is called with a\nsingle argument: null
on success, or an [Error
][] object on failure.\n\n
If no callback
function is provided and the message cannot be sent, an\n'error'
event will be emitted by the [ChildProcess
][] object. This can happen,\nfor instance, when the child process has already exited.\n\n
child.send()
will return false
if the channel has closed or when the\nbacklog of unsent messages exceeds a threshold that makes it unwise to send\nmore. Otherwise, the method returns true
. The callback
function can be\nused to implement flow control.\n\n
The sendHandle
argument can be used, for instance, to pass the handle of\na TCP server object to the child process as illustrated in the example below:\n\n
const child = require('child_process').fork('child.js');\n\n// Open up the server object and send the handle.\nconst server = require('net').createServer();\nserver.on('connection', (socket) => {\n socket.end('handled by parent');\n});\nserver.listen(1337, () => {\n child.send('server', server);\n});
\nThe child would then receive the server object as:\n\n
\nprocess.on('message', (m, server) => {\n if (m === 'server') {\n server.on('connection', (socket) => {\n socket.end('handled by child');\n });\n }\n});
\nOnce the server is now shared between the parent and child, some connections\ncan be handled by the parent and some by the child.\n\n
\nWhile the example above uses a server created using the net
module, dgram
\nmodule servers use exactly the same workflow with the exceptions of listening on\na 'message'
event instead of 'connection'
and using server.bind()
instead of\nserver.listen()
. This is, however, currently only supported on UNIX platforms.\n\n
Similarly, the sendHandler
argument can be used to pass the handle of a\nsocket to the child process. The example below spawns two children that each\nhandle connections with "normal" or "special" priority:\n\n
const normal = require('child_process').fork('child.js', ['normal']);\nconst special = require('child_process').fork('child.js', ['special']);\n\n// Open up the server and send sockets to child\nconst server = require('net').createServer();\nserver.on('connection', (socket) => {\n\n // If this is special priority\n if (socket.remoteAddress === '74.125.127.100') {\n special.send('socket', socket);\n return;\n }\n // This is normal priority\n normal.send('socket', socket);\n});\nserver.listen(1337);
\nThe child.js
would receive the socket handle as the second argument passed\nto the event callback function:\n\n
process.on('message', (m, socket) => {\n if (m === 'socket') {\n socket.end(`Request handled with ${process.argv[2]} priority`);\n }\n});
\nOnce a socket has been passed to a child, the parent is no longer capable of\ntracking when the socket is destroyed. To indicate this, the .connections
\nproperty becomes null
. It is recommended not to use .maxConnections
when\nthis occurs.\n\n
Note: this function uses [JSON.stringify()
][] internally to serialize the\nmessage
.\n\n
A single instance of Node.js runs in a single thread. To take advantage of\nmulti-core systems the user will sometimes want to launch a cluster of Node.js\nprocesses to handle the load.\n\n
\nThe cluster module allows you to easily create child processes that\nall share server ports.\n\n
\nconst cluster = require('cluster');\nconst http = require('http');\nconst numCPUs = require('os').cpus().length;\n\nif (cluster.isMaster) {\n // Fork workers.\n for (var i = 0; i < numCPUs; i++) {\n cluster.fork();\n }\n\n cluster.on('exit', (worker, code, signal) => {\n console.log(`worker ${worker.process.pid} died`);\n });\n} else {\n // Workers can share any TCP connection\n // In this case it is an HTTP server\n http.createServer((req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n }).listen(8000);\n}
\nRunning Node.js will now share port 8000 between the workers:\n\n
\n$ NODE_DEBUG=cluster node server.js\n23521,Master Worker 23524 online\n23521,Master Worker 23526 online\n23521,Master Worker 23523 online\n23521,Master Worker 23528 online
\nPlease note that, on Windows, it is not yet possible to set up a named pipe\nserver in a worker.\n\n
\n", "miscs": [ { "textRaw": "How It Works", "name": "How It Works", "type": "misc", "desc": "The worker processes are spawned using the [child_process.fork()
][] method,\nso that they can communicate with the parent via IPC and pass server\nhandles back and forth.\n\n
The cluster module supports two methods of distributing incoming\nconnections.\n\n
\nThe first one (and the default one on all platforms except Windows),\nis the round-robin approach, where the master process listens on a\nport, accepts new connections and distributes them across the workers\nin a round-robin fashion, with some built-in smarts to avoid\noverloading a worker process.\n\n
\nThe second approach is where the master process creates the listen\nsocket and sends it to interested workers. The workers then accept\nincoming connections directly.\n\n
\nThe second approach should, in theory, give the best performance.\nIn practice however, distribution tends to be very unbalanced due\nto operating system scheduler vagaries. Loads have been observed\nwhere over 70% of all connections ended up in just two processes,\nout of a total of eight.\n\n
\nBecause server.listen()
hands off most of the work to the master\nprocess, there are three cases where the behavior between a normal\nNode.js process and a cluster worker differs:\n\n
server.listen({fd: 7})
Because the message is passed to the master,\nfile descriptor 7 in the parent will be listened on, and the\nhandle passed to the worker, rather than listening to the worker's\nidea of what the number 7 file descriptor references.server.listen(handle)
Listening on handles explicitly will cause\nthe worker to use the supplied handle, rather than talk to the master\nprocess. If the worker already has the handle, then it's presumed\nthat you know what you are doing.server.listen(0)
Normally, this will cause servers to listen on a\nrandom port. However, in a cluster, each worker will receive the\nsame "random" port each time they do listen(0)
. In essence, the\nport is random the first time, but predictable thereafter. If you\nwant to listen on a unique port, generate a port number based on the\ncluster worker ID.There is no routing logic in Node.js, or in your program, and no shared\nstate between the workers. Therefore, it is important to design your\nprogram such that it does not rely too heavily on in-memory data objects\nfor things like sessions and login.\n\n
\nBecause workers are all separate processes, they can be killed or\nre-spawned depending on your program's needs, without affecting other\nworkers. As long as there are some workers still alive, the server will\ncontinue to accept connections. If no workers are alive, existing connections\nwill be dropped and new connections will be refused. Node.js does not\nautomatically manage the number of workers for you, however. It is your\nresponsibility to manage the worker pool for your application's needs.\n\n\n\n
\n" } ], "classes": [ { "textRaw": "Class: Worker", "type": "class", "name": "Worker", "desc": "A Worker object contains all public information and method about a worker.\nIn the master it can be obtained using cluster.workers
. In a worker\nit can be obtained using cluster.worker
.\n\n
Similar to the cluster.on('disconnect')
event, but specific to this worker.\n\n
cluster.fork().on('disconnect', () => {\n // Worker has disconnected\n});
\n",
"params": []
},
{
"textRaw": "Event: 'error'",
"type": "event",
"name": "error",
"desc": "This event is the same as the one provided by [child_process.fork()
][].\n\n
In a worker you can also use process.on('error')
.\n\n
Similar to the cluster.on('exit')
event, but specific to this worker.\n\n
const worker = cluster.fork();\nworker.on('exit', (code, signal) => {\n if (signal) {\n console.log(`worker was killed by signal: ${signal}`);\n } else if (code !== 0) {\n console.log(`worker exited with error code: ${code}`);\n } else {\n console.log('worker success!');\n }\n});
\n"
},
{
"textRaw": "Event: 'listening'",
"type": "event",
"name": "listening",
"params": [],
"desc": "Similar to the cluster.on('listening')
event, but specific to this worker.\n\n
cluster.fork().on('listening', (address) => {\n // Worker is listening\n});
\nIt is not emitted in the worker.\n\n
\n" }, { "textRaw": "Event: 'message'", "type": "event", "name": "message", "params": [], "desc": "Similar to the cluster.on('message')
event, but specific to this worker.\n\n
This event is the same as the one provided by [child_process.fork()
][].\n\n
In a worker you can also use process.on('message')
.\n\n
As an example, here is a cluster that keeps count of the number of requests\nin the master process using the message system:\n\n
\nconst cluster = require('cluster');\nconst http = require('http');\n\nif (cluster.isMaster) {\n\n // Keep track of http requests\n var numReqs = 0;\n setInterval(() => {\n console.log('numReqs =', numReqs);\n }, 1000);\n\n // Count requests\n function messageHandler(msg) {\n if (msg.cmd && msg.cmd == 'notifyRequest') {\n numReqs += 1;\n }\n }\n\n // Start workers and listen for messages containing notifyRequest\n const numCPUs = require('os').cpus().length;\n for (var i = 0; i < numCPUs; i++) {\n cluster.fork();\n }\n\n Object.keys(cluster.workers).forEach((id) => {\n cluster.workers[id].on('message', messageHandler);\n });\n\n} else {\n\n // Worker processes have a http server.\n http.Server((req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n\n // notify master about the request\n process.send({ cmd: 'notifyRequest' });\n }).listen(8000);\n}
\n"
},
{
"textRaw": "Event: 'online'",
"type": "event",
"name": "online",
"desc": "Similar to the cluster.on('online')
event, but specific to this worker.\n\n
cluster.fork().on('online', () => {\n // Worker is online\n});
\nIt is not emitted in the worker.\n\n
\n", "params": [] } ], "methods": [ { "textRaw": "worker.disconnect()", "type": "method", "name": "disconnect", "desc": "In a worker, this function will close all servers, wait for the 'close'
event on\nthose servers, and then disconnect the IPC channel.\n\n
In the master, an internal message is sent to the worker causing it to call\n.disconnect()
on itself.\n\n
Causes .exitedAfterDisconnect
to be set.\n\n
Note that after a server is closed, it will no longer accept new connections,\nbut connections may be accepted by any other listening worker. Existing\nconnections will be allowed to close as usual. When no more connections exist,\nsee [server.close()
][], the IPC channel to the worker will close allowing it to\ndie gracefully.\n\n
The above applies only to server connections, client connections are not\nautomatically closed by workers, and disconnect does not wait for them to close\nbefore exiting.\n\n
\nNote that in a worker, process.disconnect
exists, but it is not this function,\nit is [disconnect
][].\n\n
Because long living server connections may block workers from disconnecting, it\nmay be useful to send a message, so application specific actions may be taken to\nclose them. It also may be useful to implement a timeout, killing a worker if\nthe 'disconnect'
event has not been emitted after some time.\n\n
if (cluster.isMaster) {\n var worker = cluster.fork();\n var timeout;\n\n worker.on('listening', (address) => {\n worker.send('shutdown');\n worker.disconnect();\n timeout = setTimeout(() => {\n worker.kill();\n }, 2000);\n });\n\n worker.on('disconnect', () => {\n clearTimeout(timeout);\n });\n\n} else if (cluster.isWorker) {\n const net = require('net');\n var server = net.createServer((socket) => {\n // connections never end\n });\n\n server.listen(8000);\n\n process.on('message', (msg) => {\n if (msg === 'shutdown') {\n // initiate graceful close of any connections to server\n }\n });\n}
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "worker.isConnected()",
"type": "method",
"name": "isConnected",
"desc": "This function returns true
if the worker is connected to its master via its IPC\nchannel, false
otherwise. A worker is connected to its master after it's been\ncreated. It is disconnected after the 'disconnect'
event is emitted.\n\n
This function returns true
if the worker's process has terminated (either\nbecause of exiting or being signaled). Otherwise, it returns false
.\n\n
This function will kill the worker. In the master, it does this by disconnecting\nthe worker.process
, and once disconnected, killing with signal
. In the\nworker, it does it by disconnecting the channel, and then exiting with code 0
.\n\n
Causes .exitedAfterDisconnect
to be set.\n\n
This method is aliased as worker.destroy()
for backwards compatibility.\n\n
Note that in a worker, process.kill()
exists, but it is not this function,\nit is [kill
][].\n\n
Send a message to a worker or master, optionally with a handle.\n\n
\nIn the master this sends a message to a specific worker. It is identical to\n[ChildProcess.send()
][].\n\n
In a worker this sends a message to the master. It is identical to\nprocess.send()
.\n\n
This example will echo back all messages from the master:\n\n
\nif (cluster.isMaster) {\n var worker = cluster.fork();\n worker.send('hi there');\n\n} else if (cluster.isWorker) {\n process.on('message', (msg) => {\n process.send(msg);\n });\n}
\n"
}
],
"properties": [
{
"textRaw": "`exitedAfterDisconnect` {Boolean} ",
"type": "Boolean",
"name": "exitedAfterDisconnect",
"desc": "Set by calling .kill()
or .disconnect()
. Until then, it is undefined
.\n\n
The boolean worker.exitedAfterDisconnect
lets you distinguish between voluntary\nand accidental exit, the master may choose not to respawn a worker based on\nthis value.\n\n
cluster.on('exit', (worker, code, signal) => {\n if (worker.exitedAfterDisconnect === true) {\n console.log('Oh, it was just voluntary – no need to worry');\n }\n});\n\n// kill worker\nworker.kill();
\n"
},
{
"textRaw": "`id` {Number} ",
"type": "Number",
"name": "id",
"desc": "Each new worker is given its own unique id, this id is stored in the\nid
.\n\n
While a worker is alive, this is the key that indexes it in\ncluster.workers\n\n
\n" }, { "textRaw": "`process` {ChildProcess} ", "type": "ChildProcess", "name": "process", "desc": "All workers are created using [child_process.fork()
][], the returned object\nfrom this function is stored as .process
. In a worker, the global process
\nis stored.\n\n
See: [Child Process module][]\n\n
\nNote that workers will call process.exit(0)
if the 'disconnect'
event occurs\non process
and .exitedAfterDisconnect
is not true
. This protects against\naccidental disconnection.\n\n
An alias to [worker.exitedAfterDisconnect
][].\n\n
Set by calling .kill()
or .disconnect()
. Until then, it is undefined
.\n\n
The boolean worker.suicide
lets you distinguish between voluntary\nand accidental exit, the master may choose not to respawn a worker based on\nthis value.\n\n
cluster.on('exit', (worker, code, signal) => {\n if (worker.suicide === true) {\n console.log('Oh, it was just voluntary – no need to worry');\n }\n});\n\n// kill worker\nworker.kill();
\nThis API only exists for backwards compatibility and will be removed in the\nfuture.\n\n
\n" } ] } ], "events": [ { "textRaw": "Event: 'disconnect'", "type": "event", "name": "disconnect", "params": [], "desc": "Emitted after the worker IPC channel has disconnected. This can occur when a\nworker exits gracefully, is killed, or is disconnected manually (such as with\nworker.disconnect()).\n\n
\nThere may be a delay between the 'disconnect'
and 'exit'
events. These events\ncan be used to detect if the process is stuck in a cleanup or if there are\nlong-living connections.\n\n
cluster.on('disconnect', (worker) => {\n console.log(`The worker #${worker.id} has disconnected`);\n});
\n"
},
{
"textRaw": "Event: 'exit'",
"type": "event",
"name": "exit",
"params": [],
"desc": "When any of the workers die the cluster module will emit the 'exit'
event.\n\n
This can be used to restart the worker by calling .fork()
again.\n\n
cluster.on('exit', (worker, code, signal) => {\n console.log('worker %d died (%s). restarting...',\n worker.process.pid, signal || code);\n cluster.fork();\n});
\nSee [child_process event: 'exit'][].\n\n
\n" }, { "textRaw": "Event: 'fork'", "type": "event", "name": "fork", "params": [], "desc": "When a new worker is forked the cluster module will emit a 'fork'
event.\nThis can be used to log worker activity, and create your own timeout.\n\n
var timeouts = [];\nfunction errorMsg() {\n console.error('Something must be wrong with the connection ...');\n}\n\ncluster.on('fork', (worker) => {\n timeouts[worker.id] = setTimeout(errorMsg, 2000);\n});\ncluster.on('listening', (worker, address) => {\n clearTimeout(timeouts[worker.id]);\n});\ncluster.on('exit', (worker, code, signal) => {\n clearTimeout(timeouts[worker.id]);\n errorMsg();\n});
\n"
},
{
"textRaw": "Event: 'listening'",
"type": "event",
"name": "listening",
"params": [],
"desc": "After calling listen()
from a worker, when the 'listening'
event is emitted on\nthe server, a 'listening'
event will also be emitted on cluster
in the master.\n\n
The event handler is executed with two arguments, the worker
contains the worker\nobject and the address
object contains the following connection properties:\naddress
, port
and addressType
. This is very useful if the worker is listening\non more than one address.\n\n
cluster.on('listening', (worker, address) => {\n console.log(\n `A worker is now connected to ${address.address}:${address.port}`);\n});
\nThe addressType
is one of:\n\n
4
(TCPv4)6
(TCPv6)-1
(unix domain socket)"udp4"
or "udp6"
(UDP v4 or v6)Emitted when any worker receives a message.\n\n
\nSee [child_process event: 'message'][].\n\n
\nBefore Node.js v6.0, this event emitted only the message and the handle,\nbut not the worker object, contrary to what the documentation stated.\n\n
\nIf you need to support older versions and don't need the worker object,\nyou can work around the discrepancy by checking the number of arguments:\n\n
\ncluster.on('message', function(worker, message, handle) {\n if (arguments.length === 2) {\n handle = message;\n message = worker;\n worker = undefined;\n }\n // ...\n});
\n"
},
{
"textRaw": "Event: 'online'",
"type": "event",
"name": "online",
"params": [],
"desc": "After forking a new worker, the worker should respond with an online message.\nWhen the master receives an online message it will emit this event.\nThe difference between 'fork'
and 'online'
is that fork is emitted when the\nmaster forks a worker, and 'online' is emitted when the worker is running.\n\n
cluster.on('online', (worker) => {\n console.log('Yay, the worker responded after it was forked');\n});
\n"
},
{
"textRaw": "Event: 'setup'",
"type": "event",
"name": "setup",
"params": [],
"desc": "Emitted every time .setupMaster()
is called.\n\n
The settings
object is the cluster.settings
object at the time\n.setupMaster()
was called and is advisory only, since multiple calls to\n.setupMaster()
can be made in a single tick.\n\n
If accuracy is important, use cluster.settings
.\n\n
Calls .disconnect()
on each worker in cluster.workers
.\n\n
When they are disconnected all internal handles will be closed, allowing the\nmaster process to die gracefully if no other event is waiting.\n\n
\nThe method takes an optional callback argument which will be called when finished.\n\n
\nThis can only be called from the master process.\n\n
\n" }, { "textRaw": "cluster.fork([env])", "type": "method", "name": "fork", "signatures": [ { "return": { "textRaw": "return {cluster.Worker} ", "name": "return", "type": "cluster.Worker" }, "params": [ { "textRaw": "`env` {Object} Key/value pairs to add to worker process environment. ", "name": "env", "type": "Object", "desc": "Key/value pairs to add to worker process environment.", "optional": true } ] }, { "params": [ { "name": "env", "optional": true } ] } ], "desc": "Spawn a new worker process.\n\n
\nThis can only be called from the master process.\n\n
\n" }, { "textRaw": "cluster.setupMaster([settings])", "type": "method", "name": "setupMaster", "signatures": [ { "params": [ { "textRaw": "`settings` {Object} ", "options": [ { "textRaw": "`exec` {String} file path to worker file. (Default=`process.argv[1]`) ", "name": "exec", "default": "process.argv[1]", "type": "String", "desc": "file path to worker file." }, { "textRaw": "`args` {Array} string arguments passed to worker. (Default=`process.argv.slice(2)`) ", "name": "args", "default": "process.argv.slice(2)", "type": "Array", "desc": "string arguments passed to worker." }, { "textRaw": "`silent` {Boolean} whether or not to send output to parent's stdio. (Default=`false`) ", "name": "silent", "default": "false", "type": "Boolean", "desc": "whether or not to send output to parent's stdio." } ], "name": "settings", "type": "Object", "optional": true } ] }, { "params": [ { "name": "settings", "optional": true } ] } ], "desc": "setupMaster
is used to change the default 'fork' behavior. Once called,\nthe settings will be present in cluster.settings
.\n\n
Note that:\n\n
\n.fork()
and have no\neffect on workers that are already running.setupMaster()
is\nthe env
passed to .fork()
cluster.setupMaster()
is calledExample:\n\n
\nconst cluster = require('cluster');\ncluster.setupMaster({\n exec: 'worker.js',\n args: ['--use', 'https'],\n silent: true\n});\ncluster.fork(); // https worker\ncluster.setupMaster({\n exec: 'worker.js',\n args: ['--use', 'http']\n});\ncluster.fork(); // http worker
\nThis can only be called from the master process.\n\n
\n" } ], "properties": [ { "textRaw": "`isMaster` {Boolean} ", "type": "Boolean", "name": "isMaster", "desc": "True if the process is a master. This is determined\nby the process.env.NODE_UNIQUE_ID
. If process.env.NODE_UNIQUE_ID
is\nundefined, then isMaster
is true
.\n\n
True if the process is not a master (it is the negation of cluster.isMaster
).\n\n
The scheduling policy, either cluster.SCHED_RR
for round-robin or\ncluster.SCHED_NONE
to leave it to the operating system. This is a\nglobal setting and effectively frozen once you spawn the first worker\nor call cluster.setupMaster()
, whatever comes first.\n\n
SCHED_RR
is the default on all operating systems except Windows.\nWindows will change to SCHED_RR
once libuv is able to effectively\ndistribute IOCP handles without incurring a large performance hit.\n\n
cluster.schedulingPolicy
can also be set through the\nNODE_CLUSTER_SCHED_POLICY
environment variable. Valid\nvalues are "rr"
and "none"
.\n\n
After calling .setupMaster()
(or .fork()
) this settings object will contain\nthe settings, including the default values.\n\n
It is effectively frozen after being set, because .setupMaster()
can\nonly be called once.\n\n
This object is not supposed to be changed or set manually, by you.\n\n
\n" }, { "textRaw": "`worker` {Object} ", "type": "Object", "name": "worker", "desc": "A reference to the current worker object. Not available in the master process.\n\n
\nconst cluster = require('cluster');\n\nif (cluster.isMaster) {\n console.log('I am master');\n cluster.fork();\n cluster.fork();\n} else if (cluster.isWorker) {\n console.log(`I am worker #${cluster.worker.id}`);\n}
\n"
},
{
"textRaw": "`workers` {Object} ",
"type": "Object",
"name": "workers",
"desc": "A hash that stores the active worker objects, keyed by id
field. Makes it\neasy to loop through all the workers. It is only available in the master\nprocess.\n\n
A worker is removed from cluster.workers after the worker has disconnected and\nexited. The order between these two events cannot be determined in advance.\nHowever, it is guaranteed that the removal from the cluster.workers list happens\nbefore last 'disconnect'
or 'exit'
event is emitted.\n\n
// Go through all workers\nfunction eachWorker(callback) {\n for (var id in cluster.workers) {\n callback(cluster.workers[id]);\n }\n}\neachWorker((worker) => {\n worker.send('big announcement to all workers');\n});
\nShould you wish to reference a worker over a communication channel, using\nthe worker's unique id is the easiest way to find the worker.\n\n
\nsocket.on('data', (id) => {\n var worker = cluster.workers[id];\n});
\n"
}
],
"type": "module",
"displayName": "Cluster"
},
{
"textRaw": "Console",
"name": "console",
"stability": 2,
"stabilityText": "Stable",
"desc": "The console
module provides a simple debugging console that is similar to the\nJavaScript console mechanism provided by web browsers.\n\n
The module exports two specific components:\n\n
\nConsole
class with methods such as console.log()
, console.error()
and\nconsole.warn()
that can be used to write to any Node.js stream.console
instance configured to write to stdout
and stderr
.\nBecause this object is global, it can be used without calling\nrequire('console')
.Example using the global console
:\n\n
console.log('hello world');\n // Prints: hello world, to stdout\nconsole.log('hello %s', 'world');\n // Prints: hello world, to stdout\nconsole.error(new Error('Whoops, something bad happened'));\n // Prints: [Error: Whoops, something bad happened], to stderr\n\nconst name = 'Will Robinson';\nconsole.warn(`Danger ${name}! Danger!`);\n // Prints: Danger Will Robinson! Danger!, to stderr
\nExample using the Console
class:\n\n
const out = getStreamSomehow();\nconst err = getStreamSomehow();\nconst myConsole = new console.Console(out, err);\n\nmyConsole.log('hello world');\n // Prints: hello world, to out\nmyConsole.log('hello %s', 'world');\n // Prints: hello world, to out\nmyConsole.error(new Error('Whoops, something bad happened'));\n // Prints: [Error: Whoops, something bad happened], to err\n\nconst name = 'Will Robinson';\nmyConsole.warn(`Danger ${name}! Danger!`);\n // Prints: Danger Will Robinson! Danger!, to err
\nWhile the API for the Console
class is designed fundamentally around the\nbrowser console
object, the Console
in Node.js is not intended to\nduplicate the browser's functionality exactly.\n\n
The console functions are asynchronous unless the destination is a file.\nDisks are fast and operating systems normally employ write-back caching;\nit should be a very rare occurrence indeed that a write blocks, but it\nis possible.\n\n
\n", "type": "module", "displayName": "Asynchronous vs Synchronous Consoles" } ], "classes": [ { "textRaw": "Class: Console", "type": "class", "name": "Console", "desc": "The Console
class can be used to create a simple logger with configurable\noutput streams and can be accessed using either require('console').Console
\nor console.Console
:\n\n
const Console = require('console').Console;\nconst Console = console.Console;
\n",
"methods": [
{
"textRaw": "console.assert(value[, message][, ...])",
"type": "method",
"name": "assert",
"desc": "A simple assertion test that verifies whether value
is truthy. If it is not,\nan AssertionError
is thrown. If provided, the error message
is formatted\nusing [util.format()
][] and used as the error message.\n\n
console.assert(true, 'does nothing');\n // OK\nconsole.assert(false, 'Whoops %s', 'didn\\'t work');\n // AssertionError: Whoops didn't work
\nNote: the console.assert()
method is implemented differently in Node.js\nthan the console.assert()
method [available in browsers][web-api-assert].\n\n
Specifically, in browsers, calling console.assert()
with a falsy\nassertion will cause the message
to be printed to the console without\ninterrupting execution of subsequent code. In Node.js, however, a falsy\nassertion will cause an AssertionError
to be thrown.\n\n
Functionality approximating that implemented by browsers can be implemented\nby extending Node.js' console
and overriding the console.assert()
method.\n\n
In the following example, a simple module is created that extends and overrides\nthe default behavior of console
in Node.js.\n\n
'use strict';\n\n// Creates a simple extension of console with a\n// new impl for assert without monkey-patching.\nconst myConsole = Object.setPrototypeOf({\n assert(assertion, message, ...args) {\n try {\n console.assert(assertion, message, ...args);\n } catch (err) {\n console.error(err.stack);\n }\n }\n}, console);\n\nmodule.exports = myConsole;
\nThis can then be used as a direct replacement for the built in console:\n\n
\nconst console = require('./myConsole');\nconsole.assert(false, 'this message will print, but no error thrown');\nconsole.log('this will also print');
\n",
"signatures": [
{
"params": [
{
"name": "value"
},
{
"name": "message",
"optional": true
},
{
"name": "...",
"optional": true
}
]
}
]
},
{
"textRaw": "console.dir(obj[, options])",
"type": "method",
"name": "dir",
"desc": "Uses [util.inspect()
][] on obj
and prints the resulting string to stdout
.\nThis function bypasses any custom inspect()
function defined on obj
. An\noptional options
object may be passed to alter certain aspects of the\nformatted string:\n\n
showHidden
- if true
then the object's non-enumerable and symbol\nproperties will be shown too. Defaults to false
.
depth
- tells [util.inspect()
][] how many times to recurse while\nformatting the object. This is useful for inspecting large complicated objects.\nDefaults to 2
. To make it recurse indefinitely, pass null
.
colors
- if true
, then the output will be styled with ANSI color codes.\nDefaults to false
. Colors are customizable; see\n[customizing util.inspect()
colors][].
Prints to stderr
with newline. Multiple arguments can be passed, with the\nfirst used as the primary message and all additional used as substitution\nvalues similar to printf(3)
(the arguments are all passed to\n[util.format()
][]).\n\n
const code = 5;\nconsole.error('error #%d', code);\n // Prints: error #5, to stderr\nconsole.error('error', code);\n // Prints: error 5, to stderr
\nIf formatting elements (e.g. %d
) are not found in the first string then\n[util.inspect()
][] is called on each argument and the resulting string\nvalues are concatenated. See [util.format()
][] for more information.\n\n
The console.info()
function is an alias for [console.log()
][].\n\n
Prints to stdout
with newline. Multiple arguments can be passed, with the\nfirst used as the primary message and all additional used as substitution\nvalues similar to printf(3)
(the arguments are all passed to\n[util.format()
][]).\n\n
var count = 5;\nconsole.log('count: %d', count);\n // Prints: count: 5, to stdout\nconsole.log('count: ', count);\n // Prints: count: 5, to stdout
\nIf formatting elements (e.g. %d
) are not found in the first string then\n[util.inspect()
][] is called on each argument and the resulting string\nvalues are concatenated. See [util.format()
][] for more information.\n\n
Starts a timer that can be used to compute the duration of an operation. Timers\nare identified by a unique label
. Use the same label
when you call\n[console.timeEnd()
][] to stop the timer and output the elapsed time in\nmilliseconds to stdout. Timer durations are accurate to the sub-millisecond.\n\n
Stops a timer that was previously started by calling [console.time()
][] and\nprints the result to stdout:\n\n
console.time('100-elements');\nfor (var i = 0; i < 100; i++) {\n ;\n}\nconsole.timeEnd('100-elements');\n// prints 100-elements: 225.438ms
\nNote: As of Node.js v6.0.0, console.timeEnd()
deletes the timer to avoid\nleaking it. On older versions, the timer persisted. This allowed\nconsole.timeEnd()
to be called multiple times for the same label. This\nfunctionality was unintended and is no longer supported.\n\n
Prints to stderr
the string 'Trace :'
, followed by the [util.format()
][]\nformatted message and stack trace to the current position in the code.\n\n
console.trace('Show me');\n // Prints: (stack trace will vary based on where trace is called)\n // Trace: Show me\n // at repl:2:9\n // at REPLServer.defaultEval (repl.js:248:27)\n // at bound (domain.js:287:14)\n // at REPLServer.runBound [as eval] (domain.js:300:12)\n // at REPLServer.<anonymous> (repl.js:412:12)\n // at emitOne (events.js:82:20)\n // at REPLServer.emit (events.js:169:7)\n // at REPLServer.Interface._onLine (readline.js:210:10)\n // at REPLServer.Interface._line (readline.js:549:8)\n // at REPLServer.Interface._ttyWrite (readline.js:826:14)
\n",
"signatures": [
{
"params": [
{
"name": "message"
},
{
"name": "...",
"optional": true
}
]
}
]
},
{
"textRaw": "console.warn([data][, ...])",
"type": "method",
"name": "warn",
"desc": "The console.warn()
function is an alias for [console.error()
][].\n\n
Creates a new Console
by passing one or two writable stream instances.\nstdout
is a writable stream to print log or info output. stderr
\nis used for warning or error output. If stderr
isn't passed, warning and error\noutput will be sent to stdout
.\n\n
const output = fs.createWriteStream('./stdout.log');\nconst errorOutput = fs.createWriteStream('./stderr.log');\n// custom simple logger\nconst logger = new Console(output, errorOutput);\n// use it like console\nvar count = 5;\nlogger.log('count: %d', count);\n// in stdout.log: count 5
\nThe global console
is a special Console
whose output is sent to\n[process.stdout
][] and [process.stderr
][]. It is equivalent to calling:\n\n
new Console(process.stdout, process.stderr);
\n"
}
]
}
],
"type": "module",
"displayName": "Console"
},
{
"textRaw": "Crypto",
"name": "crypto",
"stability": 2,
"stabilityText": "Stable",
"desc": "The crypto
module provides cryptographic functionality that includes a set of\nwrappers for OpenSSL's hash, HMAC, cipher, decipher, sign and verify functions.\n\n
Use require('crypto')
to access this module.\n\n
const crypto = require('crypto');\n\nconst secret = 'abcdefg';\nconst hash = crypto.createHmac('sha256', secret)\n .update('I love cupcakes')\n .digest('hex');\nconsole.log(hash);\n // Prints:\n // c0fa1bc00531bd78ef38c628449c5102aeabd49b5dc3a2a516ea6ea959d6658e
\n",
"modules": [
{
"textRaw": "Determining if crypto support is unavailable",
"name": "determining_if_crypto_support_is_unavailable",
"desc": "It is possible for Node.js to be built without including support for the\ncrypto
module. In such cases, calling require('crypto')
will result in an\nerror being thrown.\n\n
var crypto;\ntry {\n crypto = require('crypto');\n} catch (err) {\n console.log('crypto support is disabled!');\n}
\n",
"type": "module",
"displayName": "Determining if crypto support is unavailable"
},
{
"textRaw": "`crypto` module methods and properties",
"name": "`crypto`_module_methods_and_properties",
"properties": [
{
"textRaw": "crypto.DEFAULT_ENCODING",
"name": "DEFAULT_ENCODING",
"desc": "The default encoding to use for functions that can take either strings\nor [buffers][Buffer
]. The default value is 'buffer'
, which makes methods\ndefault to [Buffer
][] objects.\n\n
The crypto.DEFAULT_ENCODING
mechanism is provided for backwards compatibility\nwith legacy programs that expect 'binary'
to be the default encoding.\n\n
New applications should expect the default to be 'buffer'
. This property may\nbecome deprecated in a future Node.js release.\n\n
Property for checking and controlling whether a FIPS compliant crypto provider is\ncurrently in use. Setting to true requires a FIPS build of Node.js.\n\n
\n" } ], "methods": [ { "textRaw": "crypto.createCipher(algorithm, password)", "type": "method", "name": "createCipher", "desc": "Creates and returns a Cipher
object that uses the given algorithm
and\npassword
.\n\n
The algorithm
is dependent on OpenSSL, examples are 'aes192'
, etc. On\nrecent OpenSSL releases, openssl list-cipher-algorithms
will display the\navailable cipher algorithms.\n\n
The password
is used to derive the cipher key and initialization vector (IV).\nThe value must be either a 'binary'
encoded string or a [Buffer
][].\n\n
The implementation of crypto.createCipher()
derives keys using the OpenSSL\nfunction [EVP_BytesToKey
][] with the digest algorithm set to MD5, one\niteration, and no salt. The lack of salt allows dictionary attacks as the same\npassword always creates the same key. The low iteration count and\nnon-cryptographically secure hash algorithm allow passwords to be tested very\nrapidly.\n\n
In line with OpenSSL's recommendation to use pbkdf2 instead of\n[EVP_BytesToKey
][] it is recommended that developers derive a key and IV on\ntheir own using [crypto.pbkdf2()
][] and to use [crypto.createCipheriv()
][]\nto create the Cipher
object.\n\n
Creates and returns a Cipher
object, with the given algorithm
, key
and\ninitialization vector (iv
).\n\n
The algorithm
is dependent on OpenSSL, examples are 'aes192'
, etc. On\nrecent OpenSSL releases, openssl list-cipher-algorithms
will display the\navailable cipher algorithms.\n\n
The key
is the raw key used by the algorithm
and iv
is an\n[initialization vector][]. Both arguments must be 'binary'
encoded strings or\n[buffers][Buffer
].\n\n
The crypto.createCredentials()
method is a deprecated alias for creating\nand returning a tls.SecureContext
object. The crypto.createCredentials()
\nmethod should not be used.\n\n
The optional details
argument is a hash object with keys:\n\n
pfx
: {String|Buffer} - PFX or PKCS12 encoded private\nkey, certificate and CA certificateskey
: {String} - PEM encoded private keypassphrase
: {String} - passphrase for the private key or PFXcert
: {String} - PEM encoded certificateca
: {String|Array} - Either a string or array of strings of PEM encoded CA\ncertificates to trust.crl
: {String|Array} - Either a string or array of strings of PEM encoded CRLs\n(Certificate Revocation List)ciphers
: {String} using the [OpenSSL cipher list format][] describing the\ncipher algorithms to use or exclude.If no 'ca' details are given, Node.js will use Mozilla's default\n[publicly trusted list of CAs][].\n\n
\n", "signatures": [ { "params": [ { "name": "details" } ] } ] }, { "textRaw": "crypto.createDecipher(algorithm, password)", "type": "method", "name": "createDecipher", "desc": "Creates and returns a Decipher
object that uses the given algorithm
and\npassword
(key).\n\n
The implementation of crypto.createDecipher()
derives keys using the OpenSSL\nfunction [EVP_BytesToKey
][] with the digest algorithm set to MD5, one\niteration, and no salt. The lack of salt allows dictionary attacks as the same\npassword always creates the same key. The low iteration count and\nnon-cryptographically secure hash algorithm allow passwords to be tested very\nrapidly.\n\n
In line with OpenSSL's recommendation to use pbkdf2 instead of\n[EVP_BytesToKey
][] it is recommended that developers derive a key and IV on\ntheir own using [crypto.pbkdf2()
][] and to use [crypto.createDecipheriv()
][]\nto create the Decipher
object.\n\n
Creates and returns a Decipher
object that uses the given algorithm
, key
\nand initialization vector (iv
).\n\n
The algorithm
is dependent on OpenSSL, examples are 'aes192'
, etc. On\nrecent OpenSSL releases, openssl list-cipher-algorithms
will display the\navailable cipher algorithms.\n\n
The key
is the raw key used by the algorithm
and iv
is an\n[initialization vector][]. Both arguments must be 'binary'
encoded strings or\n[buffers][Buffer
].\n\n
Creates a DiffieHellman
key exchange object using the supplied prime
and an\noptional specific generator
.\n\n
The generator
argument can be a number, string, or [Buffer
][]. If\ngenerator
is not specified, the value 2
is used.\n\n
The prime_encoding
and generator_encoding
arguments can be 'binary'
,\n'hex'
, or 'base64'
.\n\n
If prime_encoding
is specified, prime
is expected to be a string; otherwise\na [Buffer
][] is expected.\n\n
If generator_encoding
is specified, generator
is expected to be a string;\notherwise either a number or [Buffer
][] is expected.\n\n
Creates a DiffieHellman
key exchange object and generates a prime of\nprime_length
bits using an optional specific numeric generator
.\nIf generator
is not specified, the value 2
is used.\n\n
Creates an Elliptic Curve Diffie-Hellman (ECDH
) key exchange object using a\npredefined curve specified by the curve_name
string. Use\n[crypto.getCurves()
][] to obtain a list of available curve names. On recent\nOpenSSL releases, openssl ecparam -list_curves
will also display the name\nand description of each available elliptic curve.\n\n
Creates and returns a Hash
object that can be used to generate hash digests\nusing the given algorithm
.\n\n
The algorithm
is dependent on the available algorithms supported by the\nversion of OpenSSL on the platform. Examples are 'sha256'
, 'sha512'
, etc.\nOn recent releases of OpenSSL, openssl list-message-digest-algorithms
will\ndisplay the available digest algorithms.\n\n
Example: generating the sha256 sum of a file\n\n
\nconst filename = process.argv[2];\nconst crypto = require('crypto');\nconst fs = require('fs');\n\nconst hash = crypto.createHash('sha256');\n\nconst input = fs.createReadStream(filename);\ninput.on('readable', () => {\n var data = input.read();\n if (data)\n hash.update(data);\n else {\n console.log(`${hash.digest('hex')} ${filename}`);\n }\n});
\n",
"signatures": [
{
"params": [
{
"name": "algorithm"
}
]
}
]
},
{
"textRaw": "crypto.createHmac(algorithm, key)",
"type": "method",
"name": "createHmac",
"desc": "Creates and returns an Hmac
object that uses the given algorithm
and key
.\n\n
The algorithm
is dependent on the available algorithms supported by the\nversion of OpenSSL on the platform. Examples are 'sha256'
, 'sha512'
, etc.\nOn recent releases of OpenSSL, openssl list-message-digest-algorithms
will\ndisplay the available digest algorithms.\n\n
The key
is the HMAC key used to generate the cryptographic HMAC hash.\n\n
Example: generating the sha256 HMAC of a file\n\n
\nconst filename = process.argv[2];\nconst crypto = require('crypto');\nconst fs = require('fs');\n\nconst hmac = crypto.createHmac('sha256', 'a secret');\n\nconst input = fs.createReadStream(filename);\ninput.on('readable', () => {\n var data = input.read();\n if (data)\n hmac.update(data);\n else {\n console.log(`${hmac.digest('hex')} ${filename}`);\n }\n});
\n",
"signatures": [
{
"params": [
{
"name": "algorithm"
},
{
"name": "key"
}
]
}
]
},
{
"textRaw": "crypto.createSign(algorithm)",
"type": "method",
"name": "createSign",
"desc": "Creates and returns a Sign
object that uses the given algorithm
. On\nrecent OpenSSL releases, openssl list-public-key-algorithms
will\ndisplay the available signing algorithms. One example is 'RSA-SHA256'
.\n\n
Creates and returns a Verify
object that uses the given algorithm. On\nrecent OpenSSL releases, openssl list-public-key-algorithms
will\ndisplay the available signing algorithms. One example is 'RSA-SHA256'
.\n\n
Returns an array with the names of the supported cipher algorithms.\n\n
\nExample:\n\n
\nconst ciphers = crypto.getCiphers();\nconsole.log(ciphers); // ['aes-128-cbc', 'aes-128-ccm', ...]
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "crypto.getCurves()",
"type": "method",
"name": "getCurves",
"desc": "Returns an array with the names of the supported elliptic curves.\n\n
\nExample:\n\n
\nconst curves = crypto.getCurves();\nconsole.log(curves); // ['secp256k1', 'secp384r1', ...]
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "crypto.getDiffieHellman(group_name)",
"type": "method",
"name": "getDiffieHellman",
"desc": "Creates a predefined DiffieHellman
key exchange object. The\nsupported groups are: 'modp1'
, 'modp2'
, 'modp5'
(defined in\n[RFC 2412][], but see [Caveats][]) and 'modp14'
, 'modp15'
,\n'modp16'
, 'modp17'
, 'modp18'
(defined in [RFC 3526][]). The\nreturned object mimics the interface of objects created by\n[crypto.createDiffieHellman()
][], but will not allow changing\nthe keys (with [diffieHellman.setPublicKey()
][] for example). The\nadvantage of using this method is that the parties do not have to\ngenerate nor exchange a group modulus beforehand, saving both processor\nand communication time.\n\n
Example (obtaining a shared secret):\n\n
\nconst crypto = require('crypto');\nconst alice = crypto.getDiffieHellman('modp14');\nconst bob = crypto.getDiffieHellman('modp14');\n\nalice.generateKeys();\nbob.generateKeys();\n\nconst alice_secret = alice.computeSecret(bob.getPublicKey(), null, 'hex');\nconst bob_secret = bob.computeSecret(alice.getPublicKey(), null, 'hex');\n\n/* alice_secret and bob_secret should be the same */\nconsole.log(alice_secret == bob_secret);
\n",
"signatures": [
{
"params": [
{
"name": "group_name"
}
]
}
]
},
{
"textRaw": "crypto.getHashes()",
"type": "method",
"name": "getHashes",
"desc": "Returns an array with the names of the supported hash algorithms.\n\n
\nExample:\n\n
\nconst hashes = crypto.getHashes();\nconsole.log(hashes); // ['sha', 'sha1', 'sha1WithRSAEncryption', ...]
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "crypto.pbkdf2(password, salt, iterations, keylen, digest, callback)",
"type": "method",
"name": "pbkdf2",
"desc": "Provides an asynchronous Password-Based Key Derivation Function 2 (PBKDF2)\nimplementation. A selected HMAC digest algorithm specified by digest
is\napplied to derive a key of the requested byte length (keylen
) from the\npassword
, salt
and iterations
.\n\n
The supplied callback
function is called with two arguments: err
and\nderivedKey
. If an error occurs, err
will be set; otherwise err
will be\nnull. The successfully generated derivedKey
will be passed as a [Buffer
][].\n\n
The iterations
argument must be a number set as high as possible. The\nhigher the number of iterations, the more secure the derived key will be,\nbut will take a longer amount of time to complete.\n\n
The salt
should also be as unique as possible. It is recommended that the\nsalts are random and their lengths are greater than 16 bytes. See\n[NIST SP 800-132][] for details.\n\n
Example:\n\n
\nconst crypto = require('crypto');\ncrypto.pbkdf2('secret', 'salt', 100000, 512, 'sha512', (err, key) => {\n if (err) throw err;\n console.log(key.toString('hex')); // 'c5e478d...1469e50'\n});
\nAn array of supported digest functions can be retrieved using\n[crypto.getHashes()
][].\n\n
Provides a synchronous Password-Based Key Derivation Function 2 (PBKDF2)\nimplementation. A selected HMAC digest algorithm specified by digest
is\napplied to derive a key of the requested byte length (keylen
) from the\npassword
, salt
and iterations
.\n\n
If an error occurs an Error will be thrown, otherwise the derived key will be\nreturned as a [Buffer
][].\n\n
The iterations
argument must be a number set as high as possible. The\nhigher the number of iterations, the more secure the derived key will be,\nbut will take a longer amount of time to complete.\n\n
The salt
should also be as unique as possible. It is recommended that the\nsalts are random and their lengths are greater than 16 bytes. See\n[NIST SP 800-132][] for details.\n\n
Example:\n\n
\nconst crypto = require('crypto');\nconst key = crypto.pbkdf2Sync('secret', 'salt', 100000, 512, 'sha512');\nconsole.log(key.toString('hex')); // 'c5e478d...1469e50'
\nAn array of supported digest functions can be retrieved using\n[crypto.getHashes()
][].\n\n
Decrypts buffer
with private_key
.\n\n
private_key
can be an object or a string. If private_key
is a string, it is\ntreated as the key with no passphrase and will use RSA_PKCS1_OAEP_PADDING
.\nIf private_key
is an object, it is interpreted as a hash object with the\nkeys:\n\n
key
: {String} - PEM encoded private keypassphrase
: {String} - Optional passphrase for the private keypadding
: An optional padding value, one of the following:constants.RSA_NO_PADDING
constants.RSA_PKCS1_PADDING
constants.RSA_PKCS1_OAEP_PADDING
All paddings are defined in the constants
module.\n\n
Encrypts buffer
with private_key
.\n\n
private_key
can be an object or a string. If private_key
is a string, it is\ntreated as the key with no passphrase and will use RSA_PKCS1_PADDING
.\nIf private_key
is an object, it is interpreted as a hash object with the\nkeys:\n\n
key
: {String} - PEM encoded private keypassphrase
: {String} - Optional passphrase for the private keypadding
: An optional padding value, one of the following:constants.RSA_NO_PADDING
constants.RSA_PKCS1_PADDING
constants.RSA_PKCS1_OAEP_PADDING
All paddings are defined in the constants
module.\n\n
Decrypts buffer
with public_key
.\n\n
public_key
can be an object or a string. If public_key
is a string, it is\ntreated as the key with no passphrase and will use RSA_PKCS1_PADDING
.\nIf public_key
is an object, it is interpreted as a hash object with the\nkeys:\n\n
key
: {String} - PEM encoded public keypassphrase
: {String} - Optional passphrase for the private keypadding
: An optional padding value, one of the following:constants.RSA_NO_PADDING
constants.RSA_PKCS1_PADDING
constants.RSA_PKCS1_OAEP_PADDING
Because RSA public keys can be derived from private keys, a private key may\nbe passed instead of a public key.\n\n
\nAll paddings are defined in the constants
module.\n\n
Encrypts buffer
with public_key
.\n\n
public_key
can be an object or a string. If public_key
is a string, it is\ntreated as the key with no passphrase and will use RSA_PKCS1_OAEP_PADDING
.\nIf public_key
is an object, it is interpreted as a hash object with the\nkeys:\n\n
key
: {String} - PEM encoded public keypassphrase
: {String} - Optional passphrase for the private keypadding
: An optional padding value, one of the following:constants.RSA_NO_PADDING
constants.RSA_PKCS1_PADDING
constants.RSA_PKCS1_OAEP_PADDING
Because RSA public keys can be derived from private keys, a private key may\nbe passed instead of a public key.\n\n
\nAll paddings are defined in the constants
module.\n\n
Generates cryptographically strong pseudo-random data. The size
argument\nis a number indicating the number of bytes to generate.\n\n
If a callback
function is provided, the bytes are generated asynchronously\nand the callback
function is invoked with two arguments: err
and buf
.\nIf an error occurs, err
will be an Error object; otherwise it is null. The\nbuf
argument is a [Buffer
][] containing the generated bytes.\n\n
// Asynchronous\nconst crypto = require('crypto');\ncrypto.randomBytes(256, (err, buf) => {\n if (err) throw err;\n console.log(`${buf.length} bytes of random data: ${buf.toString('hex')}`);\n});
\nIf the callback
function is not provided, the random bytes are generated\nsynchronously and returned as a [Buffer
][]. An error will be thrown if\nthere is a problem generating the bytes.\n\n
// Synchronous\nconst buf = crypto.randomBytes(256);\nconsole.log(\n `${buf.length} bytes of random data: ${buf.toString('hex')}`);
\nThe crypto.randomBytes()
method will block until there is sufficient entropy.\nThis should normally never take longer than a few milliseconds. The only time\nwhen generating the random bytes may conceivably block for a longer period of\ntime is right after boot, when the whole system is still low on entropy.\n\n
Load and set the engine
for some or all OpenSSL functions (selected by flags).\n\n
engine
could be either an id or a path to the engine's shared library.\n\n
The optional flags
argument uses ENGINE_METHOD_ALL
by default. The flags
\nis a bit field taking one of or a mix of the following flags (defined in the\nconstants
module):\n\n
ENGINE_METHOD_RSA
ENGINE_METHOD_DSA
ENGINE_METHOD_DH
ENGINE_METHOD_RAND
ENGINE_METHOD_ECDH
ENGINE_METHOD_ECDSA
ENGINE_METHOD_CIPHERS
ENGINE_METHOD_DIGESTS
ENGINE_METHOD_STORE
ENGINE_METHOD_PKEY_METHS
ENGINE_METHOD_PKEY_ASN1_METHS
ENGINE_METHOD_ALL
ENGINE_METHOD_NONE
The Crypto module was added to Node.js before there was the concept of a\nunified Stream API, and before there were [Buffer
][] objects for handling\nbinary data. As such, the many of the crypto
defined classes have methods not\ntypically found on other Node.js classes that implement the [streams][stream]\nAPI (e.g. update()
, final()
, or digest()
). Also, many methods accepted\nand returned 'binary'
encoded strings by default rather than Buffers. This\ndefault was changed after Node.js v0.8 to use [Buffer
][] objects by default\ninstead.\n\n
Usage of ECDH
with non-dynamically generated key pairs has been simplified.\nNow, [ecdh.setPrivateKey()
][] can be called with a preselected private key\nand the associated public point (key) will be computed and stored in the object.\nThis allows code to only store and provide the private part of the EC key pair.\n[ecdh.setPrivateKey()
][] now also validates that the private key is valid for\nthe selected curve.\n\n
The [ecdh.setPublicKey()
][] method is now deprecated as its inclusion in the\nAPI is not useful. Either a previously stored private key should be set, which\nautomatically generates the associated public key, or [ecdh.generateKeys()
][]\nshould be called. The main drawback of using [ecdh.setPublicKey()
][] is that\nit can be used to put the ECDH key pair into an inconsistent state.\n\n
The crypto
module still supports some algorithms which are already\ncompromised and are not currently recommended for use. The API also allows\nthe use of ciphers and hashes with a small key size that are considered to be\ntoo weak for safe use.\n\n
Users should take full responsibility for selecting the crypto\nalgorithm and key size according to their security requirements.\n\n
\nBased on the recommendations of [NIST SP 800-131A][]:\n\n
\nmodp1
, modp2
and modp5
have a key size\nsmaller than 2048 bits and are not recommended.See the reference for other recommendations and details.\n\n
\n", "type": "module", "displayName": "Support for weak or compromised algorithms" } ], "type": "module", "displayName": "Notes" } ], "classes": [ { "textRaw": "Class: Certificate", "type": "class", "name": "Certificate", "desc": "SPKAC is a Certificate Signing Request mechanism originally implemented by\nNetscape and now specified formally as part of [HTML5's keygen
element][].\n\n
The crypto
module provides the Certificate
class for working with SPKAC\ndata. The most common usage is handling output generated by the HTML5\n<keygen>
element. Node.js uses [OpenSSL's SPKAC implementation][] internally.\n\n
Instances of the Certificate
class can be created using the new
keyword\nor by calling crypto.Certificate()
as a function:\n\n
const crypto = require('crypto');\n\nconst cert1 = new crypto.Certificate();\nconst cert2 = crypto.Certificate();
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "certificate.exportChallenge(spkac)",
"type": "method",
"name": "exportChallenge",
"desc": "The spkac
data structure includes a public key and a challenge. The\ncertificate.exportChallenge()
returns the challenge component in the\nform of a Node.js [Buffer
][]. The spkac
argument can be either a string\nor a [Buffer
][].\n\n
const cert = require('crypto').Certificate();\nconst spkac = getSpkacSomehow();\nconst challenge = cert.exportChallenge(spkac);\nconsole.log(challenge.toString('utf8'));\n // Prints the challenge as a UTF8 string
\n",
"signatures": [
{
"params": [
{
"name": "spkac"
}
]
}
]
},
{
"textRaw": "certificate.exportPublicKey(spkac)",
"type": "method",
"name": "exportPublicKey",
"desc": "The spkac
data structure includes a public key and a challenge. The\ncertificate.exportPublicKey()
returns the public key component in the\nform of a Node.js [Buffer
][]. The spkac
argument can be either a string\nor a [Buffer
][].\n\n
const cert = require('crypto').Certificate();\nconst spkac = getSpkacSomehow();\nconst publicKey = cert.exportPublicKey(spkac);\nconsole.log(publicKey);\n // Prints the public key as <Buffer ...>
\n",
"signatures": [
{
"params": [
{
"name": "spkac"
}
]
}
]
},
{
"textRaw": "certificate.verifySpkac(spkac)",
"type": "method",
"name": "verifySpkac",
"desc": "Returns true
if the given spkac
data structure is valid, false
otherwise.\nThe spkac
argument must be a Node.js [Buffer
][].\n\n
const cert = require('crypto').Certificate();\nconst spkac = getSpkacSomehow();\nconsole.log(cert.verifySpkac(Buffer.from(spkac)));\n // Prints true or false
\n",
"signatures": [
{
"params": [
{
"name": "spkac"
}
]
}
]
}
]
},
{
"textRaw": "Class: Cipher",
"type": "class",
"name": "Cipher",
"desc": "Instances of the Cipher
class are used to encrypt data. The class can be\nused in one of two ways:\n\n
cipher.update()
][] and [cipher.final()
][] methods to produce\nthe encrypted data.The [crypto.createCipher()
][] or [crypto.createCipheriv()
][] methods are\nused to create Cipher
instances. Cipher
objects are not to be created\ndirectly using the new
keyword.\n\n
Example: Using Cipher
objects as streams:\n\n
const crypto = require('crypto');\nconst cipher = crypto.createCipher('aes192', 'a password');\n\nvar encrypted = '';\ncipher.on('readable', () => {\n var data = cipher.read();\n if (data)\n encrypted += data.toString('hex');\n});\ncipher.on('end', () => {\n console.log(encrypted);\n // Prints: ca981be48e90867604588e75d04feabb63cc007a8f8ad89b10616ed84d815504\n});\n\ncipher.write('some clear text data');\ncipher.end();
\nExample: Using Cipher
and piped streams:\n\n
const crypto = require('crypto');\nconst fs = require('fs');\nconst cipher = crypto.createCipher('aes192', 'a password');\n\nconst input = fs.createReadStream('test.js');\nconst output = fs.createWriteStream('test.enc');\n\ninput.pipe(cipher).pipe(output);
\nExample: Using the [cipher.update()
][] and [cipher.final()
][] methods:\n\n
const crypto = require('crypto');\nconst cipher = crypto.createCipher('aes192', 'a password');\n\nvar encrypted = cipher.update('some clear text data', 'utf8', 'hex');\nencrypted += cipher.final('hex');\nconsole.log(encrypted);\n // Prints: ca981be48e90867604588e75d04feabb63cc007a8f8ad89b10616ed84d815504
\n",
"methods": [
{
"textRaw": "cipher.final([output_encoding])",
"type": "method",
"name": "final",
"desc": "Returns any remaining enciphered contents. If output_encoding
\nparameter is one of 'binary'
, 'base64'
or 'hex'
, a string is returned.\nIf an output_encoding
is not provided, a [Buffer
][] is returned.\n\n
Once the cipher.final()
method has been called, the Cipher
object can no\nlonger be used to encrypt data. Attempts to call cipher.final()
more than\nonce will result in an error being thrown.\n\n
When using an authenticated encryption mode (only GCM
is currently\nsupported), the cipher.setAAD()
method sets the value used for the\nadditional authenticated data (AAD) input parameter.\n\n
When using an authenticated encryption mode (only GCM
is currently\nsupported), the cipher.getAuthTag()
method returns a [Buffer
][] containing\nthe authentication tag that has been computed from the given data.\n\n
The cipher.getAuthTag()
method should only be called after encryption has\nbeen completed using the [cipher.final()
][] method.\n\n
When using block encryption algorithms, the Cipher
class will automatically\nadd padding to the input data to the appropriate block size. To disable the\ndefault padding call cipher.setAutoPadding(false)
.\n\n
When auto_padding
is false
, the length of the entire input data must be a\nmultiple of the cipher's block size or [cipher.final()
][] will throw an Error.\nDisabling automatic padding is useful for non-standard padding, for instance\nusing 0x0
instead of PKCS padding.\n\n
The cipher.setAutoPadding()
method must be called before [cipher.final()
][].\n\n
Updates the cipher with data
. If the input_encoding
argument is given,\nit's value must be one of 'utf8'
, 'ascii'
, or 'binary'
and the data
\nargument is a string using the specified encoding. If the input_encoding
\nargument is not given, data
must be a [Buffer
][]. If data
is a\n[Buffer
][] then input_encoding
is ignored.\n\n
The output_encoding
specifies the output format of the enciphered\ndata, and can be 'binary'
, 'base64'
or 'hex'
. If the output_encoding
\nis specified, a string using the specified encoding is returned. If no\noutput_encoding
is provided, a [Buffer
][] is returned.\n\n
The cipher.update()
method can be called multiple times with new data until\n[cipher.final()
][] is called. Calling cipher.update()
after\n[cipher.final()
][] will result in an error being thrown.\n\n
Instances of the Decipher
class are used to decrypt data. The class can be\nused in one of two ways:\n\n
decipher.update()
][] and [decipher.final()
][] methods to\nproduce the unencrypted data.The [crypto.createDecipher()
][] or [crypto.createDecipheriv()
][] methods are\nused to create Decipher
instances. Decipher
objects are not to be created\ndirectly using the new
keyword.\n\n
Example: Using Decipher
objects as streams:\n\n
const crypto = require('crypto');\nconst decipher = crypto.createDecipher('aes192', 'a password');\n\nvar decrypted = '';\ndecipher.on('readable', () => {\n var data = decipher.read();\n if (data)\n decrypted += data.toString('utf8');\n});\ndecipher.on('end', () => {\n console.log(decrypted);\n // Prints: some clear text data\n});\n\nvar encrypted = 'ca981be48e90867604588e75d04feabb63cc007a8f8ad89b10616ed84d815504';\ndecipher.write(encrypted, 'hex');\ndecipher.end();
\nExample: Using Decipher
and piped streams:\n\n
const crypto = require('crypto');\nconst fs = require('fs');\nconst decipher = crypto.createDecipher('aes192', 'a password');\n\nconst input = fs.createReadStream('test.enc');\nconst output = fs.createWriteStream('test.js');\n\ninput.pipe(decipher).pipe(output);
\nExample: Using the [decipher.update()
][] and [decipher.final()
][] methods:\n\n
const crypto = require('crypto');\nconst decipher = crypto.createDecipher('aes192', 'a password');\n\nvar encrypted = 'ca981be48e90867604588e75d04feabb63cc007a8f8ad89b10616ed84d815504';\nvar decrypted = decipher.update(encrypted, 'hex', 'utf8');\ndecrypted += decipher.final('utf8');\nconsole.log(decrypted);\n // Prints: some clear text data
\n",
"methods": [
{
"textRaw": "decipher.final([output_encoding])",
"type": "method",
"name": "final",
"desc": "Returns any remaining deciphered contents. If output_encoding
\nparameter is one of 'binary'
, 'base64'
or 'hex'
, a string is returned.\nIf an output_encoding
is not provided, a [Buffer
][] is returned.\n\n
Once the decipher.final()
method has been called, the Decipher
object can\nno longer be used to decrypt data. Attempts to call decipher.final()
more\nthan once will result in an error being thrown.\n\n
When using an authenticated encryption mode (only GCM
is currently\nsupported), the cipher.setAAD()
method sets the value used for the\nadditional authenticated data (AAD) input parameter.\n\n
When using an authenticated encryption mode (only GCM
is currently\nsupported), the decipher.setAuthTag()
method is used to pass in the\nreceived authentication tag. If no tag is provided, or if the cipher text\nhas been tampered with, [decipher.final()
][] with throw, indicating that the\ncipher text should be discarded due to failed authentication.\n\n
When data has been encrypted without standard block padding, calling\ndecipher.setAutoPadding(false)
will disable automatic padding to prevent\n[decipher.final()
][] from checking for and removing padding.\n\n
Turning auto padding off will only work if the input data's length is a\nmultiple of the ciphers block size.\n\n
\nThe decipher.setAutoPadding()
method must be called before\n[decipher.update()
][].\n\n
Updates the decipher with data
. If the input_encoding
argument is given,\nit's value must be one of 'binary'
, 'base64'
, or 'hex'
and the data
\nargument is a string using the specified encoding. If the input_encoding
\nargument is not given, data
must be a [Buffer
][]. If data
is a\n[Buffer
][] then input_encoding
is ignored.\n\n
The output_encoding
specifies the output format of the enciphered\ndata, and can be 'binary'
, 'ascii'
or 'utf8'
. If the output_encoding
\nis specified, a string using the specified encoding is returned. If no\noutput_encoding
is provided, a [Buffer
][] is returned.\n\n
The decipher.update()
method can be called multiple times with new data until\n[decipher.final()
][] is called. Calling decipher.update()
after\n[decipher.final()
][] will result in an error being thrown.\n\n
The DiffieHellman
class is a utility for creating Diffie-Hellman key\nexchanges.\n\n
Instances of the DiffieHellman
class can be created using the\n[crypto.createDiffieHellman()
][] function.\n\n
const crypto = require('crypto');\nconst assert = require('assert');\n\n// Generate Alice's keys...\nconst alice = crypto.createDiffieHellman(2048);\nconst alice_key = alice.generateKeys();\n\n// Generate Bob's keys...\nconst bob = crypto.createDiffieHellman(alice.getPrime(), alice.getGenerator());\nconst bob_key = bob.generateKeys();\n\n// Exchange and generate the secret...\nconst alice_secret = alice.computeSecret(bob_key);\nconst bob_secret = bob.computeSecret(alice_key);\n\n// OK\nassert.equal(alice_secret.toString('hex'), bob_secret.toString('hex'));
\n",
"methods": [
{
"textRaw": "diffieHellman.computeSecret(other_public_key[, input_encoding][, output_encoding])",
"type": "method",
"name": "computeSecret",
"desc": "Computes the shared secret using other_public_key
as the other\nparty's public key and returns the computed shared secret. The supplied\nkey is interpreted using the specified input_encoding
, and secret is\nencoded using specified output_encoding
. Encodings can be\n'binary'
, 'hex'
, or 'base64'
. If the input_encoding
is not\nprovided, other_public_key
is expected to be a [Buffer
][].\n\n
If output_encoding
is given a string is returned; otherwise, a\n[Buffer
][] is returned.\n\n
Generates private and public Diffie-Hellman key values, and returns\nthe public key in the specified encoding
. This key should be\ntransferred to the other party. Encoding can be 'binary'
, 'hex'
,\nor 'base64'
. If encoding
is provided a string is returned; otherwise a\n[Buffer
][] is returned.\n\n
Returns the Diffie-Hellman generator in the specified encoding
, which can\nbe 'binary'
, 'hex'
, or 'base64'
. If encoding
is provided a string is\nreturned; otherwise a [Buffer
][] is returned.\n\n
Returns the Diffie-Hellman prime in the specified encoding
, which can\nbe 'binary'
, 'hex'
, or 'base64'
. If encoding
is provided a string is\nreturned; otherwise a [Buffer
][] is returned.\n\n
Returns the Diffie-Hellman private key in the specified encoding
,\nwhich can be 'binary'
, 'hex'
, or 'base64'
. If encoding
is provided a\nstring is returned; otherwise a [Buffer
][] is returned.\n\n
Returns the Diffie-Hellman public key in the specified encoding
, which\ncan be 'binary'
, 'hex'
, or 'base64'
. If encoding
is provided a\nstring is returned; otherwise a [Buffer
][] is returned.\n\n
Sets the Diffie-Hellman private key. If the encoding
argument is provided\nand is either 'binary'
, 'hex'
, or 'base64'
, private_key
is expected\nto be a string. If no encoding
is provided, private_key
is expected\nto be a [Buffer
][].\n\n
Sets the Diffie-Hellman public key. If the encoding
argument is provided\nand is either 'binary'
, 'hex'
or 'base64'
, public_key
is expected\nto be a string. If no encoding
is provided, public_key
is expected\nto be a [Buffer
][].\n\n
A bit field containing any warnings and/or errors resulting from a check\nperformed during initialization of the DiffieHellman
object.\n\n
The following values are valid for this property (as defined in constants
\nmodule):\n\n
DH_CHECK_P_NOT_SAFE_PRIME
DH_CHECK_P_NOT_PRIME
DH_UNABLE_TO_CHECK_GENERATOR
DH_NOT_SUITABLE_GENERATOR
The ECDH
class is a utility for creating Elliptic Curve Diffie-Hellman (ECDH)\nkey exchanges.\n\n
Instances of the ECDH
class can be created using the\n[crypto.createECDH()
][] function.\n\n
const crypto = require('crypto');\nconst assert = require('assert');\n\n// Generate Alice's keys...\nconst alice = crypto.createECDH('secp521r1');\nconst alice_key = alice.generateKeys();\n\n// Generate Bob's keys...\nconst bob = crypto.createECDH('secp521r1');\nconst bob_key = bob.generateKeys();\n\n// Exchange and generate the secret...\nconst alice_secret = alice.computeSecret(bob_key);\nconst bob_secret = bob.computeSecret(alice_key);\n\nassert(alice_secret, bob_secret);\n // OK
\n",
"methods": [
{
"textRaw": "ecdh.computeSecret(other_public_key[, input_encoding][, output_encoding])",
"type": "method",
"name": "computeSecret",
"desc": "Computes the shared secret using other_public_key
as the other\nparty's public key and returns the computed shared secret. The supplied\nkey is interpreted using specified input_encoding
, and the returned secret\nis encoded using the specified output_encoding
. Encodings can be\n'binary'
, 'hex'
, or 'base64'
. If the input_encoding
is not\nprovided, other_public_key
is expected to be a [Buffer
][].\n\n
If output_encoding
is given a string will be returned; otherwise a\n[Buffer
][] is returned.\n\n
Generates private and public EC Diffie-Hellman key values, and returns\nthe public key in the specified format
and encoding
. This key should be\ntransferred to the other party.\n\n
The format
arguments specifies point encoding and can be 'compressed'
,\n'uncompressed'
, or 'hybrid'
. If format
is not specified, the point will\nbe returned in 'uncompressed'
format.\n\n
The encoding
argument can be 'binary'
, 'hex'
, or 'base64'
. If\nencoding
is provided a string is returned; otherwise a [Buffer
][]\nis returned.\n\n
Returns the EC Diffie-Hellman private key in the specified encoding
,\nwhich can be 'binary'
, 'hex'
, or 'base64'
. If encoding
is provided\na string is returned; otherwise a [Buffer
][] is returned.\n\n
Returns the EC Diffie-Hellman public key in the specified encoding
and\nformat
.\n\n
The format
argument specifies point encoding and can be 'compressed'
,\n'uncompressed'
, or 'hybrid'
. If format
is not specified the point will be\nreturned in 'uncompressed'
format.\n\n
The encoding
argument can be 'binary'
, 'hex'
, or 'base64'
. If\nencoding
is specified, a string is returned; otherwise a [Buffer
][] is\nreturned.\n\n
Sets the EC Diffie-Hellman private key. The encoding
can be 'binary'
,\n'hex'
or 'base64'
. If encoding
is provided, private_key
is expected\nto be a string; otherwise private_key
is expected to be a [Buffer
][]. If\nprivate_key
is not valid for the curve specified when the ECDH
object was\ncreated, an error is thrown. Upon setting the private key, the associated\npublic point (key) is also generated and set in the ECDH object.\n\n
Sets the EC Diffie-Hellman public key. Key encoding can be 'binary'
,\n'hex'
or 'base64'
. If encoding
is provided public_key
is expected to\nbe a string; otherwise a [Buffer
][] is expected.\n\n
Note that there is not normally a reason to call this method because ECDH
\nonly requires a private key and the other party's public key to compute the\nshared secret. Typically either [ecdh.generateKeys()
][] or\n[ecdh.setPrivateKey()
][] will be called. The [ecdh.setPrivateKey()
][] method\nattempts to generate the public point/key associated with the private key being\nset.\n\n
Example (obtaining a shared secret):\n\n
\nconst crypto = require('crypto');\nconst alice = crypto.createECDH('secp256k1');\nconst bob = crypto.createECDH('secp256k1');\n\n// Note: This is a shortcut way to specify one of Alice's previous private\n// keys. It would be unwise to use such a predictable private key in a real\n// application.\nalice.setPrivateKey(\n crypto.createHash('sha256').update('alice', 'utf8').digest()\n);\n\n// Bob uses a newly generated cryptographically strong\n// pseudorandom key pair bob.generateKeys();\n\nconst alice_secret = alice.computeSecret(bob.getPublicKey(), null, 'hex');\nconst bob_secret = bob.computeSecret(alice.getPublicKey(), null, 'hex');\n\n// alice_secret and bob_secret should be the same shared secret value\nconsole.log(alice_secret === bob_secret);
\n",
"signatures": [
{
"params": [
{
"name": "public_key"
},
{
"name": "encoding",
"optional": true
}
]
}
]
}
]
},
{
"textRaw": "Class: Hash",
"type": "class",
"name": "Hash",
"desc": "The Hash
class is a utility for creating hash digests of data. It can be\nused in one of two ways:\n\n
hash.update()
][] and [hash.digest()
][] methods to produce the\ncomputed hash.The [crypto.createHash()
][] method is used to create Hash
instances. Hash
\nobjects are not to be created directly using the new
keyword.\n\n
Example: Using Hash
objects as streams:\n\n
const crypto = require('crypto');\nconst hash = crypto.createHash('sha256');\n\nhash.on('readable', () => {\n var data = hash.read();\n if (data)\n console.log(data.toString('hex'));\n // Prints:\n // 6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50\n});\n\nhash.write('some data to hash');\nhash.end();
\nExample: Using Hash
and piped streams:\n\n
const crypto = require('crypto');\nconst fs = require('fs');\nconst hash = crypto.createHash('sha256');\n\nconst input = fs.createReadStream('test.js');\ninput.pipe(hash).pipe(process.stdout);
\nExample: Using the [hash.update()
][] and [hash.digest()
][] methods:\n\n
const crypto = require('crypto');\nconst hash = crypto.createHash('sha256');\n\nhash.update('some data to hash');\nconsole.log(hash.digest('hex'));\n // Prints:\n // 6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50
\n",
"methods": [
{
"textRaw": "hash.digest([encoding])",
"type": "method",
"name": "digest",
"desc": "Calculates the digest of all of the data passed to be hashed (using the\n[hash.update()
][] method). The encoding
can be 'hex'
, 'binary'
or\n'base64'
. If encoding
is provided a string will be returned; otherwise\na [Buffer
][] is returned.\n\n
The Hash
object can not be used again after hash.digest()
method has been\ncalled. Multiple calls will cause an error to be thrown.\n\n
Updates the hash content with the given data
, the encoding of which\nis given in input_encoding
and can be 'utf8'
, 'ascii'
or\n'binary'
. If encoding
is not provided, and the data
is a string, an\nencoding of 'utf8'
is enforced. If data
is a [Buffer
][] then\ninput_encoding
is ignored.\n\n
This can be called many times with new data as it is streamed.\n\n
\n", "signatures": [ { "params": [ { "name": "data" }, { "name": "input_encoding", "optional": true } ] } ] } ] }, { "textRaw": "Class: Hmac", "type": "class", "name": "Hmac", "desc": "The Hmac
Class is a utility for creating cryptographic HMAC digests. It can\nbe used in one of two ways:\n\n
hmac.update()
][] and [hmac.digest()
][] methods to produce the\ncomputed HMAC digest.The [crypto.createHmac()
][] method is used to create Hmac
instances. Hmac
\nobjects are not to be created directly using the new
keyword.\n\n
Example: Using Hmac
objects as streams:\n\n
const crypto = require('crypto');\nconst hmac = crypto.createHmac('sha256', 'a secret');\n\nhmac.on('readable', () => {\n var data = hmac.read();\n if (data)\n console.log(data.toString('hex'));\n // Prints:\n // 7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e\n});\n\nhmac.write('some data to hash');\nhmac.end();
\nExample: Using Hmac
and piped streams:\n\n
const crypto = require('crypto');\nconst fs = require('fs');\nconst hmac = crypto.createHmac('sha256', 'a secret');\n\nconst input = fs.createReadStream('test.js');\ninput.pipe(hmac).pipe(process.stdout);
\nExample: Using the [hmac.update()
][] and [hmac.digest()
][] methods:\n\n
const crypto = require('crypto');\nconst hmac = crypto.createHmac('sha256', 'a secret');\n\nhmac.update('some data to hash');\nconsole.log(hmac.digest('hex'));\n // Prints:\n // 7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e
\n",
"methods": [
{
"textRaw": "hmac.digest([encoding])",
"type": "method",
"name": "digest",
"desc": "Calculates the HMAC digest of all of the data passed using [hmac.update()
][].\nThe encoding
can be 'hex'
, 'binary'
or 'base64'
. If encoding
is\nprovided a string is returned; otherwise a [Buffer
][] is returned;\n\n
The Hmac
object can not be used again after hmac.digest()
has been\ncalled. Multiple calls to hmac.digest()
will result in an error being thrown.\n\n
Updates the Hmac
content with the given data
, the encoding of which\nis given in input_encoding
and can be 'utf8'
, 'ascii'
or\n'binary'
. If encoding
is not provided, and the data
is a string, an\nencoding of 'utf8'
is enforced. If data
is a [Buffer
][] then\ninput_encoding
is ignored.\n\n
This can be called many times with new data as it is streamed.\n\n
\n", "signatures": [ { "params": [ { "name": "data" }, { "name": "input_encoding", "optional": true } ] } ] } ] }, { "textRaw": "Class: Sign", "type": "class", "name": "Sign", "desc": "The Sign
Class is a utility for generating signatures. It can be used in one\nof two ways:\n\n
sign.sign()
][] method is used to generate and return the signature, orsign.update()
][] and [sign.sign()
][] methods to produce the\nsignature.The [crypto.createSign()
][] method is used to create Sign
instances. Sign
\nobjects are not to be created directly using the new
keyword.\n\n
Example: Using Sign
objects as streams:\n\n
const crypto = require('crypto');\nconst sign = crypto.createSign('RSA-SHA256');\n\nsign.write('some data to sign');\nsign.end();\n\nconst private_key = getPrivateKeySomehow();\nconsole.log(sign.sign(private_key, 'hex'));\n // Prints the calculated signature
\nExample: Using the [sign.update()
][] and [sign.sign()
][] methods:\n\n
const crypto = require('crypto');\nconst sign = crypto.createSign('RSA-SHA256');\n\nsign.update('some data to sign');\n\nconst private_key = getPrivateKeySomehow();\nconsole.log(sign.sign(private_key, 'hex'));\n // Prints the calculated signature
\nA [sign
][] instance can also be created by just passing in the digest\nalgorithm name, in which case OpenSSL will infer the full signature algorithm\nfrom the type of the PEM-formatted private key, including algorithms that\ndo not have directly exposed name constants, e.g. 'ecdsa-with-SHA256'.\n\n
Example: signing using ECDSA with SHA256\n\n
\nconst crypto = require('crypto');\nconst sign = crypto.createSign('sha256');\n\nsign.update('some data to sign');\n\nconst private_key = '-----BEGIN EC PRIVATE KEY-----\\n' +\n 'MHcCAQEEIF+jnWY1D5kbVYDNvxxo/Y+ku2uJPDwS0r/VuPZQrjjVoAoGCCqGSM49\\n' +\n 'AwEHoUQDQgAEurOxfSxmqIRYzJVagdZfMMSjRNNhB8i3mXyIMq704m2m52FdfKZ2\\n' +\n 'pQhByd5eyj3lgZ7m7jbchtdgyOF8Io/1ng==\\n' +\n '-----END EC PRIVATE KEY-----\\n';\n\nconsole.log(sign.sign(private_key).toString('hex'));
\n",
"methods": [
{
"textRaw": "sign.sign(private_key[, output_format])",
"type": "method",
"name": "sign",
"desc": "Calculates the signature on all the data passed through using either\n[sign.update()
][] or [sign.write()
][stream-writable-write].\n\n
The private_key
argument can be an object or a string. If private_key
is a\nstring, it is treated as a raw key with no passphrase. If private_key
is an\nobject, it is interpreted as a hash containing two properties:\n\n
key
: {String} - PEM encoded private keypassphrase
: {String} - passphrase for the private keyThe output_format
can specify one of 'binary'
, 'hex'
or 'base64'
. If\noutput_format
is provided a string is returned; otherwise a [Buffer
][] is\nreturned.\n\n
The Sign
object can not be again used after sign.sign()
method has been\ncalled. Multiple calls to sign.sign()
will result in an error being thrown.\n\n
Updates the Sign
content with the given data
, the encoding of which\nis given in input_encoding
and can be 'utf8'
, 'ascii'
or\n'binary'
. If encoding
is not provided, and the data
is a string, an\nencoding of 'utf8'
is enforced. If data
is a [Buffer
][] then\ninput_encoding
is ignored.\n\n
This can be called many times with new data as it is streamed.\n\n
\n", "signatures": [ { "params": [ { "name": "data" }, { "name": "input_encoding", "optional": true } ] } ] } ] }, { "textRaw": "Class: Verify", "type": "class", "name": "Verify", "desc": "The Verify
class is a utility for verifying signatures. It can be used in one\nof two ways:\n\n
Using the [verify.update()
][] and [verify.verify()
][] methods to verify\nthe signature.
The [crypto.createSign()
][] method is used to create Sign
instances.\nSign
objects are not to be created directly using the new
keyword.
Example: Using Verify
objects as streams:\n\n
const crypto = require('crypto');\nconst verify = crypto.createVerify('RSA-SHA256');\n\nverify.write('some data to sign');\nverify.end();\n\nconst public_key = getPublicKeySomehow();\nconst signature = getSignatureToVerify();\nconsole.log(sign.verify(public_key, signature));\n // Prints true or false
\nExample: Using the [verify.update()
][] and [verify.verify()
][] methods:\n\n
const crypto = require('crypto');\nconst verify = crypto.createVerify('RSA-SHA256');\n\nverify.update('some data to sign');\n\nconst public_key = getPublicKeySomehow();\nconst signature = getSignatureToVerify();\nconsole.log(verify.verify(public_key, signature));\n // Prints true or false
\n",
"methods": [
{
"textRaw": "verifier.update(data[, input_encoding])",
"type": "method",
"name": "update",
"desc": "Updates the Verify
content with the given data
, the encoding of which\nis given in input_encoding
and can be 'utf8'
, 'ascii'
or\n'binary'
. If encoding
is not provided, and the data
is a string, an\nencoding of 'utf8'
is enforced. If data
is a [Buffer
][] then\ninput_encoding
is ignored.\n\n
This can be called many times with new data as it is streamed.\n\n
\n", "signatures": [ { "params": [ { "name": "data" }, { "name": "input_encoding", "optional": true } ] } ] }, { "textRaw": "verifier.verify(object, signature[, signature_format])", "type": "method", "name": "verify", "desc": "Verifies the provided data using the given object
and signature
.\nThe object
argument is a string containing a PEM encoded object, which can be\none an RSA public key, a DSA public key, or an X.509 certificate.\nThe signature
argument is the previously calculated signature for the data, in\nthe signature_format
which can be 'binary'
, 'hex'
or 'base64'
.\nIf a signature_format
is specified, the signature
is expected to be a\nstring; otherwise signature
is expected to be a [Buffer
][].\n\n
Returns true
or false
depending on the validity of the signature for\nthe data and public key.\n\n
The verifier
object can not be used again after verify.verify()
has been\ncalled. Multiple calls to verify.verify()
will result in an error being\nthrown.\n\n
The dgram
module provides an implementation of UDP Datagram sockets.\n\n
const dgram = require('dgram');\nconst server = dgram.createSocket('udp4');\n\nserver.on('error', (err) => {\n console.log(`server error:\\n${err.stack}`);\n server.close();\n});\n\nserver.on('message', (msg, rinfo) => {\n console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);\n});\n\nserver.on('listening', () => {\n var address = server.address();\n console.log(`server listening ${address.address}:${address.port}`);\n});\n\nserver.bind(41234);\n// server listening 0.0.0.0:41234
\n",
"classes": [
{
"textRaw": "Class: dgram.Socket",
"type": "class",
"name": "dgram.Socket",
"desc": "The dgram.Socket
object is an [EventEmitter
][] that encapsulates the\ndatagram functionality.\n\n
New instances of dgram.Socket
are created using [dgram.createSocket()
][].\nThe new
keyword is not to be used to create dgram.Socket
instances.\n\n
The 'close'
event is emitted after a socket is closed with [close()
][].\nOnce triggered, no new 'message'
events will be emitted on this socket.\n\n
The 'error'
event is emitted whenever any error occurs. The event handler\nfunction is passed a single Error object.\n\n
The 'listening'
event is emitted whenever a socket begins listening for\ndatagram messages. This occurs as soon as UDP sockets are created.\n\n
The 'message'
event is emitted when a new datagram is available on a socket.\nThe event handler function is passed two arguments: msg
and rinfo
. The\nmsg
argument is a [Buffer
][] and rinfo
is an object with the sender's\naddress information provided by the address
, family
and port
properties:\n\n
socket.on('message', (msg, rinfo) => {\n console.log('Received %d bytes from %s:%d\\n',\n msg.length, rinfo.address, rinfo.port);\n});
\n"
}
],
"methods": [
{
"textRaw": "socket.addMembership(multicastAddress[, multicastInterface])",
"type": "method",
"name": "addMembership",
"signatures": [
{
"params": [
{
"textRaw": "`multicastAddress` {String} ",
"name": "multicastAddress",
"type": "String"
},
{
"textRaw": "`multicastInterface` {String}, Optional ",
"name": "multicastInterface",
"type": "String",
"optional": true
}
]
},
{
"params": [
{
"name": "multicastAddress"
},
{
"name": "multicastInterface",
"optional": true
}
]
}
],
"desc": "Tells the kernel to join a multicast group at the given multicastAddress
\nusing the IP_ADD_MEMBERSHIP
socket option. If the multicastInterface
\nargument is not specified, the operating system will try to add membership to\nall valid networking interfaces.\n\n
Returns an object containing the address information for a socket.\nFor UDP sockets, this object will contain address
, family
and port
\nproperties.\n\n
For UDP sockets, causes the dgram.Socket
to listen for datagram messages on a\nnamed port
and optional address
. If port
is not specified, the operating\nsystem will attempt to bind to a random port. If address
is not specified,\nthe operating system will attempt to listen on all addresses. Once binding is\ncomplete, a 'listening'
event is emitted and the optional callback
function\nis called.\n\n
Note that specifying both a 'listening'
event listener and passing a\ncallback
to the socket.bind()
method is not harmful but not very\nuseful.\n\n
A bound datagram socket keeps the Node.js process running to receive\ndatagram messages.\n\n
\nIf binding fails, an 'error'
event is generated. In rare case (e.g.\nattempting to bind with a closed socket), an [Error
][] may be thrown.\n\n
Example of a UDP server listening on port 41234:\n\n
\nconst dgram = require('dgram');\nconst server = dgram.createSocket('udp4');\n\nserver.on('error', (err) => {\n console.log(`server error:\\n${err.stack}`);\n server.close();\n});\n\nserver.on('message', (msg, rinfo) => {\n console.log(`server got: ${msg} from ${rinfo.address}:${rinfo.port}`);\n});\n\nserver.on('listening', () => {\n var address = server.address();\n console.log(`server listening ${address.address}:${address.port}`);\n});\n\nserver.bind(41234);\n// server listening 0.0.0.0:41234
\n"
},
{
"textRaw": "socket.bind(options[, callback])",
"type": "method",
"name": "bind",
"signatures": [
{
"params": [
{
"textRaw": "`options` {Object} - Required. Supports the following properties: ",
"options": [
{
"textRaw": "`port` {Number} - Required. ",
"name": "port",
"type": "Number",
"desc": "Required."
},
{
"textRaw": "`address` {String} - Optional. ",
"name": "address",
"type": "String",
"desc": "Optional."
},
{
"textRaw": "`exclusive` {Boolean} - Optional. ",
"name": "exclusive",
"type": "Boolean",
"desc": "Optional."
}
],
"name": "options",
"type": "Object",
"desc": "Required. Supports the following properties:"
},
{
"textRaw": "`callback` {Function} - Optional. ",
"name": "callback",
"type": "Function",
"desc": "Optional.",
"optional": true
}
]
},
{
"params": [
{
"name": "options"
},
{
"name": "callback",
"optional": true
}
]
}
],
"desc": "For UDP sockets, causes the dgram.Socket
to listen for datagram messages on a\nnamed port
and optional address
that are passed as properties of an\noptions
object passed as the first argument. If port
is not specified, the\noperating system will attempt to bind to a random port. If address
is not\nspecified, the operating system will attempt to listen on all addresses. Once\nbinding is complete, a 'listening'
event is emitted and the optional\ncallback
function is called.\n\n
The options
object may contain an additional exclusive
property that is\nuse when using dgram.Socket
objects with the [cluster
] module. When\nexclusive
is set to false
(the default), cluster workers will use the same\nunderlying socket handle allowing connection handling duties to be shared.\nWhen exclusive
is true
, however, the handle is not shared and attempted\nport sharing results in an error.\n\n
An example socket listening on an exclusive port is shown below.\n\n
\nsocket.bind({\n address: 'localhost',\n port: 8000,\n exclusive: true\n});
\n"
},
{
"textRaw": "socket.close([callback])",
"type": "method",
"name": "close",
"desc": "Close the underlying socket and stop listening for data on it. If a callback is\nprovided, it is added as a listener for the ['close'
][] event.\n\n
Instructs the kernel to leave a multicast group at multicastAddress
using the\nIP_DROP_MEMBERSHIP
socket option. This method is automatically called by the\nkernel when the socket is closed or the process terminates, so most apps will\nnever have reason to call this.\n\n
If multicastInterface
is not specified, the operating system will attempt to\ndrop membership on all valid interfaces.\n\n
Broadcasts a datagram on the socket. The destination port
and address
must\nbe specified.\n\n
The msg
argument contains the message to be sent.\nDepending on its type, different behavior can apply. If msg
is a Buffer
,\nthe offset
and length
specify the offset within the Buffer
where the\nmessage begins and the number of bytes in the message, respectively.\nIf msg
is a String
, then it is automatically converted to a Buffer
\nwith 'utf8'
encoding. With messages that\ncontain multi-byte characters, offset
and length
will be calculated with\nrespect to [byte length][] and not the character position.\nIf msg
is an array, offset
and length
must not be specified.\n\n
The address
argument is a string. If the value of address
is a host name,\nDNS will be used to resolve the address of the host. If the address
is not\nspecified or is an empty string, '127.0.0.1'
or '::1'
will be used instead.\n\n
If the socket has not been previously bound with a call to bind
, the socket\nis assigned a random port number and is bound to the "all interfaces" address\n('0.0.0.0'
for udp4
sockets, '::0'
for udp6
sockets.)\n\n
An optional callback
function may be specified to as a way of reporting\nDNS errors or for determining when it is safe to reuse the buf
object.\nNote that DNS lookups delay the time to send for at least one tick of the\nNode.js event loop.\n\n
The only way to know for sure that the datagram has been sent is by using a\ncallback
. If an error occurs and a callback
is given, the error will be\npassed as the first argument to the callback
. If a callback
is not given,\nthe error is emitted as an 'error'
event on the socket
object.\n\n
Offset and length are optional, but if you specify one you would need to\nspecify the other. Also, they are supported only when the first\nargument is a Buffer
.\n\n
Example of sending a UDP packet to a random port on localhost
;\n\n
const dgram = require('dgram');\nconst message = Buffer.from('Some bytes');\nconst client = dgram.createSocket('udp4');\nclient.send(message, 41234, 'localhost', (err) => {\n client.close();\n});
\nExample of sending a UDP packet composed of multiple buffers to a random port on localhost
;\n\n
const dgram = require('dgram');\nconst buf1 = Buffer.from('Some ');\nconst buf2 = Buffer.from('bytes');\nconst client = dgram.createSocket('udp4');\nclient.send([buf1, buf2], 41234, 'localhost', (err) => {\n client.close();\n});
\nSending multiple buffers might be faster or slower depending on your\napplication and operating system: benchmark it. Usually it is faster.\n\n
\nA Note about UDP datagram size\n\n
\nThe maximum size of an IPv4/v6
datagram depends on the MTU
\n(Maximum Transmission Unit) and on the Payload Length
field size.\n\n
The Payload Length
field is 16 bits
wide, which means that a normal\npayload exceed 64K octets including the internet header and data\n(65,507 bytes = 65,535 − 8 bytes UDP header − 20 bytes IP header);\nthis is generally true for loopback interfaces, but such long datagram\nmessages are impractical for most hosts and networks.
The MTU
is the largest size a given link layer technology can support for\ndatagram messages. For any link, IPv4
mandates a minimum MTU
of 68
\noctets, while the recommended MTU
for IPv4 is 576
(typically recommended\nas the MTU
for dial-up type applications), whether they arrive whole or in\nfragments.
For IPv6
, the minimum MTU
is 1280
octets, however, the mandatory minimum\nfragment reassembly buffer size is 1500
octets. The value of 68
octets is\nvery small, since most current link layer technologies, like Ethernet, have a\nminimum MTU
of 1500
.
It is impossible to know in advance the MTU of each link through which\na packet might travel. Sending a datagram greater than the receiver MTU
will\nnot work because the packet will get silently dropped without informing the\nsource that the data did not reach its intended recipient.\n\n
Sets or clears the SO_BROADCAST
socket option. When set to true
, UDP\npackets may be sent to a local interface's broadcast address.\n\n
Sets or clears the IP_MULTICAST_LOOP
socket option. When set to true
,\nmulticast packets will also be received on the local interface.\n\n
Sets the IP_MULTICAST_TTL
socket option. While TTL generally stands for\n"Time to Live", in this context it specifies the number of IP hops that a\npacket is allowed to travel through, specifically for multicast traffic. Each\nrouter or gateway that forwards a packet decrements the TTL. If the TTL is\ndecremented to 0 by a router, it will not be forwarded.\n\n
The argument passed to to socket.setMulticastTTL()
is a number of hops\nbetween 0 and 255. The default on most systems is 1
but can vary.\n\n
Sets the IP_TTL
socket option. While TTL generally stands for "Time to Live",\nin this context it specifies the number of IP hops that a packet is allowed to\ntravel through. Each router or gateway that forwards a packet decrements the\nTTL. If the TTL is decremented to 0 by a router, it will not be forwarded.\nChanging TTL values is typically done for network probes or when multicasting.\n\n
The argument to socket.setTTL()
is a number of hops between 1 and 255.\nThe default on most systems is 64 but can vary.\n\n
By default, binding a socket will cause it to block the Node.js process from\nexiting as long as the socket is open. The socket.unref()
method can be used\nto exclude the socket from the reference counting that keeps the Node.js\nprocess active. The socket.ref()
method adds the socket back to the reference\ncounting and restores the default behavior.\n\n
Calling socket.ref()
multiples times will have no additional effect.\n\n
The socket.ref()
method returns a reference to the socket so calls can be\nchained.\n\n
By default, binding a socket will cause it to block the Node.js process from\nexiting as long as the socket is open. The socket.unref()
method can be used\nto exclude the socket from the reference counting that keeps the Node.js\nprocess active, allowing the process to exit even if the socket is still\nlistening.\n\n
Calling socket.unref()
multiple times will have no addition effect.\n\n
The socket.unref()
method returns a reference to the socket so calls can be\nchained.\n\n
As of Node.js v0.10, [dgram.Socket#bind()
][] changed to an asynchronous\nexecution model. Legacy code that assumes synchronous behavior, as in the\nfollowing example:\n\n
const s = dgram.createSocket('udp4');\ns.bind(1234);\ns.addMembership('224.0.0.114');
\nMust be changed to pass a callback function to the [dgram.Socket#bind()
][]\nfunction:\n\n
const s = dgram.createSocket('udp4');\ns.bind(1234, () => {\n s.addMembership('224.0.0.114');\n});
\n",
"type": "module",
"displayName": "Change to asynchronous `socket.bind()` behavior"
}
]
}
],
"modules": [
{
"textRaw": "`dgram` module functions",
"name": "`dgram`_module_functions",
"methods": [
{
"textRaw": "dgram.createSocket(options[, callback])",
"type": "method",
"name": "createSocket",
"signatures": [
{
"return": {
"textRaw": "Returns: {dgram.Socket} ",
"name": "return",
"type": "dgram.Socket"
},
"params": [
{
"textRaw": "`options` {Object} ",
"name": "options",
"type": "Object"
},
{
"textRaw": "`callback` {Function} Attached as a listener to `'message'` events. ",
"name": "callback",
"type": "Function",
"desc": "Attached as a listener to `'message'` events.",
"optional": true
}
]
},
{
"params": [
{
"name": "options"
},
{
"name": "callback",
"optional": true
}
]
}
],
"desc": "Creates a dgram.Socket
object. The options
argument is an object that\nshould contain a type
field of either udp4
or udp6
and an optional\nboolean reuseAddr
field.\n\n
When reuseAddr
is true
[socket.bind()
][] will reuse the address, even if\nanother process has already bound a socket on it. reuseAddr
defaults to\nfalse
. An optional callback
function can be passed specified which is added\nas a listener for 'message'
events.\n\n
Once the socket is created, calling [socket.bind()
][] will instruct the\nsocket to begin listening for datagram messages. When address
and port
are\nnot passed to [socket.bind()
][] the method will bind the socket to the "all\ninterfaces" address on a random port (it does the right thing for both udp4
\nand udp6
sockets). The bound address and port can be retrieved using\n[socket.address().address
][] and [socket.address().port
][].\n\n
Creates a dgram.Socket
object of the specified type
. The type
argument\ncan be either udp4
or udp6
. An optional callback
function can be passed\nwhich is added as a listener for 'message'
events.\n\n
Once the socket is created, calling [socket.bind()
][] will instruct the\nsocket to begin listening for datagram messages. When address
and port
are\nnot passed to [socket.bind()
][] the method will bind the socket to the "all\ninterfaces" address on a random port (it does the right thing for both udp4
\nand udp6
sockets). The bound address and port can be retrieved using\n[socket.address().address
][] and [socket.address().port
][].\n\n
The dns
module contains functions belonging to two different categories:\n\n
1) Functions that use the underlying operating system facilities to perform\nname resolution, and that do not necessarily perform any network communication.\nThis category contains only one function: [dns.lookup()
][]. Developers\nlooking to perform name resolution in the same way that other applications on\nthe same operating system behave should use [dns.lookup()
][].\n\n
For example, looking up nodejs.org
.\n\n
const dns = require('dns');\n\ndns.lookup('nodejs.org', (err, addresses, family) => {\n console.log('addresses:', addresses);\n});
\n2) Functions that connect to an actual DNS server to perform name resolution,\nand that always use the network to perform DNS queries. This category\ncontains all functions in the dns
module except [dns.lookup()
][]. These\nfunctions do not use the same set of configuration files used by\n[dns.lookup()
][] (e.g. /etc/hosts
). These functions should be used by\ndevelopers who do not want to use the underlying operating system's facilities\nfor name resolution, and instead want to always perform DNS queries.\n\n
Below is an example that resolves 'nodejs.org'
then reverse resolves the IP\naddresses that are returned.\n\n
const dns = require('dns');\n\ndns.resolve4('nodejs.org', (err, addresses) => {\n if (err) throw err;\n\n console.log(`addresses: ${JSON.stringify(addresses)}`);\n\n addresses.forEach((a) => {\n dns.reverse(a, (err, hostnames) => {\n if (err) {\n throw err;\n }\n console.log(`reverse for ${a}: ${JSON.stringify(hostnames)}`);\n });\n });\n});
\nThere are subtle consequences in choosing one over the other, please consult\nthe [Implementation considerations section][] for more information.\n\n
\n", "methods": [ { "textRaw": "dns.getServers()", "type": "method", "name": "getServers", "desc": "Returns an array of IP address strings that are being used for name\nresolution.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "dns.lookup(hostname[, options], callback)", "type": "method", "name": "lookup", "desc": "Resolves a hostname (e.g. 'nodejs.org'
) into the first found A (IPv4) or\nAAAA (IPv6) record. options
can be an object or integer. If options
is\nnot provided, then IPv4 and IPv6 addresses are both valid. If options
is\nan integer, then it must be 4
or 6
.\n\n
Alternatively, options
can be an object containing these properties:\n\n
family
{Number} - The record family. If present, must be the integer\n4
or 6
. If not provided, both IP v4 and v6 addresses are accepted.hints
: {Number} - If present, it should be one or more of the supported\ngetaddrinfo
flags. If hints
is not provided, then no flags are passed to\ngetaddrinfo
. Multiple flags can be passed through hints
by logically\nOR
ing their values.\nSee [supported getaddrinfo
flags][] for more information on supported\nflags.all
: {Boolean} - When true
, the callback returns all resolved addresses\nin an array, otherwise returns a single address. Defaults to false
.All properties are optional. An example usage of options is shown below.\n\n
\n{\n family: 4,\n hints: dns.ADDRCONFIG | dns.V4MAPPED,\n all: false\n}
\nThe callback
function has arguments (err, address, family)
. address
is a\nstring representation of an IPv4 or IPv6 address. family
is either the\ninteger 4
or 6
and denotes the family of address
(not necessarily the\nvalue initially passed to lookup
).\n\n
With the all
option set to true
, the arguments change to\n(err, addresses)
, with addresses
being an array of objects with the\nproperties address
and family
.\n\n
On error, err
is an [Error
][] object, where err.code
is the error code.\nKeep in mind that err.code
will be set to 'ENOENT'
not only when\nthe hostname does not exist but also when the lookup fails in other ways\nsuch as no available file descriptors.\n\n
dns.lookup()
does not necessarily have anything to do with the DNS protocol.\nThe implementation uses an operating system facility that can associate names\nwith addresses, and vice versa. This implementation can have subtle but\nimportant consequences on the behavior of any Node.js program. Please take some\ntime to consult the [Implementation considerations section][] before using\ndns.lookup()
.\n\n
The following flags can be passed as hints to [dns.lookup()
][].\n\n
dns.ADDRCONFIG
: Returned address types are determined by the types\nof addresses supported by the current system. For example, IPv4 addresses\nare only returned if the current system has at least one IPv4 address\nconfigured. Loopback addresses are not considered.dns.V4MAPPED
: If the IPv6 family was specified, but no IPv6 addresses were\nfound, then return IPv4 mapped IPv6 addresses. Note that it is not supported\non some operating systems (e.g FreeBSD 10.1).Resolves the given address
and port
into a hostname and service using\nthe operating system's underlying getnameinfo
implementation.\n\n
If address
is not a valid IP address, a TypeError
will be thrown.\nThe port
will be coerced to a number. If it is not a legal port, a TypeError
\nwill be thrown.\n\n
The callback has arguments (err, hostname, service)
. The hostname
and\nservice
arguments are strings (e.g. 'localhost'
and 'http'
respectively).\n\n
On error, err
is an [Error
][] object, where err.code
is the error code.\n\n
const dns = require('dns');\ndns.lookupService('127.0.0.1', 22, (err, hostname, service) => {\n console.log(hostname, service);\n // Prints: localhost ssh\n});
\n",
"signatures": [
{
"params": [
{
"name": "address"
},
{
"name": "port"
},
{
"name": "callback"
}
]
}
]
},
{
"textRaw": "dns.resolve(hostname[, rrtype], callback)",
"type": "method",
"name": "resolve",
"desc": "Uses the DNS protocol to resolve a hostname (e.g. 'nodejs.org'
) into an\narray of the record types specified by rrtype
.\n\n
Valid values for rrtype
are:\n\n
'A'
- IPV4 addresses, default'AAAA'
- IPV6 addresses'MX'
- mail exchange records'TXT'
- text records'SRV'
- SRV records'PTR'
- PTR records'NS'
- name server records'CNAME'
- canonical name records'SOA'
- start of authority recordThe callback
function has arguments (err, addresses)
. When successful,\naddresses
will be an array. The type of each item in addresses
is\ndetermined by the record type, and described in the documentation for the\ncorresponding lookup methods.\n\n
On error, err
is an [Error
][] object, where err.code
is\none of the error codes listed here.\n\n
Uses the DNS protocol to resolve a IPv4 addresses (A
records) for the\nhostname
. The addresses
argument passed to the callback
function\nwill contain an array of IPv4 addresses (e.g.\n['74.125.79.104', '74.125.79.105', '74.125.79.106']
).\n\n
Uses the DNS protocol to resolve a IPv6 addresses (AAAA
records) for the\nhostname
. The addresses
argument passed to the callback
function\nwill contain an array of IPv6 addresses.\n\n
Uses the DNS protocol to resolve CNAME
records for the hostname
. The\naddresses
argument passed to the callback
function\nwill contain an array of canonical name records available for the hostname
\n(e.g. ['bar.example.com']
).\n\n
Uses the DNS protocol to resolve mail exchange records (MX
records) for the\nhostname
. The addresses
argument passed to the callback
function will\ncontain an array of objects containing both a priority
and exchange
\nproperty (e.g. [{priority: 10, exchange: 'mx.example.com'}, ...]
).\n\n
Uses the DNS protocol to resolve name server records (NS
records) for the\nhostname
. The addresses
argument passed to the callback
function will\ncontain an array of name server records available for hostname
\n(e.g., ['ns1.example.com', 'ns2.example.com']
).\n\n
Uses the DNS protocol to resolve a start of authority record (SOA
record) for\nthe hostname
. The addresses
argument passed to the callback
function will\nbe an object with the following properties:\n\n
nsname
hostmaster
serial
refresh
retry
expire
minttl
{\n nsname: 'ns.example.com',\n hostmaster: 'root.example.com',\n serial: 2013101809,\n refresh: 10000,\n retry: 2400,\n expire: 604800,\n minttl: 3600\n}
\n",
"signatures": [
{
"params": [
{
"name": "hostname"
},
{
"name": "callback"
}
]
}
]
},
{
"textRaw": "dns.resolveSrv(hostname, callback)",
"type": "method",
"name": "resolveSrv",
"desc": "Uses the DNS protocol to resolve service records (SRV
records) for the\nhostname
. The addresses
argument passed to the callback
function will\nbe an array of objects with the following properties:\n\n
priority
weight
port
name
{\n priority: 10,\n weight: 5,\n port: 21223,\n name: 'service.example.com'\n}
\n",
"signatures": [
{
"params": [
{
"name": "hostname"
},
{
"name": "callback"
}
]
}
]
},
{
"textRaw": "dns.resolvePtr(hostname, callback)",
"type": "method",
"name": "resolvePtr",
"desc": "Uses the DNS protocol to resolve pointer records (PTR
records) for the\nhostname
. The addresses
argument passed to the callback
function will\nbe an array of strings containing the reply records.\n\n
Uses the DNS protocol to resolve text queries (TXT
records) for the\nhostname
. The addresses
argument passed to the callback
function is\nis a two-dimentional array of the text records available for hostname
(e.g.,\n[ ['v=spf1 ip4:0.0.0.0 ', '~all' ] ]
). Each sub-array contains TXT chunks of\none record. Depending on the use case, these could be either joined together or\ntreated separately.\n\n
Performs a reverse DNS query that resolves an IPv4 or IPv6 address to an\narray of hostnames.\n\n
\nThe callback
function has arguments (err, hostnames)
, where hostnames
\nis an array of resolved hostnames for the given ip
.\n\n
On error, err
is an [Error
][] object, where err.code
is\none of the [DNS error codes][].\n\n
Sets the IP addresses of the servers to be used when resolving. The servers
\nargument is an array of IPv4 or IPv6 addresses.\n\n
If a port specified on the address it will be removed.\n\n
\nAn error will be thrown if an invalid address is provided.\n\n
\nThe dns.setServers()
method must not be called while a DNS query is in\nprogress.\n\n
Each DNS query can return one of the following error codes:\n\n
\ndns.NODATA
: DNS server returned answer with no data.dns.FORMERR
: DNS server claims query was misformatted.dns.SERVFAIL
: DNS server returned general failure.dns.NOTFOUND
: Domain name not found.dns.NOTIMP
: DNS server does not implement requested operation.dns.REFUSED
: DNS server refused query.dns.BADQUERY
: Misformatted DNS query.dns.BADNAME
: Misformatted hostname.dns.BADFAMILY
: Unsupported address family.dns.BADRESP
: Misformatted DNS reply.dns.CONNREFUSED
: Could not contact DNS servers.dns.TIMEOUT
: Timeout while contacting DNS servers.dns.EOF
: End of file.dns.FILE
: Error reading file.dns.NOMEM
: Out of memory.dns.DESTRUCTION
: Channel is being destroyed.dns.BADSTR
: Misformatted string.dns.BADFLAGS
: Illegal flags specified.dns.NONAME
: Given hostname is not numeric.dns.BADHINTS
: Illegal hints flags specified.dns.NOTINITIALIZED
: c-ares library initialization not yet performed.dns.LOADIPHLPAPI
: Error loading iphlpapi.dll.dns.ADDRGETNETWORKPARAMS
: Could not find GetNetworkParams function.dns.CANCELLED
: DNS query cancelled.Although [dns.lookup()
][] and the various dns.resolve*()/dns.reverse()
\nfunctions have the same goal of associating a network name with a network\naddress (or vice versa), their behavior is quite different. These differences\ncan have subtle but significant consequences on the behavior of Node.js\nprograms.\n\n
Under the hood, [dns.lookup()
][] uses the same operating system facilities\nas most other programs. For instance, [dns.lookup()
][] will almost always\nresolve a given name the same way as the ping
command. On most POSIX-like\noperating systems, the behavior of the [dns.lookup()
][] function can be\nmodified by changing settings in nsswitch.conf(5)
and/or resolv.conf(5)
,\nbut note that changing these files will change the behavior of all other\nprograms running on the same operating system.\n\n
Though the call to dns.lookup()
will be asynchronous from JavaScript's\nperspective, it is implemented as a synchronous call to getaddrinfo(3)
that\nruns on libuv's threadpool. Because libuv's threadpool has a fixed size, it\nmeans that if for whatever reason the call to getaddrinfo(3)
takes a long\ntime, other operations that could run on libuv's threadpool (such as filesystem\noperations) will experience degraded performance. In order to mitigate this\nissue, one potential solution is to increase the size of libuv's threadpool by\nsetting the 'UV_THREADPOOL_SIZE'
environment variable to a value greater than\n4
(its current default value). For more information on libuv's threadpool, see\n[the official libuv documentation][].\n\n
These functions are implemented quite differently than [dns.lookup()
][]. They\ndo not use getaddrinfo(3)
and they always perform a DNS query on the\nnetwork. This network communication is always done asynchronously, and does not\nuse libuv's threadpool.\n\n
As a result, these functions cannot have the same negative impact on other\nprocessing that happens on libuv's threadpool that [dns.lookup()
][] can have.\n\n
They do not use the same set of configuration files than what [dns.lookup()
][]\nuses. For instance, they do not use the configuration from /etc/hosts
.\n\n
This module is pending deprecation. Once a replacement API has been\nfinalized, this module will be fully deprecated. Most end users should\nnot have cause to use this module. Users who absolutely must have\nthe functionality that domains provide may rely on it for the time being\nbut should expect to have to migrate to a different solution\nin the future.\n\n
\nDomains provide a way to handle multiple different IO operations as a\nsingle group. If any of the event emitters or callbacks registered to a\ndomain emit an 'error'
event, or throw an error, then the domain object\nwill be notified, rather than losing the context of the error in the\nprocess.on('uncaughtException')
handler, or causing the program to\nexit immediately with an error code.\n\n
Domain error handlers are not a substitute for closing down your\nprocess when an error occurs.\n\n
\nBy the very nature of how [throw
][] works in JavaScript, there is almost\nnever any way to safely "pick up where you left off", without leaking\nreferences, or creating some other sort of undefined brittle state.\n\n
The safest way to respond to a thrown error is to shut down the\nprocess. Of course, in a normal web server, you might have many\nconnections open, and it is not reasonable to abruptly shut those down\nbecause an error was triggered by someone else.\n\n
\nThe better approach is to send an error response to the request that\ntriggered the error, while letting the others finish in their normal\ntime, and stop listening for new requests in that worker.\n\n
\nIn this way, domain
usage goes hand-in-hand with the cluster module,\nsince the master process can fork a new worker when a worker\nencounters an error. For Node.js programs that scale to multiple\nmachines, the terminating proxy or service registry can take note of\nthe failure, and react accordingly.\n\n
For example, this is not a good idea:\n\n
\n// XXX WARNING! BAD IDEA!\n\nvar d = require('domain').create();\nd.on('error', (er) => {\n // The error won't crash the process, but what it does is worse!\n // Though we've prevented abrupt process restarting, we are leaking\n // resources like crazy if this ever happens.\n // This is no better than process.on('uncaughtException')!\n console.log('error, but oh well', er.message);\n});\nd.run(() => {\n require('http').createServer((req, res) => {\n handleRequest(req, res);\n }).listen(PORT);\n});
\nBy using the context of a domain, and the resilience of separating our\nprogram into multiple worker processes, we can react more\nappropriately, and handle errors with much greater safety.\n\n
\n// Much better!\n\nconst cluster = require('cluster');\nconst PORT = +process.env.PORT || 1337;\n\nif (cluster.isMaster) {\n // In real life, you'd probably use more than just 2 workers,\n // and perhaps not put the master and worker in the same file.\n //\n // You can also of course get a bit fancier about logging, and\n // implement whatever custom logic you need to prevent DoS\n // attacks and other bad behavior.\n //\n // See the options in the cluster documentation.\n //\n // The important thing is that the master does very little,\n // increasing our resilience to unexpected errors.\n\n cluster.fork();\n cluster.fork();\n\n cluster.on('disconnect', (worker) => {\n console.error('disconnect!');\n cluster.fork();\n });\n\n} else {\n // the worker\n //\n // This is where we put our bugs!\n\n const domain = require('domain');\n\n // See the cluster documentation for more details about using\n // worker processes to serve requests. How it works, caveats, etc.\n\n const server = require('http').createServer((req, res) => {\n var d = domain.create();\n d.on('error', (er) => {\n console.error('error', er.stack);\n\n // Note: we're in dangerous territory!\n // By definition, something unexpected occurred,\n // which we probably didn't want.\n // Anything can happen now! Be very careful!\n\n try {\n // make sure we close down within 30 seconds\n var killtimer = setTimeout(() => {\n process.exit(1);\n }, 30000);\n // But don't keep the process open just for that!\n killtimer.unref();\n\n // stop taking new requests.\n server.close();\n\n // Let the master know we're dead. This will trigger a\n // 'disconnect' in the cluster master, and then it will fork\n // a new worker.\n cluster.worker.disconnect();\n\n // try to send an error to the request that triggered the problem\n res.statusCode = 500;\n res.setHeader('content-type', 'text/plain');\n res.end('Oops, there was a problem!\\n');\n } catch (er2) {\n // oh well, not much we can do at this point.\n console.error('Error sending 500!', er2.stack);\n }\n });\n\n // Because req and res were created before this domain existed,\n // we need to explicitly add them.\n // See the explanation of implicit vs explicit binding below.\n d.add(req);\n d.add(res);\n\n // Now run the handler function in the domain.\n d.run(() => {\n handleRequest(req, res);\n });\n });\n server.listen(PORT);\n}\n\n// This part isn't important. Just an example routing thing.\n// You'd put your fancy application logic here.\nfunction handleRequest(req, res) {\n switch(req.url) {\n case '/error':\n // We do some async stuff, and then...\n setTimeout(() => {\n // Whoops!\n flerb.bark();\n });\n break;\n default:\n res.end('ok');\n }\n}
\n"
},
{
"textRaw": "Additions to Error objects",
"name": "Additions to Error objects",
"type": "misc",
"desc": "Any time an Error
object is routed through a domain, a few extra fields\nare added to it.\n\n
error.domain
The domain that first handled the error.error.domainEmitter
The event emitter that emitted an 'error'
event\nwith the error object.error.domainBound
The callback function which was bound to the\ndomain, and passed an error as its first argument.error.domainThrown
A boolean indicating whether the error was\nthrown, emitted, or passed to a bound callback function.If domains are in use, then all new EventEmitter objects (including\nStream objects, requests, responses, etc.) will be implicitly bound to\nthe active domain at the time of their creation.\n\n
\nAdditionally, callbacks passed to lowlevel event loop requests (such as\nto fs.open, or other callback-taking methods) will automatically be\nbound to the active domain. If they throw, then the domain will catch\nthe error.\n\n
\nIn order to prevent excessive memory usage, Domain objects themselves\nare not implicitly added as children of the active domain. If they\nwere, then it would be too easy to prevent request and response objects\nfrom being properly garbage collected.\n\n
\nIf you want to nest Domain objects as children of a parent Domain,\nthen you must explicitly add them.\n\n
\nImplicit binding routes thrown errors and 'error'
events to the\nDomain's 'error'
event, but does not register the EventEmitter on the\nDomain, so [domain.dispose()
][] will not shut down the EventEmitter.\nImplicit binding only takes care of thrown errors and 'error'
events.\n\n
Sometimes, the domain in use is not the one that ought to be used for a\nspecific event emitter. Or, the event emitter could have been created\nin the context of one domain, but ought to instead be bound to some\nother domain.\n\n
\nFor example, there could be one domain in use for an HTTP server, but\nperhaps we would like to have a separate domain to use for each request.\n\n
\nThat is possible via explicit binding.\n\n
\nFor example:\n\n
\n// create a top-level domain for the server\nconst domain = require('domain');\nconst http = require('http');\nconst serverDomain = domain.create();\n\nserverDomain.run(() => {\n // server is created in the scope of serverDomain\n http.createServer((req, res) => {\n // req and res are also created in the scope of serverDomain\n // however, we'd prefer to have a separate domain for each request.\n // create it first thing, and add req and res to it.\n var reqd = domain.create();\n reqd.add(req);\n reqd.add(res);\n reqd.on('error', (er) => {\n console.error('Error', er, req.url);\n try {\n res.writeHead(500);\n res.end('Error occurred, sorry.');\n } catch (er) {\n console.error('Error sending 500', er, req.url);\n }\n });\n }).listen(1337);\n});
\n"
}
],
"methods": [
{
"textRaw": "domain.create()",
"type": "method",
"name": "create",
"signatures": [
{
"return": {
"textRaw": "return: {Domain} ",
"name": "return",
"type": "Domain"
},
"params": []
},
{
"params": []
}
],
"desc": "Returns a new Domain object.\n\n
\n" } ], "classes": [ { "textRaw": "Class: Domain", "type": "class", "name": "Domain", "desc": "The Domain class encapsulates the functionality of routing errors and\nuncaught exceptions to the active Domain object.\n\n
\nDomain is a child class of [EventEmitter
][]. To handle the errors that it\ncatches, listen to its 'error'
event.\n\n
Run the supplied function in the context of the domain, implicitly\nbinding all event emitters, timers, and lowlevel requests that are\ncreated in that context. Optionally, arguments can be passed to\nthe function.\n\n
\nThis is the most basic way to use a domain.\n\n
\nExample:\n\n
\nconst domain = require('domain');\nconst fs = require('fs');\nconst d = domain.create();\nd.on('error', (er) => {\n console.error('Caught error!', er);\n});\nd.run(() => {\n process.nextTick(() => {\n setTimeout(() => { // simulating some various async stuff\n fs.open('non-existent file', 'r', (er, fd) => {\n if (er) throw er;\n // proceed...\n });\n }, 100);\n });\n});
\nIn this example, the d.on('error')
handler will be triggered, rather\nthan crashing the program.\n\n
Explicitly adds an emitter to the domain. If any event handlers called by\nthe emitter throw an error, or if the emitter emits an 'error'
event, it\nwill be routed to the domain's 'error'
event, just like with implicit\nbinding.\n\n
This also works with timers that are returned from [setInterval()
][] and\n[setTimeout()
][]. If their callback function throws, it will be caught by\nthe domain 'error' handler.\n\n
If the Timer or EventEmitter was already bound to a domain, it is removed\nfrom that one, and bound to this one instead.\n\n
\n" }, { "textRaw": "domain.remove(emitter)", "type": "method", "name": "remove", "signatures": [ { "params": [ { "textRaw": "`emitter` {EventEmitter|Timer} emitter or timer to be removed from the domain ", "name": "emitter", "type": "EventEmitter|Timer", "desc": "emitter or timer to be removed from the domain" } ] }, { "params": [ { "name": "emitter" } ] } ], "desc": "The opposite of [domain.add(emitter)
][]. Removes domain handling from the\nspecified emitter.\n\n
The returned function will be a wrapper around the supplied callback\nfunction. When the returned function is called, any errors that are\nthrown will be routed to the domain's 'error'
event.\n\n
const d = domain.create();\n\nfunction readSomeFile(filename, cb) {\n fs.readFile(filename, 'utf8', d.bind((er, data) => {\n // if this throws, it will also be passed to the domain\n return cb(er, data ? JSON.parse(data) : null);\n }));\n}\n\nd.on('error', (er) => {\n // an error occurred somewhere.\n // if we throw it now, it will crash the program\n // with the normal line number and stack message.\n});
\n"
},
{
"textRaw": "domain.intercept(callback)",
"type": "method",
"name": "intercept",
"signatures": [
{
"return": {
"textRaw": "return: {Function} The intercepted function ",
"name": "return",
"type": "Function",
"desc": "The intercepted function"
},
"params": [
{
"textRaw": "`callback` {Function} The callback function ",
"name": "callback",
"type": "Function",
"desc": "The callback function"
}
]
},
{
"params": [
{
"name": "callback"
}
]
}
],
"desc": "This method is almost identical to [domain.bind(callback)
][]. However, in\naddition to catching thrown errors, it will also intercept [Error
][]\nobjects sent as the first argument to the function.\n\n
In this way, the common if (err) return callback(err);
pattern can be replaced\nwith a single error handler in a single place.\n\n
const d = domain.create();\n\nfunction readSomeFile(filename, cb) {\n fs.readFile(filename, 'utf8', d.intercept((data) => {\n // note, the first argument is never passed to the\n // callback since it is assumed to be the 'Error' argument\n // and thus intercepted by the domain.\n\n // if this throws, it will also be passed to the domain\n // so the error-handling logic can be moved to the 'error'\n // event on the domain instead of being repeated throughout\n // the program.\n return cb(null, JSON.parse(data));\n }));\n}\n\nd.on('error', (er) => {\n // an error occurred somewhere.\n // if we throw it now, it will crash the program\n // with the normal line number and stack message.\n});
\n"
},
{
"textRaw": "domain.enter()",
"type": "method",
"name": "enter",
"desc": "The enter
method is plumbing used by the run
, bind
, and intercept
\nmethods to set the active domain. It sets domain.active
and process.domain
\nto the domain, and implicitly pushes the domain onto the domain stack managed\nby the domain module (see [domain.exit()
][] for details on the domain stack). The\ncall to enter
delimits the beginning of a chain of asynchronous calls and I/O\noperations bound to a domain.\n\n
Calling enter
changes only the active domain, and does not alter the domain\nitself. enter
and exit
can be called an arbitrary number of times on a\nsingle domain.\n\n
If the domain on which enter
is called has been disposed, enter
will return\nwithout setting the domain.\n\n
The exit
method exits the current domain, popping it off the domain stack.\nAny time execution is going to switch to the context of a different chain of\nasynchronous calls, it's important to ensure that the current domain is exited.\nThe call to exit
delimits either the end of or an interruption to the chain\nof asynchronous calls and I/O operations bound to a domain.\n\n
If there are multiple, nested domains bound to the current execution context,\nexit
will exit any domains nested within this domain.\n\n
Calling exit
changes only the active domain, and does not alter the domain\nitself. enter
and exit
can be called an arbitrary number of times on a\nsingle domain.\n\n
If the domain on which exit
is called has been disposed, exit
will return\nwithout exiting the domain.\n\n
Stability: 0 - Deprecated. Please recover from failed IO actions\nexplicitly via error event handlers set on the domain.
\nOnce dispose
has been called, the domain will no longer be used by callbacks\nbound into the domain via run
, bind
, or intercept
, and a 'dispose'
event\nis emitted.\n\n
An array of timers and event emitters that have been explicitly added\nto the domain.\n\n
\n" } ] } ], "type": "module", "displayName": "Domain" }, { "textRaw": "Events", "name": "Events", "stability": 2, "stabilityText": "Stable", "type": "module", "desc": "Much of the Node.js core API is built around an idiomatic asynchronous\nevent-driven architecture in which certain kinds of objects (called "emitters")\nperiodically emit named events that cause Function objects ("listeners") to be\ncalled.\n\n
\nFor instance: a [net.Server
][] object emits an event each time a peer\nconnects to it; a [fs.ReadStream
][] emits an event when the file is opened;\na [stream][] emits an event whenever data is available to be read.\n\n
All objects that emit events are instances of the EventEmitter
class. These\nobjects expose an eventEmitter.on()
function that allows one or more\nFunctions to be attached to named events emitted by the object. Typically,\nevent names are camel-cased strings but any valid JavaScript property key\ncan be used.\n\n
When the EventEmitter
object emits an event, all of the Functions attached\nto that specific event are called synchronously. Any values returned by the\ncalled listeners are ignored and will be discarded.\n\n
The following example shows a simple EventEmitter
instance with a single\nlistener. The eventEmitter.on()
method is used to register listeners, while\nthe eventEmitter.emit()
method is used to trigger the event.\n\n
const EventEmitter = require('events');\nconst util = require('util');\n\nfunction MyEmitter() {\n EventEmitter.call(this);\n}\nutil.inherits(MyEmitter, EventEmitter);\n\nconst myEmitter = new MyEmitter();\nmyEmitter.on('event', () => {\n console.log('an event occurred!');\n});\nmyEmitter.emit('event');
\nAny object can become an EventEmitter
through inheritance. The example above\nuses the traditional Node.js style prototypical inheritance using\nthe util.inherits()
method. It is, however, possible to use ES6 classes as\nwell:\n\n
const EventEmitter = require('events');\n\nclass MyEmitter extends EventEmitter {}\n\nconst myEmitter = new MyEmitter();\nmyEmitter.on('event', () => {\n console.log('an event occurred!');\n});\nmyEmitter.emit('event');
\n",
"modules": [
{
"textRaw": "Passing arguments and `this` to listeners",
"name": "passing_arguments_and_`this`_to_listeners",
"desc": "The eventEmitter.emit()
method allows an arbitrary set of arguments to be\npassed to the listener functions. It is important to keep in mind that when an\nordinary listener function is called by the EventEmitter
, the standard this
\nkeyword is intentionally set to reference the EventEmitter
to which the\nlistener is attached.\n\n
const myEmitter = new MyEmitter();\nmyEmitter.on('event', function(a, b) {\n console.log(a, b, this);\n // Prints:\n // a b MyEmitter {\n // domain: null,\n // _events: { event: [Function] },\n // _eventsCount: 1,\n // _maxListeners: undefined }\n});\nmyEmitter.emit('event', 'a', 'b');
\nIt is possible to use ES6 Arrow Functions as listeners, however, when doing so,\nthe this
keyword will no longer reference the EventEmitter
instance:\n\n
const myEmitter = new MyEmitter();\nmyEmitter.on('event', (a, b) => {\n console.log(a, b, this);\n // Prints: a b {}\n});\nmyEmitter.emit('event', 'a', 'b');
\n",
"type": "module",
"displayName": "Passing arguments and `this` to listeners"
},
{
"textRaw": "Asynchronous vs. Synchronous",
"name": "asynchronous_vs._synchronous",
"desc": "The EventListener
calls all listeners synchronously in the order in which\nthey were registered. This is important to ensure the proper sequencing of\nevents and to avoid race conditions or logic errors. When appropriate,\nlistener functions can switch to an asynchronous mode of operation using\nthe setImmediate()
or process.nextTick()
methods:\n\n
const myEmitter = new MyEmitter();\nmyEmitter.on('event', (a, b) => {\n setImmediate(() => {\n console.log('this happens asynchronously');\n });\n});\nmyEmitter.emit('event', 'a', 'b');
\n",
"type": "module",
"displayName": "Asynchronous vs. Synchronous"
},
{
"textRaw": "Handling events only once",
"name": "handling_events_only_once",
"desc": "When a listener is registered using the eventEmitter.on()
method, that\nlistener will be invoked every time the named event is emitted.\n\n
const myEmitter = new MyEmitter();\nvar m = 0;\nmyEmitter.on('event', () => {\n console.log(++m);\n});\nmyEmitter.emit('event');\n // Prints: 1\nmyEmitter.emit('event');\n // Prints: 2
\nUsing the eventEmitter.once()
method, it is possible to register a listener\nthat is unregistered before it is called.\n\n
const myEmitter = new MyEmitter();\nvar m = 0;\nmyEmitter.once('event', () => {\n console.log(++m);\n});\nmyEmitter.emit('event');\n // Prints: 1\nmyEmitter.emit('event');\n // Ignored
\n",
"type": "module",
"displayName": "Handling events only once"
},
{
"textRaw": "Error events",
"name": "error_events",
"desc": "When an error occurs within an EventEmitter
instance, the typical action is\nfor an 'error'
event to be emitted. These are treated as a special case\nwithin Node.js.\n\n
If an EventEmitter
does not have at least one listener registered for the\n'error'
event, and an 'error'
event is emitted, the error is thrown, a\nstack trace is printed, and the Node.js process exits.\n\n
const myEmitter = new MyEmitter();\nmyEmitter.emit('error', new Error('whoops!'));\n // Throws and crashes Node.js
\nTo guard against crashing the Node.js process, developers can either register\na listener for the process.on('uncaughtException')
event or use the\n[domain
][] module (Note, however, that the domain
module has been\ndeprecated).\n\n
const myEmitter = new MyEmitter();\n\nprocess.on('uncaughtException', (err) => {\n console.log('whoops! there was an error');\n});\n\nmyEmitter.emit('error', new Error('whoops!'));\n // Prints: whoops! there was an error
\nAs a best practice, developers should always register listeners for the\n'error'
event:\n\n
const myEmitter = new MyEmitter();\nmyEmitter.on('error', (err) => {\n console.log('whoops! there was an error');\n});\nmyEmitter.emit('error', new Error('whoops!'));\n // Prints: whoops! there was an error
\n",
"type": "module",
"displayName": "Error events"
}
],
"classes": [
{
"textRaw": "Class: EventEmitter",
"type": "class",
"name": "EventEmitter",
"desc": "The EventEmitter
class is defined and exposed by the events
module:\n\n
const EventEmitter = require('events');
\nAll EventEmitters emit the event 'newListener'
when new listeners are\nadded and 'removeListener'
when a listener is removed.\n\n
The EventEmitter
instance will emit it's own 'newListener'
event before\na listener is added to it's internal array of listeners.\n\n
Listeners registered for the 'newListener'
event will be passed the event\nname and a reference to the listener being added.\n\n
The fact that the event is triggered before adding the listener has a subtle\nbut important side effect: any additional listeners registered to the same\nname
within the 'newListener'
callback will be inserted before the\nlistener that is in the process of being added.\n\n
const myEmitter = new MyEmitter();\n// Only do this once so we don't loop forever\nmyEmitter.once('newListener', (event, listener) => {\n if (event === 'event') {\n // Insert a new listener in front\n myEmitter.on('event', () => {\n console.log('B');\n });\n }\n});\nmyEmitter.on('event', () => {\n console.log('A');\n});\nmyEmitter.emit('event');\n // Prints:\n // B\n // A
\n"
},
{
"textRaw": "Event: 'removeListener'",
"type": "event",
"name": "removeListener",
"params": [],
"desc": "The 'removeListener'
event is emitted after a listener is removed.\n\n
A class method that returns the number of listeners for the given eventName
\nregistered on the given emitter
.\n\n
const myEmitter = new MyEmitter();\nmyEmitter.on('event', () => {});\nmyEmitter.on('event', () => {});\nconsole.log(EventEmitter.listenerCount(myEmitter, 'event'));\n // Prints: 2
\n",
"signatures": [
{
"params": [
{
"name": "emitter"
},
{
"name": "eventName"
}
]
}
]
},
{
"textRaw": "emitter.addListener(eventName, listener)",
"type": "method",
"name": "addListener",
"desc": "Alias for emitter.on(eventName, listener)
.\n\n
Synchronously calls each of the listeners registered for the event named\neventName
, in the order they were registered, passing the supplied arguments\nto each.\n\n
Returns true
if the event had listeners, false
otherwise.\n\n
Returns an array listing the events for which the emitter has registered\nlisteners. The values in the array will be strings or Symbols.\n\n
\nconst EventEmitter = require('events');\nconst myEE = new EventEmitter();\nmyEE.on('foo', () => {});\nmyEE.on('bar', () => {});\n\nconst sym = Symbol('symbol');\nmyEE.on(sym, () => {});\n\nconsole.log(myEE.eventNames());\n // Prints [ 'foo', 'bar', Symbol(symbol) ]
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "emitter.getMaxListeners()",
"type": "method",
"name": "getMaxListeners",
"desc": "Returns the current max listener value for the EventEmitter
which is either\nset by [emitter.setMaxListeners(n)
][] or defaults to\n[EventEmitter.defaultMaxListeners
][].\n\n
Returns the number of listeners listening to the event named eventName
.\n\n
Returns a copy of the array of listeners for the event named eventName
.\n\n
server.on('connection', (stream) => {\n console.log('someone connected!');\n});\nconsole.log(util.inspect(server.listeners('connection')));\n // Prints: [ [Function] ]
\n",
"signatures": [
{
"params": [
{
"name": "eventName"
}
]
}
]
},
{
"textRaw": "emitter.on(eventName, listener)",
"type": "method",
"name": "on",
"signatures": [
{
"params": [
{
"textRaw": "`eventName` {string|Symbol} The name of the event. ",
"name": "eventName",
"type": "string|Symbol",
"desc": "The name of the event."
},
{
"textRaw": "`listener` {Function} The callback function ",
"name": "listener",
"type": "Function",
"desc": "The callback function"
}
]
},
{
"params": [
{
"name": "eventName"
},
{
"name": "listener"
}
]
}
],
"desc": "Adds the listener
function to the end of the listeners array for the\nevent named eventName
. No checks are made to see if the listener
has\nalready been added. Multiple calls passing the same combination of eventName
\nand listener
will result in the listener
being added, and called, multiple\ntimes.\n\n
server.on('connection', (stream) => {\n console.log('someone connected!');\n});
\nReturns a reference to the EventEmitter
so calls can be chained.\n\n
By default, event listeners are invoked in the order they are added. The\nemitter.prependListener()
method can be used as an alternative to add the\nevent listener to the beginning of the listeners array.\n\n
const myEE = new EventEmitter();\nmyEE.on('foo', () => console.log('a'));\nmyEE.prependListener('foo', () => console.log('b'));\nmyEE.emit('foo');\n // Prints:\n // b\n // a
\n"
},
{
"textRaw": "emitter.once(eventName, listener)",
"type": "method",
"name": "once",
"signatures": [
{
"params": [
{
"textRaw": "`eventName` {string|Symbol} The name of the event. ",
"name": "eventName",
"type": "string|Symbol",
"desc": "The name of the event."
},
{
"textRaw": "`listener` {Function} The callback function ",
"name": "listener",
"type": "Function",
"desc": "The callback function"
}
]
},
{
"params": [
{
"name": "eventName"
},
{
"name": "listener"
}
]
}
],
"desc": "Adds a one time listener
function for the event named eventName
. The\nnext time eventName
is triggered, this listener is removed and then invoked.\n\n
server.once('connection', (stream) => {\n console.log('Ah, we have our first user!');\n});
\nReturns a reference to the EventEmitter
so calls can be chained.\n\n
By default, event listeners are invoked in the order they are added. The\nemitter.prependOnceListener()
method can be used as an alternative to add the\nevent listener to the beginning of the listeners array.\n\n
const myEE = new EventEmitter();\nmyEE.once('foo', () => console.log('a'));\nmyEE.prependOnceListener('foo', () => console.log('b'));\nmyEE.emit('foo');\n // Prints:\n // b\n // a
\n"
},
{
"textRaw": "emitter.prependListener(eventName, listener)",
"type": "method",
"name": "prependListener",
"signatures": [
{
"params": [
{
"textRaw": "`eventName` {string|Symbol} The name of the event. ",
"name": "eventName",
"type": "string|Symbol",
"desc": "The name of the event."
},
{
"textRaw": "`listener` {Function} The callback function ",
"name": "listener",
"type": "Function",
"desc": "The callback function"
}
]
},
{
"params": [
{
"name": "eventName"
},
{
"name": "listener"
}
]
}
],
"desc": "Adds the listener
function to the beginning of the listeners array for the\nevent named eventName
. No checks are made to see if the listener
has\nalready been added. Multiple calls passing the same combination of eventName
\nand listener
will result in the listener
being added, and called, multiple\ntimes.\n\n
server.prependListener('connection', (stream) => {\n console.log('someone connected!');\n});
\nReturns a reference to the EventEmitter
so calls can be chained.\n\n
Adds a one time listener
function for the event named eventName
to the\nbeginning of the listeners array. The next time eventName
is triggered, this\nlistener is removed, and then invoked.\n\n
server.prependOnceListener('connection', (stream) => {\n console.log('Ah, we have our first user!');\n});
\nReturns a reference to the EventEmitter
so calls can be chained.\n\n
Removes all listeners, or those of the specified eventName
.\n\n
Note that it is bad practice to remove listeners added elsewhere in the code,\nparticularly when the EventEmitter
instance was created by some other\ncomponent or module (e.g. sockets or file streams).\n\n
Returns a reference to the EventEmitter
so calls can be chained.\n\n
Removes the specified listener
from the listener array for the event named\neventName
.\n\n
var callback = (stream) => {\n console.log('someone connected!');\n};\nserver.on('connection', callback);\n// ...\nserver.removeListener('connection', callback);
\nremoveListener
will remove, at most, one instance of a listener from the\nlistener array. If any single listener has been added multiple times to the\nlistener array for the specified eventName
, then removeListener
must be\ncalled multiple times to remove each instance.\n\n
Note that once an event has been emitted, all listeners attached to it at the\ntime of emitting will be called in order. This implies that any removeListener()
\nor removeAllListeners()
calls after emitting and before the last listener\nfinishes execution will not remove them from emit()
in progress. Subsequent\nevents will behave as expected.\n\n
const myEmitter = new MyEmitter();\n\nvar callbackA = () => {\n console.log('A');\n myEmitter.removeListener('event', callbackB);\n};\n\nvar callbackB = () => {\n console.log('B');\n};\n\nmyEmitter.on('event', callbackA);\n\nmyEmitter.on('event', callbackB);\n\n// callbackA removes listener callbackB but it will still be called.\n// Internal listener array at time of emit [callbackA, callbackB]\nmyEmitter.emit('event');\n // Prints:\n // A\n // B\n\n// callbackB is now removed.\n// Internal listener array [callbackA]\nmyEmitter.emit('event');\n // Prints:\n // A
\nBecause listeners are managed using an internal array, calling this will\nchange the position indices of any listener registered after the listener\nbeing removed. This will not impact the order in which listeners are called,\nbut it will means that any copies of the listener array as returned by\nthe emitter.listeners()
method will need to be recreated.\n\n
Returns a reference to the EventEmitter
so calls can be chained.\n\n
By default EventEmitters will print a warning if more than 10
listeners are\nadded for a particular event. This is a useful default that helps finding\nmemory leaks. Obviously, not all events should be limited to just 10 listeners.\nThe emitter.setMaxListeners()
method allows the limit to be modified for this\nspecific EventEmitter
instance. The value can be set to Infinity
(or 0
)\nfor to indicate an unlimited number of listeners.\n\n
Returns a reference to the EventEmitter
so calls can be chained.\n\n
By default, a maximum of 10
listeners can be registered for any single\nevent. This limit can be changed for individual EventEmitter
instances\nusing the [emitter.setMaxListeners(n)
][] method. To change the default\nfor all EventEmitter
instances, the EventEmitter.defaultMaxListeners
\nproperty can be used.\n\n
Take caution when setting the EventEmitter.defaultMaxListeners
because the\nchange effects all EventEmitter
instances, including those created before\nthe change is made. However, calling [emitter.setMaxListeners(n)
][] still has\nprecedence over EventEmitter.defaultMaxListeners
.\n\n
Note that this is not a hard limit. The EventEmitter
instance will allow\nmore listeners to be added but will output a trace warning to stderr indicating\nthat a possible EventEmitter memory leak
has been detected. For any single\nEventEmitter
, the emitter.getMaxListeners()
and emitter.setMaxListeners()
\nmethods can be used to temporarily avoid this warning:\n\n
emitter.setMaxListeners(emitter.getMaxListeners() + 1);\nemitter.once('event', () => {\n // do stuff\n emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));\n});
\n"
}
]
}
]
},
{
"textRaw": "File System",
"name": "fs",
"stability": 2,
"stabilityText": "Stable",
"desc": "File I/O is provided by simple wrappers around standard POSIX functions. To\nuse this module do require('fs')
. All the methods have asynchronous and\nsynchronous forms.\n\n
The asynchronous form always takes a completion callback as its last argument.\nThe arguments passed to the completion callback depend on the method, but the\nfirst argument is always reserved for an exception. If the operation was\ncompleted successfully, then the first argument will be null
or undefined
.\n\n
When using the synchronous form any exceptions are immediately thrown.\nYou can use try/catch to handle exceptions or allow them to bubble up.\n\n
\nHere is an example of the asynchronous version:\n\n
\nconst fs = require('fs');\n\nfs.unlink('/tmp/hello', (err) => {\n if (err) throw err;\n console.log('successfully deleted /tmp/hello');\n});
\nHere is the synchronous version:\n\n
\nconst fs = require('fs');\n\nfs.unlinkSync('/tmp/hello');\nconsole.log('successfully deleted /tmp/hello');
\nWith the asynchronous methods there is no guaranteed ordering. So the\nfollowing is prone to error:\n\n
\nfs.rename('/tmp/hello', '/tmp/world', (err) => {\n if (err) throw err;\n console.log('renamed complete');\n});\nfs.stat('/tmp/world', (err, stats) => {\n if (err) throw err;\n console.log(`stats: ${JSON.stringify(stats)}`);\n});
\nIt could be that fs.stat
is executed before fs.rename
.\nThe correct way to do this is to chain the callbacks.\n\n
fs.rename('/tmp/hello', '/tmp/world', (err) => {\n if (err) throw err;\n fs.stat('/tmp/world', (err, stats) => {\n if (err) throw err;\n console.log(`stats: ${JSON.stringify(stats)}`);\n });\n});
\nIn busy processes, the programmer is strongly encouraged to use the\nasynchronous versions of these calls. The synchronous versions will block\nthe entire process until they complete--halting all connections.\n\n
\nThe relative path to a filename can be used. Remember, however, that this path\nwill be relative to process.cwd()
.\n\n
Most fs functions let you omit the callback argument. If you do, a default\ncallback is used that rethrows errors. To get a trace to the original call\nsite, set the NODE_DEBUG
environment variable:\n\n
$ cat script.js\nfunction bad() {\n require('fs').readFile('/');\n}\nbad();\n\n$ env NODE_DEBUG=fs node script.js\nfs.js:66\n throw err;\n ^\nError: EISDIR, read\n at rethrow (fs.js:61:21)\n at maybeCallback (fs.js:79:42)\n at Object.fs.readFile (fs.js:153:18)\n at bad (/path/to/script.js:2:17)\n at Object.<anonymous> (/path/to/script.js:5:1)\n <etc.>
\n",
"modules": [
{
"textRaw": "Buffer API",
"name": "buffer_api",
"desc": "fs
functions support passing and receiving paths as both strings\nand Buffers. The latter is intended to make it possible to work with\nfilesystems that allow for non-UTF-8 filenames. For most typical\nuses, working with paths as Buffers will be unnecessary, as the string\nAPI converts to and from UTF-8 automatically.\n\n
Note that on certain file systems (such as NTFS and HFS+) filenames\nwill always be encoded as UTF-8. On such file systems, passing\nnon-UTF-8 encoded Buffers to fs
functions will not work as expected.\n\n
Objects returned from fs.watch()
are of this type.\n\n
Emitted when something changes in a watched directory or file.\nSee more details in [fs.watch()
][].\n\n
The filename
argument may not be provided depending on operating system\nsupport. If filename
is provided, it will be provided as a Buffer
if\nfs.watch()
is called with it's encoding
option set to 'buffer'
, otherwise\nfilename
will be a string.\n\n
fs.watch('./tmp', {encoding: 'buffer'}, (event, filename) => {\n if (filename)\n console.log(filename);\n // Prints: <Buffer ...>\n});
\n"
},
{
"textRaw": "Event: 'error'",
"type": "event",
"name": "error",
"params": [],
"desc": "Emitted when an error occurs.\n\n
\n" } ], "methods": [ { "textRaw": "watcher.close()", "type": "method", "name": "close", "desc": "Stop watching for changes on the given fs.FSWatcher
.\n\n
ReadStream
is a [Readable Stream][].\n\n
Emitted when the ReadStream's file is opened.\n\n
\n" }, { "textRaw": "Event: 'close'", "type": "event", "name": "close", "desc": "Emitted when the ReadStream
's underlying file descriptor has been closed\nusing the fs.close()
method.\n\n
The path to the file the stream is reading from as specified in the first\nargument to fs.createReadStream()
. If path
is passed as a string, then\nreadStream.path
will be a string. If path
is passed as a Buffer
, then\nreadStream.path
will be a Buffer
.\n\n
Objects returned from [fs.stat()
][], [fs.lstat()
][] and [fs.fstat()
][] and their\nsynchronous counterparts are of this type.\n\n
stats.isFile()
stats.isDirectory()
stats.isBlockDevice()
stats.isCharacterDevice()
stats.isSymbolicLink()
(only valid with [fs.lstat()
][])stats.isFIFO()
stats.isSocket()
For a regular file [util.inspect(stats)
][] would return a string very\nsimilar to this:\n\n
{\n dev: 2114,\n ino: 48064969,\n mode: 33188,\n nlink: 1,\n uid: 85,\n gid: 100,\n rdev: 0,\n size: 527,\n blksize: 4096,\n blocks: 8,\n atime: Mon, 10 Oct 2011 23:24:11 GMT,\n mtime: Mon, 10 Oct 2011 23:24:11 GMT,\n ctime: Mon, 10 Oct 2011 23:24:11 GMT,\n birthtime: Mon, 10 Oct 2011 23:24:11 GMT\n}
\nPlease note that atime
, mtime
, birthtime
, and ctime
are\ninstances of [Date
][MDN-Date] object and to compare the values of\nthese objects you should use appropriate methods. For most general\nuses [getTime()
][MDN-Date-getTime] will return the number of\nmilliseconds elapsed since 1 January 1970 00:00:00 UTC and this\ninteger should be sufficient for any comparison, however there are\nadditional methods which can be used for displaying fuzzy information.\nMore details can be found in the [MDN JavaScript Reference][MDN-Date]\npage.\n\n
The times in the stat object have the following semantics:\n\n
\natime
"Access Time" - Time when file data last accessed. Changed\nby the mknod(2)
, utimes(2)
, and read(2)
system calls.mtime
"Modified Time" - Time when file data last modified.\nChanged by the mknod(2)
, utimes(2)
, and write(2)
system calls.ctime
"Change Time" - Time when file status was last changed\n(inode data modification). Changed by the chmod(2)
, chown(2)
,\nlink(2)
, mknod(2)
, rename(2)
, unlink(2)
, utimes(2)
,\nread(2)
, and write(2)
system calls.birthtime
"Birth Time" - Time of file creation. Set once when the\nfile is created. On filesystems where birthtime is not available,\nthis field may instead hold either the ctime
or\n1970-01-01T00:00Z
(ie, unix epoch timestamp 0
). Note that this\nvalue may be greater than atime
or mtime
in this case. On Darwin\nand other FreeBSD variants, also set if the atime
is explicitly\nset to an earlier value than the current birthtime
using the\nutimes(2)
system call.Prior to Node v0.12, the ctime
held the birthtime
on Windows\nsystems. Note that as of v0.12, ctime
is not "creation time", and\non Unix systems, it never was.\n\n
WriteStream
is a [Writable Stream][].\n\n
Emitted when the WriteStream's file is opened.\n\n
\n" }, { "textRaw": "Event: 'close'", "type": "event", "name": "close", "desc": "Emitted when the WriteStream
's underlying file descriptor has been closed\nusing the fs.close()
method.\n\n
The number of bytes written so far. Does not include data that is still queued\nfor writing.\n\n
\n" }, { "textRaw": "writeStream.path", "name": "path", "desc": "The path to the file the stream is writing to as specified in the first\nargument to fs.createWriteStream()
. If path
is passed as a string, then\nwriteStream.path
will be a string. If path
is passed as a Buffer
, then\nwriteStream.path
will be a Buffer
.\n\n
Tests a user's permissions for the file specified by path
. mode
is an\noptional integer that specifies the accessibility checks to be performed. The\nfollowing constants define the possible values of mode
. It is possible to\ncreate a mask consisting of the bitwise OR of two or more values.\n\n
fs.F_OK
- File is visible to the calling process. This is useful for\ndetermining if a file exists, but says nothing about rwx
permissions.\nDefault if no mode
is specified.fs.R_OK
- File can be read by the calling process.fs.W_OK
- File can be written by the calling process.fs.X_OK
- File can be executed by the calling process. This has no effect\non Windows (will behave like fs.F_OK
).The final argument, callback
, is a callback function that is invoked with\na possible error argument. If any of the accessibility checks fail, the error\nargument will be populated. The following example checks if the file\n/etc/passwd
can be read and written by the current process.\n\n
fs.access('/etc/passwd', fs.R_OK | fs.W_OK, (err) => {\n console.log(err ? 'no access!' : 'can read/write');\n});
\n"
},
{
"textRaw": "fs.accessSync(path[, mode])",
"type": "method",
"name": "accessSync",
"signatures": [
{
"params": [
{
"textRaw": "`path` {String | Buffer} ",
"name": "path",
"type": "String | Buffer"
},
{
"textRaw": "`mode` {Integer} ",
"name": "mode",
"type": "Integer",
"optional": true
}
]
},
{
"params": [
{
"name": "path"
},
{
"name": "mode",
"optional": true
}
]
}
],
"desc": "Synchronous version of [fs.access()
][]. This throws if any accessibility checks\nfail, and does nothing otherwise.\n\n
Asynchronously append data to a file, creating the file if it does not yet exist.\ndata
can be a string or a buffer.\n\n
Example:\n\n
\nfs.appendFile('message.txt', 'data to append', (err) => {\n if (err) throw err;\n console.log('The "data to append" was appended to file!');\n});
\nIf options
is a string, then it specifies the encoding. Example:\n\n
fs.appendFile('message.txt', 'data to append', 'utf8', callback);
\nAny specified file descriptor has to have been opened for appending.\n\n
\nNote: Specified file descriptors will not be closed automatically.\n\n
\n" }, { "textRaw": "fs.appendFileSync(file, data[, options])", "type": "method", "name": "appendFileSync", "signatures": [ { "params": [ { "textRaw": "`file` {String | Buffer} ", "name": "file", "type": "String | Buffer" }, { "textRaw": "`data` {String | Buffer} ", "name": "data", "type": "String | Buffer" }, { "textRaw": "`options` {Object | String} ", "options": [ { "textRaw": "`encoding` {String | Null} default = `'utf8'` ", "name": "encoding", "type": "String | Null", "desc": "default = `'utf8'`" }, { "textRaw": "`mode` {Integer} default = `0o666` ", "name": "mode", "type": "Integer", "desc": "default = `0o666`" }, { "textRaw": "`flag` {String} default = `'a'` ", "name": "flag", "type": "String", "desc": "default = `'a'`" } ], "name": "options", "type": "Object | String", "optional": true } ] }, { "params": [ { "name": "file" }, { "name": "data" }, { "name": "options", "optional": true } ] } ], "desc": "The synchronous version of [fs.appendFile()
][]. Returns undefined
.\n\n
Asynchronous chmod(2). No arguments other than a possible exception are given\nto the completion callback.\n\n
\n" }, { "textRaw": "fs.chmodSync(path, mode)", "type": "method", "name": "chmodSync", "signatures": [ { "params": [ { "textRaw": "`path` {String | Buffer} ", "name": "path", "type": "String | Buffer" }, { "textRaw": "`mode` {Integer} ", "name": "mode", "type": "Integer" } ] }, { "params": [ { "name": "path" }, { "name": "mode" } ] } ], "desc": "Synchronous chmod(2). Returns undefined
.\n\n
Asynchronous chown(2). No arguments other than a possible exception are given\nto the completion callback.\n\n
\n" }, { "textRaw": "fs.chownSync(path, uid, gid)", "type": "method", "name": "chownSync", "signatures": [ { "params": [ { "textRaw": "`path` {String | Buffer} ", "name": "path", "type": "String | Buffer" }, { "textRaw": "`uid` {Integer} ", "name": "uid", "type": "Integer" }, { "textRaw": "`gid` {Integer} ", "name": "gid", "type": "Integer" } ] }, { "params": [ { "name": "path" }, { "name": "uid" }, { "name": "gid" } ] } ], "desc": "Synchronous chown(2). Returns undefined
.\n\n
Asynchronous close(2). No arguments other than a possible exception are given\nto the completion callback.\n\n
\n" }, { "textRaw": "fs.closeSync(fd)", "type": "method", "name": "closeSync", "signatures": [ { "params": [ { "textRaw": "`fd` {Integer} ", "name": "fd", "type": "Integer" } ] }, { "params": [ { "name": "fd" } ] } ], "desc": "Synchronous close(2). Returns undefined
.\n\n
Returns a new [ReadStream
][] object. (See [Readable Stream][]).\n\n
Be aware that, unlike the default value set for highWaterMark
on a\nreadable stream (16 kb), the stream returned by this method has a\ndefault value of 64 kb for the same parameter.\n\n
options
is an object or string with the following defaults:\n\n
{\n flags: 'r',\n encoding: null,\n fd: null,\n mode: 0o666,\n autoClose: true\n}
\noptions
can include start
and end
values to read a range of bytes from\nthe file instead of the entire file. Both start
and end
are inclusive and\nstart at 0. The encoding
can be any one of those accepted by [Buffer
][].\n\n
If fd
is specified, ReadStream
will ignore the path
argument and will use\nthe specified file descriptor. This means that no 'open'
event will be emitted.\nNote that fd
should be blocking; non-blocking fd
s should be passed to\n[net.Socket
][].\n\n
If autoClose
is false, then the file descriptor won't be closed, even if\nthere's an error. It is your responsibility to close it and make sure\nthere's no file descriptor leak. If autoClose
is set to true (default\nbehavior), on error
or end
the file descriptor will be closed\nautomatically.\n\n
mode
sets the file mode (permission and sticky bits), but only if the\nfile was created.\n\n
An example to read the last 10 bytes of a file which is 100 bytes long:\n\n
\nfs.createReadStream('sample.txt', {start: 90, end: 99});
\nIf options
is a string, then it specifies the encoding.\n\n
Returns a new [WriteStream
][] object. (See [Writable Stream][]).\n\n
options
is an object or string with the following defaults:\n\n
{\n flags: 'w',\n defaultEncoding: 'utf8',\n fd: null,\n mode: 0o666,\n autoClose: true\n}
\noptions
may also include a start
option to allow writing data at\nsome position past the beginning of the file. Modifying a file rather\nthan replacing it may require a flags
mode of r+
rather than the\ndefault mode w
. The defaultEncoding
can be any one of those accepted by [Buffer
][].\n\n
If autoClose
is set to true (default behavior) on error
or end
\nthe file descriptor will be closed automatically. If autoClose
is false,\nthen the file descriptor won't be closed, even if there's an error.\nIt is your responsibility to close it and make sure\nthere's no file descriptor leak.\n\n
Like [ReadStream
][], if fd
is specified, WriteStream
will ignore the\npath
argument and will use the specified file descriptor. This means that no\n'open'
event will be emitted. Note that fd
should be blocking; non-blocking\nfd
s should be passed to [net.Socket
][].\n\n
If options
is a string, then it specifies the encoding.\n\n
Test whether or not the given path exists by checking with the file system.\nThen call the callback
argument with either true or false. Example:\n\n
fs.exists('/etc/passwd', (exists) => {\n console.log(exists ? 'it\\'s there' : 'no passwd!');\n});
\nfs.exists()
should not be used to check if a file exists before calling\nfs.open()
. Doing so introduces a race condition since other processes may\nchange the file's state between the two calls. Instead, user code should\ncall fs.open()
directly and handle the error raised if the file is\nnon-existent.\n\n
Synchronous version of [fs.exists()
][].\nReturns true
if the file exists, false
otherwise.\n\n
Asynchronous fchmod(2). No arguments other than a possible exception\nare given to the completion callback.\n\n
\n" }, { "textRaw": "fs.fchmodSync(fd, mode)", "type": "method", "name": "fchmodSync", "signatures": [ { "params": [ { "textRaw": "`fd` {Integer} ", "name": "fd", "type": "Integer" }, { "textRaw": "`mode` {Integer} ", "name": "mode", "type": "Integer" } ] }, { "params": [ { "name": "fd" }, { "name": "mode" } ] } ], "desc": "Synchronous fchmod(2). Returns undefined
.\n\n
Asynchronous fchown(2). No arguments other than a possible exception are given\nto the completion callback.\n\n
\n" }, { "textRaw": "fs.fchownSync(fd, uid, gid)", "type": "method", "name": "fchownSync", "signatures": [ { "params": [ { "textRaw": "`fd` {Integer} ", "name": "fd", "type": "Integer" }, { "textRaw": "`uid` {Integer} ", "name": "uid", "type": "Integer" }, { "textRaw": "`gid` {Integer} ", "name": "gid", "type": "Integer" } ] }, { "params": [ { "name": "fd" }, { "name": "uid" }, { "name": "gid" } ] } ], "desc": "Synchronous fchown(2). Returns undefined
.\n\n
Asynchronous fdatasync(2). No arguments other than a possible exception are\ngiven to the completion callback.\n\n
\n" }, { "textRaw": "fs.fdatasyncSync(fd)", "type": "method", "name": "fdatasyncSync", "signatures": [ { "params": [ { "textRaw": "`fd` {Integer} ", "name": "fd", "type": "Integer" } ] }, { "params": [ { "name": "fd" } ] } ], "desc": "Synchronous fdatasync(2). Returns undefined
.\n\n
Asynchronous fstat(2). The callback gets two arguments (err, stats)
where\nstats
is a [fs.Stats
][] object. fstat()
is identical to [stat()
][],\nexcept that the file to be stat-ed is specified by the file descriptor fd
.\n\n
Synchronous fstat(2). Returns an instance of fs.Stats
.\n\n
Asynchronous fsync(2). No arguments other than a possible exception are given\nto the completion callback.\n\n
\n" }, { "textRaw": "fs.fsyncSync(fd)", "type": "method", "name": "fsyncSync", "signatures": [ { "params": [ { "textRaw": "`fd` {Integer} ", "name": "fd", "type": "Integer" } ] }, { "params": [ { "name": "fd" } ] } ], "desc": "Synchronous fsync(2). Returns undefined
.\n\n
Asynchronous ftruncate(2). No arguments other than a possible exception are\ngiven to the completion callback.\n\n
\n" }, { "textRaw": "fs.ftruncateSync(fd, len)", "type": "method", "name": "ftruncateSync", "signatures": [ { "params": [ { "textRaw": "`fd` {Integer} ", "name": "fd", "type": "Integer" }, { "textRaw": "`len` {Integer} ", "name": "len", "type": "Integer" } ] }, { "params": [ { "name": "fd" }, { "name": "len" } ] } ], "desc": "Synchronous ftruncate(2). Returns undefined
.\n\n
Change the file timestamps of a file referenced by the supplied file\ndescriptor.\n\n
\n" }, { "textRaw": "fs.futimesSync(fd, atime, mtime)", "type": "method", "name": "futimesSync", "signatures": [ { "params": [ { "textRaw": "`fd` {Integer} ", "name": "fd", "type": "Integer" }, { "textRaw": "`atime` {Integer} ", "name": "atime", "type": "Integer" }, { "textRaw": "`mtime` {Integer} ", "name": "mtime", "type": "Integer" } ] }, { "params": [ { "name": "fd" }, { "name": "atime" }, { "name": "mtime" } ] } ], "desc": "Synchronous version of [fs.futimes()
][]. Returns undefined
.\n\n
Asynchronous lchmod(2). No arguments other than a possible exception\nare given to the completion callback.\n\n
\nOnly available on Mac OS X.\n\n
\n" }, { "textRaw": "fs.lchmodSync(path, mode)", "type": "method", "name": "lchmodSync", "signatures": [ { "params": [ { "textRaw": "`path` {String | Buffer} ", "name": "path", "type": "String | Buffer" }, { "textRaw": "`mode` {Integer} ", "name": "mode", "type": "Integer" } ] }, { "params": [ { "name": "path" }, { "name": "mode" } ] } ], "desc": "Synchronous lchmod(2). Returns undefined
.\n\n
Asynchronous lchown(2). No arguments other than a possible exception are given\nto the completion callback.\n\n
\n" }, { "textRaw": "fs.lchownSync(path, uid, gid)", "type": "method", "name": "lchownSync", "signatures": [ { "params": [ { "textRaw": "`path` {String | Buffer} ", "name": "path", "type": "String | Buffer" }, { "textRaw": "`uid` {Integer} ", "name": "uid", "type": "Integer" }, { "textRaw": "`gid` {Integer} ", "name": "gid", "type": "Integer" } ] }, { "params": [ { "name": "path" }, { "name": "uid" }, { "name": "gid" } ] } ], "desc": "Synchronous lchown(2). Returns undefined
.\n\n
Asynchronous link(2). No arguments other than a possible exception are given to\nthe completion callback.\n\n
\n" }, { "textRaw": "fs.linkSync(srcpath, dstpath)", "type": "method", "name": "linkSync", "signatures": [ { "params": [ { "textRaw": "`srcpath` {String | Buffer} ", "name": "srcpath", "type": "String | Buffer" }, { "textRaw": "`dstpath` {String | Buffer} ", "name": "dstpath", "type": "String | Buffer" } ] }, { "params": [ { "name": "srcpath" }, { "name": "dstpath" } ] } ], "desc": "Synchronous link(2). Returns undefined
.\n\n
Asynchronous lstat(2). The callback gets two arguments (err, stats)
where\nstats
is a [fs.Stats
][] object. lstat()
is identical to stat()
,\nexcept that if path
is a symbolic link, then the link itself is stat-ed,\nnot the file that it refers to.\n\n
Synchronous lstat(2). Returns an instance of fs.Stats
.\n\n
Asynchronous mkdir(2). No arguments other than a possible exception are given\nto the completion callback. mode
defaults to 0o777
.\n\n
Synchronous mkdir(2). Returns undefined
.\n\n
Creates a unique temporary directory.\n\n
\nGenerates six random characters to be appended behind a required\nprefix
to create a unique temporary directory.\n\n
The created folder path is passed as a string to the callback's second\nparameter.\n\n
\nExample:\n\n
\nfs.mkdtemp('/tmp/foo-', (err, folder) => {\n console.log(folder);\n // Prints: /tmp/foo-itXde2\n});
\n",
"signatures": [
{
"params": [
{
"name": "prefix"
},
{
"name": "callback"
}
]
}
]
},
{
"textRaw": "fs.mkdtempSync(template)",
"type": "method",
"name": "mkdtempSync",
"desc": "The synchronous version of [fs.mkdtemp()
][]. Returns the created\nfolder path.\n\n
Asynchronous file open. See open(2). flags
can be:\n\n
'r'
- Open file for reading.\nAn exception occurs if the file does not exist.
'r+'
- Open file for reading and writing.\nAn exception occurs if the file does not exist.
'rs'
- Open file for reading in synchronous mode. Instructs the operating\nsystem to bypass the local file system cache.
This is primarily useful for opening files on NFS mounts as it allows you to\nskip the potentially stale local cache. It has a very real impact on I/O\nperformance so don't use this flag unless you need it.
\nNote that this doesn't turn fs.open()
into a synchronous blocking call.\nIf that's what you want then you should be using fs.openSync()
'rs+'
- Open file for reading and writing, telling the OS to open it\nsynchronously. See notes for 'rs'
about using this with caution.
'w'
- Open file for writing.\nThe file is created (if it does not exist) or truncated (if it exists).
'wx'
- Like 'w'
but fails if path
exists.
'w+'
- Open file for reading and writing.\nThe file is created (if it does not exist) or truncated (if it exists).
'wx+'
- Like 'w+'
but fails if path
exists.
'a'
- Open file for appending.\nThe file is created if it does not exist.
'ax'
- Like 'a'
but fails if path
exists.
'a+'
- Open file for reading and appending.\nThe file is created if it does not exist.
'ax+'
- Like 'a+'
but fails if path
exists.
mode
sets the file mode (permission and sticky bits), but only if the file was\ncreated. It defaults to 0666
, readable and writable.\n\n
The callback gets two arguments (err, fd)
.\n\n
The exclusive flag 'x'
(O_EXCL
flag in open(2)) ensures that path
is newly\ncreated. On POSIX systems, path
is considered to exist even if it is a symlink\nto a non-existent file. The exclusive flag may or may not work with network file\nsystems.\n\n
flags
can also be a number as documented by open(2); commonly used constants\nare available from require('constants')
. On Windows, flags are translated to\ntheir equivalent ones where applicable, e.g. O_WRONLY
to FILE_GENERIC_WRITE
,\nor O_EXCL|O_CREAT
to CREATE_NEW
, as accepted by CreateFileW.\n\n
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.\n\n
\nNote: The behavior of fs.open()
is platform specific for some flags. As such,\nopening a directory on OS X and Linux with the 'a+'
flag - see example below -\nwill return an error. In contrast, on Windows and FreeBSD, a file descriptor\nwill be returned.\n\n
// OS X and Linux\nfs.open('<directory>', 'a+', (err, fd) => {\n // => [Error: EISDIR: illegal operation on a directory, open <directory>]\n})\n\n// Windows and FreeBSD\nfs.open('<directory>', 'a+', (err, fd) => {\n // => null, <fd>\n})
\n"
},
{
"textRaw": "fs.openSync(path, flags[, mode])",
"type": "method",
"name": "openSync",
"signatures": [
{
"params": [
{
"textRaw": "`path` {String | Buffer} ",
"name": "path",
"type": "String | Buffer"
},
{
"textRaw": "`flags` {String | Number} ",
"name": "flags",
"type": "String | Number"
},
{
"textRaw": "`mode` {Integer} ",
"name": "mode",
"type": "Integer",
"optional": true
}
]
},
{
"params": [
{
"name": "path"
},
{
"name": "flags"
},
{
"name": "mode",
"optional": true
}
]
}
],
"desc": "Synchronous version of [fs.open()
][]. Returns an integer representing the file\ndescriptor.\n\n
Read data from the file specified by fd
.\n\n
buffer
is the buffer that the data will be written to.\n\n
offset
is the offset in the buffer to start writing at.\n\n
length
is an integer specifying the number of bytes to read.\n\n
position
is an integer specifying where to begin reading from in the file.\nIf position
is null
, data will be read from the current file position.\n\n
The callback is given the three arguments, (err, bytesRead, buffer)
.\n\n
Asynchronous readdir(3). Reads the contents of a directory.\nThe callback gets two arguments (err, files)
where files
is an array of\nthe names of the files in the directory excluding '.'
and '..'
.\n\n
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe filenames passed to the callback. If the encoding
is set to 'buffer'
,\nthe filenames returned will be passed as Buffer
objects.\n\n
Synchronous readdir(3). Returns an array of filenames excluding '.'
and\n'..'
.\n\n
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe filenames passed to the callback. If the encoding
is set to 'buffer'
,\nthe filenames returned will be passed as Buffer
objects.\n\n
Asynchronously reads the entire contents of a file. Example:\n\n
\nfs.readFile('/etc/passwd', (err, data) => {\n if (err) throw err;\n console.log(data);\n});
\nThe callback is passed two arguments (err, data)
, where data
is the\ncontents of the file.\n\n
If no encoding is specified, then the raw buffer is returned.\n\n
\nIf options
is a string, then it specifies the encoding. Example:\n\n
fs.readFile('/etc/passwd', 'utf8', callback);
\nAny specified file descriptor has to support reading.\n\n
\nNote: Specified file descriptors will not be closed automatically.\n\n
\n" }, { "textRaw": "fs.readFileSync(file[, options])", "type": "method", "name": "readFileSync", "signatures": [ { "params": [ { "textRaw": "`file` {String | Buffer | Integer} filename or file descriptor ", "name": "file", "type": "String | Buffer | Integer", "desc": "filename or file descriptor" }, { "textRaw": "`options` {Object | String} ", "options": [ { "textRaw": "`encoding` {String | Null} default = `null` ", "name": "encoding", "type": "String | Null", "desc": "default = `null`" }, { "textRaw": "`flag` {String} default = `'r'` ", "name": "flag", "type": "String", "desc": "default = `'r'`" } ], "name": "options", "type": "Object | String", "optional": true } ] }, { "params": [ { "name": "file" }, { "name": "options", "optional": true } ] } ], "desc": "Synchronous version of [fs.readFile
][]. Returns the contents of the file
.\n\n
If the encoding
option is specified then this function returns a\nstring. Otherwise it returns a buffer.\n\n
Asynchronous readlink(2). The callback gets two arguments (err,\nlinkString)
.\n\n
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe link path passed to the callback. If the encoding
is set to 'buffer'
,\nthe link path returned will be passed as a Buffer
object.\n\n
Synchronous readlink(2). Returns the symbolic link's string value.\n\n
\nThe optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe link path passed to the callback. If the encoding
is set to 'buffer'
,\nthe link path returned will be passed as a Buffer
object.\n\n
Synchronous version of [fs.read()
][]. Returns the number of bytesRead
.\n\n
Asynchronous realpath(3). The callback
gets two arguments (err,\nresolvedPath)
. May use process.cwd
to resolve relative paths.\n\n
The optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe path passed to the callback. If the encoding
is set to 'buffer'
,\nthe path returned will be passed as a Buffer
object.\n\n
Synchronous realpath(3). Returns the resolved path.\n\n
\nThe optional options
argument can be a string specifying an encoding, or an\nobject with an encoding
property specifying the character encoding to use for\nthe path passed to the callback. If the encoding
is set to 'buffer'
,\nthe path returned will be passed as a Buffer
object.\n\n
Asynchronous rename(2). No arguments other than a possible exception are given\nto the completion callback.\n\n
\n" }, { "textRaw": "fs.renameSync(oldPath, newPath)", "type": "method", "name": "renameSync", "signatures": [ { "params": [ { "textRaw": "`oldPath` {String | Buffer} ", "name": "oldPath", "type": "String | Buffer" }, { "textRaw": "`newPath` {String | Buffer} ", "name": "newPath", "type": "String | Buffer" } ] }, { "params": [ { "name": "oldPath" }, { "name": "newPath" } ] } ], "desc": "Synchronous rename(2). Returns undefined
.\n\n
Asynchronous rmdir(2). No arguments other than a possible exception are given\nto the completion callback.\n\n
\n" }, { "textRaw": "fs.rmdirSync(path)", "type": "method", "name": "rmdirSync", "signatures": [ { "params": [ { "textRaw": "`path` {String | Buffer} ", "name": "path", "type": "String | Buffer" } ] }, { "params": [ { "name": "path" } ] } ], "desc": "Synchronous rmdir(2). Returns undefined
.\n\n
Asynchronous stat(2). The callback gets two arguments (err, stats)
where\nstats
is a [fs.Stats
][] object. See the [fs.Stats
][] section for more\ninformation.\n\n
Synchronous stat(2). Returns an instance of [fs.Stats
][].\n\n
Asynchronous symlink(2). No arguments other than a possible exception are given\nto the completion callback.\nThe type
argument can be set to 'dir'
, 'file'
, or 'junction'
(default\nis 'file'
) and is only available on Windows (ignored on other platforms).\nNote that Windows junction points require the destination path to be absolute. When using\n'junction'
, the target
argument will automatically be normalized to absolute path.\n\n
Here is an example below:\n\n
\nfs.symlink('./foo', './new-port');
\nIt creates a symbolic link named "new-port" that points to "foo".\n\n
\n" }, { "textRaw": "fs.symlinkSync(target, path[, type])", "type": "method", "name": "symlinkSync", "signatures": [ { "params": [ { "textRaw": "`target` {String | Buffer} ", "name": "target", "type": "String | Buffer" }, { "textRaw": "`path` {String | Buffer} ", "name": "path", "type": "String | Buffer" }, { "textRaw": "`type` {String} ", "name": "type", "type": "String", "optional": true } ] }, { "params": [ { "name": "target" }, { "name": "path" }, { "name": "type", "optional": true } ] } ], "desc": "Synchronous symlink(2). Returns undefined
.\n\n
Asynchronous truncate(2). No arguments other than a possible exception are\ngiven to the completion callback. A file descriptor can also be passed as the\nfirst argument. In this case, fs.ftruncate()
is called.\n\n
Synchronous truncate(2). Returns undefined
.\n\n
Asynchronous unlink(2). No arguments other than a possible exception are given\nto the completion callback.\n\n
\n" }, { "textRaw": "fs.unlinkSync(path)", "type": "method", "name": "unlinkSync", "signatures": [ { "params": [ { "textRaw": "`path` {String | Buffer} ", "name": "path", "type": "String | Buffer" } ] }, { "params": [ { "name": "path" } ] } ], "desc": "Synchronous unlink(2). Returns undefined
.\n\n
Stop watching for changes on filename
. If listener
is specified, only that\nparticular listener is removed. Otherwise, all listeners are removed and you\nhave effectively stopped watching filename
.\n\n
Calling fs.unwatchFile()
with a filename that is not being watched is a\nno-op, not an error.\n\n
Note: [fs.watch()
][] is more efficient than fs.watchFile()
and fs.unwatchFile()
.\nfs.watch()
should be used instead of fs.watchFile()
and fs.unwatchFile()
\nwhen possible.\n\n
Change file timestamps of the file referenced by the supplied path.\n\n
\nNote: the arguments atime
and mtime
of the following related functions does\nfollow the below rules:\n\n
'123456789'
, the value would get\nconverted to corresponding number.NaN
or Infinity
, the value would get converted to\nDate.now()
.Synchronous version of [fs.utimes()
][]. Returns undefined
.\n\n
Watch for changes on filename
, where filename
is either a file or a\ndirectory. The returned object is a [fs.FSWatcher
][].\n\n
The second argument is optional. If options
is provided as a string, it\nspecifies the encoding
. Otherwise options
should be passed as an object.\n\n
The listener callback gets two arguments (event, filename)
. event
is either\n'rename'
or 'change'
, and filename
is the name of the file which triggered\nthe event.\n\n
The fs.watch
API is not 100% consistent across platforms, and is\nunavailable in some situations.\n\n
The recursive option is only supported on OS X and Windows.\n\n
\n", "miscs": [ { "textRaw": "Availability", "name": "Availability", "type": "misc", "desc": "This feature depends on the underlying operating system providing a way\nto be notified of filesystem changes.\n\n
\ninotify
.kqueue
.kqueue
for files and 'FSEvents' for directories.event ports
.ReadDirectoryChangesW
.If the underlying functionality is not available for some reason, then\nfs.watch
will not be able to function. For example, watching files or\ndirectories on network file systems (NFS, SMB, etc.) often doesn't work\nreliably or at all.\n\n
You can still use fs.watchFile
, which uses stat polling, but it is slower and\nless reliable.\n\n
On Linux and OS X systems, fs.watch()
resolves the path to an [inode][] and\nwatches the inode. If the watched path is deleted and recreated, it is assigned\na new inode. The watch will emit an event for the delete but will continue\nwatching the original inode. Events for the new inode will not be emitted.\nThis is expected behavior.\n\n
Providing filename
argument in the callback is only supported on Linux and\nWindows. Even on supported platforms, filename
is not always guaranteed to\nbe provided. Therefore, don't assume that filename
argument is always\nprovided in the callback, and have some fallback logic if it is null.\n\n
fs.watch('somedir', (event, filename) => {\n console.log(`event is: ${event}`);\n if (filename) {\n console.log(`filename provided: ${filename}`);\n } else {\n console.log('filename not provided');\n }\n});
\n"
}
]
}
]
},
{
"textRaw": "fs.watchFile(filename[, options], listener)",
"type": "method",
"name": "watchFile",
"signatures": [
{
"params": [
{
"textRaw": "`filename` {String | Buffer} ",
"name": "filename",
"type": "String | Buffer"
},
{
"textRaw": "`options` {Object} ",
"options": [
{
"textRaw": "`persistent` {Boolean} ",
"name": "persistent",
"type": "Boolean"
},
{
"textRaw": "`interval` {Integer} ",
"name": "interval",
"type": "Integer"
}
],
"name": "options",
"type": "Object",
"optional": true
},
{
"textRaw": "`listener` {Function} ",
"name": "listener",
"type": "Function"
}
]
},
{
"params": [
{
"name": "filename"
},
{
"name": "options",
"optional": true
},
{
"name": "listener"
}
]
}
],
"desc": "Watch for changes on filename
. The callback listener
will be called each\ntime the file is accessed.\n\n
The options
argument may be omitted. If provided, it should be an object. The\noptions
object may contain a boolean named persistent
that indicates\nwhether the process should continue to run as long as files are being watched.\nThe options
object may specify an interval
property indicating how often the\ntarget should be polled in milliseconds. The default is\n{ persistent: true, interval: 5007 }
.\n\n
The listener
gets two arguments the current stat object and the previous\nstat object:\n\n
fs.watchFile('message.text', (curr, prev) => {\n console.log(`the current mtime is: ${curr.mtime}`);\n console.log(`the previous mtime was: ${prev.mtime}`);\n});
\nThese stat objects are instances of fs.Stat
.\n\n
If you want to be notified when the file was modified, not just accessed,\nyou need to compare curr.mtime
and prev.mtime
.\n\n
Note: when an fs.watchFile
operation results in an ENOENT
error, it will\n invoke the listener once, with all the fields zeroed (or, for dates, the Unix\n Epoch). In Windows, blksize
and blocks
fields will be undefined
, instead\n of zero. If the file is created later on, the listener will be called again,\n with the latest stat objects. This is a change in functionality since v0.10.\n\n
Note: [fs.watch()
][] is more efficient than fs.watchFile
and fs.unwatchFile
.\nfs.watch
should be used instead of fs.watchFile
and fs.unwatchFile
\nwhen possible.\n\n
Write buffer
to the file specified by fd
.\n\n
offset
and length
determine the part of the buffer to be written.\n\n
position
refers to the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number'
, the data will be written\nat the current position. See pwrite(2).\n\n
The callback will be given three arguments (err, written, buffer)
where\nwritten
specifies how many bytes were written from buffer
.\n\n
Note that it is unsafe to use fs.write
multiple times on the same file\nwithout waiting for the callback. For this scenario,\nfs.createWriteStream
is strongly recommended.\n\n
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.\n\n
\n" }, { "textRaw": "fs.write(fd, data[, position[, encoding]], callback)", "type": "method", "name": "write", "signatures": [ { "params": [ { "textRaw": "`fd` {Integer} ", "name": "fd", "type": "Integer" }, { "textRaw": "`data` {String | Buffer} ", "name": "data", "type": "String | Buffer" }, { "textRaw": "`position` {Integer} ", "name": "position", "type": "Integer", "optional": true }, { "textRaw": "`encoding` {String} ", "name": "encoding", "type": "String", "optional": true }, { "textRaw": "`callback` {Function} ", "name": "callback", "type": "Function" } ] }, { "params": [ { "name": "fd" }, { "name": "data" }, { "name": "position", "optional": true }, { "name": "encoding", "optional": true }, { "name": "callback" } ] } ], "desc": "Write data
to the file specified by fd
. If data
is not a Buffer instance\nthen the value will be coerced to a string.\n\n
position
refers to the offset from the beginning of the file where this data\nshould be written. If typeof position !== 'number'
the data will be written at\nthe current position. See pwrite(2).\n\n
encoding
is the expected string encoding.\n\n
The callback will receive the arguments (err, written, string)
where written
\nspecifies how many bytes the passed string required to be written. Note that\nbytes written is not the same as string characters. See [Buffer.byteLength
][].\n\n
Unlike when writing buffer
, the entire string must be written. No substring\nmay be specified. This is because the byte offset of the resulting data may not\nbe the same as the string offset.\n\n
Note that it is unsafe to use fs.write
multiple times on the same file\nwithout waiting for the callback. For this scenario,\nfs.createWriteStream
is strongly recommended.\n\n
On Linux, positional writes don't work when the file is opened in append mode.\nThe kernel ignores the position argument and always appends the data to\nthe end of the file.\n\n
\n" }, { "textRaw": "fs.writeFile(file, data[, options], callback)", "type": "method", "name": "writeFile", "signatures": [ { "params": [ { "textRaw": "`file` {String | Buffer | Integer} filename or file descriptor ", "name": "file", "type": "String | Buffer | Integer", "desc": "filename or file descriptor" }, { "textRaw": "`data` {String | Buffer} ", "name": "data", "type": "String | Buffer" }, { "textRaw": "`options` {Object | String} ", "options": [ { "textRaw": "`encoding` {String | Null} default = `'utf8'` ", "name": "encoding", "type": "String | Null", "desc": "default = `'utf8'`" }, { "textRaw": "`mode` {Integer} default = `0o666` ", "name": "mode", "type": "Integer", "desc": "default = `0o666`" }, { "textRaw": "`flag` {String} default = `'w'` ", "name": "flag", "type": "String", "desc": "default = `'w'`" } ], "name": "options", "type": "Object | String", "optional": true }, { "textRaw": "`callback` {Function} ", "name": "callback", "type": "Function" } ] }, { "params": [ { "name": "file" }, { "name": "data" }, { "name": "options", "optional": true }, { "name": "callback" } ] } ], "desc": "Asynchronously writes data to a file, replacing the file if it already exists.\ndata
can be a string or a buffer.\n\n
The encoding
option is ignored if data
is a buffer. It defaults\nto 'utf8'
.\n\n
Example:\n\n
\nfs.writeFile('message.txt', 'Hello Node.js', (err) => {\n if (err) throw err;\n console.log('It\\'s saved!');\n});
\nIf options
is a string, then it specifies the encoding. Example:\n\n
fs.writeFile('message.txt', 'Hello Node.js', 'utf8', callback);
\nAny specified file descriptor has to support writing.\n\n
\nNote that it is unsafe to use fs.writeFile
multiple times on the same file\nwithout waiting for the callback. For this scenario,\nfs.createWriteStream
is strongly recommended.\n\n
Note: Specified file descriptors will not be closed automatically.\n\n
\n" }, { "textRaw": "fs.writeFileSync(file, data[, options])", "type": "method", "name": "writeFileSync", "signatures": [ { "params": [ { "textRaw": "`file` {String | Buffer | Integer} filename or file descriptor ", "name": "file", "type": "String | Buffer | Integer", "desc": "filename or file descriptor" }, { "textRaw": "`data` {String | Buffer} ", "name": "data", "type": "String | Buffer" }, { "textRaw": "`options` {Object | String} ", "options": [ { "textRaw": "`encoding` {String | Null} default = `'utf8'` ", "name": "encoding", "type": "String | Null", "desc": "default = `'utf8'`" }, { "textRaw": "`mode` {Integer} default = `0o666` ", "name": "mode", "type": "Integer", "desc": "default = `0o666`" }, { "textRaw": "`flag` {String} default = `'w'` ", "name": "flag", "type": "String", "desc": "default = `'w'`" } ], "name": "options", "type": "Object | String", "optional": true } ] }, { "params": [ { "name": "file" }, { "name": "data" }, { "name": "options", "optional": true } ] } ], "desc": "The synchronous version of [fs.writeFile()
][]. Returns undefined
.\n\n
Synchronous versions of [fs.write()
][]. Returns the number of bytes written.\n\n
Synchronous versions of [fs.write()
][]. Returns the number of bytes written.\n\n
To use the HTTP server and client one must require('http')
.\n\n
The HTTP interfaces in Node.js are designed to support many features\nof the protocol which have been traditionally difficult to use.\nIn particular, large, possibly chunk-encoded, messages. The interface is\ncareful to never buffer entire requests or responses--the\nuser is able to stream data.\n\n
\nHTTP message headers are represented by an object like this:\n\n
\n{ 'content-length': '123',\n 'content-type': 'text/plain',\n 'connection': 'keep-alive',\n 'host': 'mysite.com',\n 'accept': '*/*' }
\nKeys are lowercased. Values are not modified.\n\n
\nIn order to support the full spectrum of possible HTTP applications, Node.js's\nHTTP API is very low-level. It deals with stream handling and message\nparsing only. It parses a message into headers and body but it does not\nparse the actual headers or the body.\n\n
\nSee [message.headers
][] for details on how duplicate headers are handled.\n\n
The raw headers as they were received are retained in the rawHeaders
\nproperty, which is an array of [key, value, key2, value2, ...]
. For\nexample, the previous message header object might have a rawHeaders
\nlist like the following:\n\n
[ 'ConTent-Length', '123456',\n 'content-LENGTH', '123',\n 'content-type', 'text/plain',\n 'CONNECTION', 'keep-alive',\n 'Host', 'mysite.com',\n 'accepT', '*/*' ]
\n",
"classes": [
{
"textRaw": "Class: http.Agent",
"type": "class",
"name": "http.Agent",
"desc": "The HTTP Agent is used for pooling sockets used in HTTP client\nrequests.\n\n
\nThe HTTP Agent also defaults client requests to using\nConnection:keep-alive. If no pending HTTP requests are waiting on a\nsocket to become free the socket is closed. This means that Node.js's\npool has the benefit of keep-alive when under load but still does not\nrequire developers to manually close the HTTP clients using\nKeepAlive.\n\n
\nIf you opt into using HTTP KeepAlive, you can create an Agent object\nwith that flag set to true
. (See the [constructor options][].)\nThen, the Agent will keep unused sockets in a pool for later use. They\nwill be explicitly marked so as to not keep the Node.js process running.\nHowever, it is still a good idea to explicitly [destroy()
][] KeepAlive\nagents when they are no longer in use, so that the Sockets will be shut\ndown.\n\n
Sockets are removed from the agent's pool when the socket emits either\na 'close'
event or a special 'agentRemove'
event. This means that if\nyou intend to keep one HTTP request open for a long time and don't\nwant it to stay in the pool you can do something along the lines of:\n\n
http.get(options, (res) => {\n // Do stuff\n}).on('socket', (socket) => {\n socket.emit('agentRemove');\n});
\nAlternatively, you could just opt out of pooling entirely using\nagent:false
:\n\n
http.get({\n hostname: 'localhost',\n port: 80,\n path: '/',\n agent: false // create a new agent just for this one request\n}, (res) => {\n // Do stuff with response\n})
\n",
"methods": [
{
"textRaw": "agent.createConnection(options[, callback])",
"type": "method",
"name": "createConnection",
"desc": "Produces a socket/stream to be used for HTTP requests.\n\n
\nBy default, this function is the same as [net.createConnection()
][]. However,\ncustom Agents may override this method in case greater flexibility is desired.\n\n
A socket/stream can be supplied in one of two ways: by returning the\nsocket/stream from this function, or by passing the socket/stream to callback
.\n\n
callback
has a signature of (err, stream)
.\n\n
Destroy any sockets that are currently in use by the agent.\n\n
\nIt is usually not necessary to do this. However, if you are using an\nagent with KeepAlive enabled, then it is best to explicitly shut down\nthe agent when you know that it will no longer be used. Otherwise,\nsockets may hang open for quite a long time before the server\nterminates them.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "agent.getName(options)", "type": "method", "name": "getName", "desc": "Get a unique name for a set of request options, to determine whether a\nconnection can be reused. In the http agent, this returns\nhost:port:localAddress
. In the https agent, the name includes the\nCA, cert, ciphers, and other HTTPS/TLS-specific options that determine\nsocket reusability.\n\n
Options:\n\n
\nhost
: A domain name or IP address of the server to issue the request to.port
: Port of remote server.localAddress
: Local interface to bind for network connections when issuing\nthe request.An object which contains arrays of sockets currently awaiting use by\nthe Agent when HTTP KeepAlive is used. Do not modify.\n\n
\n" }, { "textRaw": "agent.maxFreeSockets", "name": "maxFreeSockets", "desc": "By default set to 256. For Agents supporting HTTP KeepAlive, this\nsets the maximum number of sockets that will be left open in the free\nstate.\n\n
\n" }, { "textRaw": "agent.maxSockets", "name": "maxSockets", "desc": "By default set to Infinity. Determines how many concurrent sockets the agent\ncan have open per origin. Origin is either a 'host:port' or\n'host:port:localAddress' combination.\n\n
\n" }, { "textRaw": "agent.requests", "name": "requests", "desc": "An object which contains queues of requests that have not yet been assigned to\nsockets. Do not modify.\n\n
\n" }, { "textRaw": "agent.sockets", "name": "sockets", "desc": "An object which contains arrays of sockets currently in use by the\nAgent. Do not modify.\n\n
\n" } ], "signatures": [ { "params": [ { "textRaw": "`options` {Object} Set of configurable options to set on the agent. Can have the following fields: ", "options": [ { "textRaw": "`keepAlive` {Boolean} Keep sockets around in a pool to be used by other requests in the future. Default = `false` ", "name": "keepAlive", "type": "Boolean", "desc": "Keep sockets around in a pool to be used by other requests in the future. Default = `false`" }, { "textRaw": "`keepAliveMsecs` {Integer} When using HTTP KeepAlive, how often to send TCP KeepAlive packets over sockets being kept alive. Default = `1000`. Only relevant if `keepAlive` is set to `true`. ", "name": "keepAliveMsecs", "type": "Integer", "desc": "When using HTTP KeepAlive, how often to send TCP KeepAlive packets over sockets being kept alive. Default = `1000`. Only relevant if `keepAlive` is set to `true`." }, { "textRaw": "`maxSockets` {Number} Maximum number of sockets to allow per host. Default = `Infinity`. ", "name": "maxSockets", "type": "Number", "desc": "Maximum number of sockets to allow per host. Default = `Infinity`." }, { "textRaw": "`maxFreeSockets` {Number} Maximum number of sockets to leave open in a free state. Only relevant if `keepAlive` is set to `true`. Default = `256`. ", "name": "maxFreeSockets", "type": "Number", "desc": "Maximum number of sockets to leave open in a free state. Only relevant if `keepAlive` is set to `true`. Default = `256`." } ], "name": "options", "type": "Object", "desc": "Set of configurable options to set on the agent. Can have the following fields:", "optional": true } ], "desc": "The default [http.globalAgent
][] that is used by [http.request()
][] has all\nof these values set to their respective defaults.\n\n
To configure any of them, you must create your own [http.Agent
][] object.\n\n
const http = require('http');\nvar keepAliveAgent = new http.Agent({ keepAlive: true });\noptions.agent = keepAliveAgent;\nhttp.request(options, onResponseCallback);
\n"
},
{
"params": [
{
"name": "options",
"optional": true
}
],
"desc": "The default [http.globalAgent
][] that is used by [http.request()
][] has all\nof these values set to their respective defaults.\n\n
To configure any of them, you must create your own [http.Agent
][] object.\n\n
const http = require('http');\nvar keepAliveAgent = new http.Agent({ keepAlive: true });\noptions.agent = keepAliveAgent;\nhttp.request(options, onResponseCallback);
\n"
}
]
},
{
"textRaw": "Class: http.ClientRequest",
"type": "class",
"name": "http.ClientRequest",
"desc": "This object is created internally and returned from [http.request()
][]. It\nrepresents an in-progress request whose header has already been queued. The\nheader is still mutable using the setHeader(name, value)
, getHeader(name)
,\nremoveHeader(name)
API. The actual header will be sent along with the first\ndata chunk or when closing the connection.\n\n
To get the response, add a listener for 'response'
to the request object.\n'response'
will be emitted from the request object when the response\nheaders have been received. The 'response'
event is executed with one\nargument which is an instance of [http.IncomingMessage
][].\n\n
During the 'response'
event, one can add listeners to the\nresponse object; particularly to listen for the 'data'
event.\n\n
If no 'response'
handler is added, then the response will be\nentirely discarded. However, if you add a 'response'
event handler,\nthen you must consume the data from the response object, either by\ncalling response.read()
whenever there is a 'readable'
event, or\nby adding a 'data'
handler, or by calling the .resume()
method.\nUntil the data is consumed, the 'end'
event will not fire. Also, until\nthe data is read it will consume memory that can eventually lead to a\n'process out of memory' error.\n\n
Note: Node.js does not check whether Content-Length and the length of the body\nwhich has been transmitted are equal or not.\n\n
\nThe request implements the [Writable Stream][] interface. This is an\n[EventEmitter
][] with the following events:\n\n
function () { }
\n\n
Emitted when the request has been aborted by the client. This event is only\nemitted on the first call to abort()
.\n\n
function (request, response) { }
\n\n
Emitted each time a request with an http Expect header is received, where the\nvalue is not 100-continue. If this event isn't listened for, the server will\nautomatically respond with a 417 Expectation Failed as appropriate.\n\n
\nNote that when this event is emitted and handled, the request
event will\nnot be emitted.\n\n
function (response, socket, head) { }
\n\n
Emitted each time a server responds to a request with a CONNECT
method. If this\nevent isn't being listened for, clients receiving a CONNECT
method will have\ntheir connections closed.\n\n
A client server pair that show you how to listen for the 'connect'
event.\n\n
const http = require('http');\nconst net = require('net');\nconst url = require('url');\n\n// Create an HTTP tunneling proxy\nvar proxy = http.createServer( (req, res) => {\n res.writeHead(200, {'Content-Type': 'text/plain'});\n res.end('okay');\n});\nproxy.on('connect', (req, cltSocket, head) => {\n // connect to an origin server\n var srvUrl = url.parse(`http://${req.url}`);\n var srvSocket = net.connect(srvUrl.port, srvUrl.hostname, () => {\n cltSocket.write('HTTP/1.1 200 Connection Established\\r\\n' +\n 'Proxy-agent: Node.js-Proxy\\r\\n' +\n '\\r\\n');\n srvSocket.write(head);\n srvSocket.pipe(cltSocket);\n cltSocket.pipe(srvSocket);\n });\n});\n\n// now that proxy is running\nproxy.listen(1337, '127.0.0.1', () => {\n\n // make a request to a tunneling proxy\n var options = {\n port: 1337,\n hostname: '127.0.0.1',\n method: 'CONNECT',\n path: 'www.google.com:80'\n };\n\n var req = http.request(options);\n req.end();\n\n req.on('connect', (res, socket, head) => {\n console.log('got connected!');\n\n // make a request over an HTTP tunnel\n socket.write('GET / HTTP/1.1\\r\\n' +\n 'Host: www.google.com:80\\r\\n' +\n 'Connection: close\\r\\n' +\n '\\r\\n');\n socket.on('data', (chunk) => {\n console.log(chunk.toString());\n });\n socket.on('end', () => {\n proxy.close();\n });\n });\n});
\n",
"params": []
},
{
"textRaw": "Event: 'continue'",
"type": "event",
"name": "continue",
"desc": "function () { }
\n\n
Emitted when the server sends a '100 Continue' HTTP response, usually because\nthe request contained 'Expect: 100-continue'. This is an instruction that\nthe client should send the request body.\n\n
\n", "params": [] }, { "textRaw": "Event: 'response'", "type": "event", "name": "response", "desc": "function (response) { }
\n\n
Emitted when a response is received to this request. This event is emitted only\nonce. The response
argument will be an instance of [http.IncomingMessage
][].\n\n
function (socket) { }
\n\n
Emitted after a socket is assigned to this request.\n\n
\n", "params": [] }, { "textRaw": "Event: 'upgrade'", "type": "event", "name": "upgrade", "desc": "function (response, socket, head) { }
\n\n
Emitted each time a server responds to a request with an upgrade. If this\nevent isn't being listened for, clients receiving an upgrade header will have\ntheir connections closed.\n\n
\nA client server pair that show you how to listen for the 'upgrade'
event.\n\n
const http = require('http');\n\n// Create an HTTP server\nvar srv = http.createServer( (req, res) => {\n res.writeHead(200, {'Content-Type': 'text/plain'});\n res.end('okay');\n});\nsrv.on('upgrade', (req, socket, head) => {\n socket.write('HTTP/1.1 101 Web Socket Protocol Handshake\\r\\n' +\n 'Upgrade: WebSocket\\r\\n' +\n 'Connection: Upgrade\\r\\n' +\n '\\r\\n');\n\n socket.pipe(socket); // echo back\n});\n\n// now that server is running\nsrv.listen(1337, '127.0.0.1', () => {\n\n // make a request\n var options = {\n port: 1337,\n hostname: '127.0.0.1',\n headers: {\n 'Connection': 'Upgrade',\n 'Upgrade': 'websocket'\n }\n };\n\n var req = http.request(options);\n req.end();\n\n req.on('upgrade', (res, socket, upgradeHead) => {\n console.log('got upgraded!');\n socket.end();\n process.exit(0);\n });\n});
\n",
"params": []
}
],
"methods": [
{
"textRaw": "request.abort()",
"type": "method",
"name": "abort",
"desc": "Marks the request as aborting. Calling this will cause remaining data\nin the response to be dropped and the socket to be destroyed.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "request.end([data][, encoding][, callback])", "type": "method", "name": "end", "desc": "Finishes sending the request. If any parts of the body are\nunsent, it will flush them to the stream. If the request is\nchunked, this will send the terminating '0\\r\\n\\r\\n'
.\n\n
If data
is specified, it is equivalent to calling\n[response.write(data, encoding)
][] followed by request.end(callback)
.\n\n
If callback
is specified, it will be called when the request stream\nis finished.\n\n
Flush the request headers.\n\n
\nFor efficiency reasons, Node.js normally buffers the request headers until you\ncall request.end()
or write the first chunk of request data. It then tries\nhard to pack the request headers and data into a single TCP packet.\n\n
That's usually what you want (it saves a TCP round-trip) but not when the first\ndata isn't sent until possibly much later. request.flushHeaders()
lets you bypass\nthe optimization and kickstart the request.\n\n
Once a socket is assigned to this request and is connected\n[socket.setNoDelay()
][] will be called.\n\n
Once a socket is assigned to this request and is connected\n[socket.setKeepAlive()
][] will be called.\n\n
Once a socket is assigned to this request and is connected\n[socket.setTimeout()
][] will be called.\n\n
timeout
{Number} Milliseconds before a request is considered to be timed out.callback
{Function} Optional function to be called when a timeout occurs. Same as binding to the timeout
event.Sends a chunk of the body. By calling this method\nmany times, the user can stream a request body to a\nserver--in that case it is suggested to use the\n['Transfer-Encoding', 'chunked']
header line when\ncreating the request.\n\n
The chunk
argument should be a [Buffer
][] or a string.\n\n
The encoding
argument is optional and only applies when chunk
is a string.\nDefaults to 'utf8'
.\n\n
The callback
argument is optional and will be called when this chunk of data\nis flushed.\n\n
Returns request
.\n\n
This class inherits from [net.Server
][] and has the following additional events:\n\n
function (request, response) { }
\n\n
Emitted each time a request with an http Expect: 100-continue is received.\nIf this event isn't listened for, the server will automatically respond\nwith a 100 Continue as appropriate.\n\n
\nHandling this event involves calling [response.writeContinue()
][] if the client\nshould continue to send the request body, or generating an appropriate HTTP\nresponse (e.g., 400 Bad Request) if the client should not continue to send the\nrequest body.\n\n
Note that when this event is emitted and handled, the 'request'
event will\nnot be emitted.\n\n
function (exception, socket) { }
\n\n
If a client connection emits an 'error'
event, it will be forwarded here.\nListener of this event is responsible for closing/destroying the underlying\nsocket. For example, one may wish to more gracefully close the socket with an\nHTTP '400 Bad Request' response instead of abruptly severing the connection.\n\n
Default behavior is to destroy the socket immediately on malformed request.\n\n
\nsocket
is the [net.Socket
][] object that the error originated from.\n\n
const http = require('http');\n\nconst server = http.createServer((req, res) => {\n res.end();\n});\nserver.on('clientError', (err, socket) => {\n socket.end('HTTP/1.1 400 Bad Request\\r\\n\\r\\n');\n});\nserver.listen(8000);
\nWhen the 'clientError'
event occurs, there is no request
or response
\nobject, so any HTTP response sent, including response headers and payload,\nmust be written directly to the socket
object. Care must be taken to\nensure the response is a properly formatted HTTP response message.\n\n
function () { }
\n\n
Emitted when the server closes.\n\n
\n", "params": [] }, { "textRaw": "Event: 'connect'", "type": "event", "name": "connect", "desc": "function (request, socket, head) { }
\n\n
Emitted each time a client requests a http CONNECT
method. If this event isn't\nlistened for, then clients requesting a CONNECT
method will have their\nconnections closed.\n\n
request
is the arguments for the http request, as it is in the request\nevent.socket
is the network socket between the server and client.head
is an instance of Buffer, the first packet of the tunneling stream,\nthis may be empty.After this event is emitted, the request's socket will not have a 'data'
\nevent listener, meaning you will need to bind to it in order to handle data\nsent to the server on that socket.\n\n
function (socket) { }
\n\n
When a new TCP stream is established. socket
is an object of type\n[net.Socket
][]. Usually users will not want to access this event. In\nparticular, the socket will not emit 'readable'
events because of how\nthe protocol parser attaches to the socket. The socket
can also be\naccessed at request.connection
.\n\n
function (request, response) { }
\n\n
Emitted each time there is a request. Note that there may be multiple requests\nper connection (in the case of keep-alive connections).\n request
is an instance of [http.IncomingMessage
][] and response
is\nan instance of [http.ServerResponse
][].\n\n
function (request, socket, head) { }
\n\n
Emitted each time a client requests a http upgrade. If this event isn't\nlistened for, then clients requesting an upgrade will have their connections\nclosed.\n\n
\nrequest
is the arguments for the http request, as it is in the request\nevent.socket
is the network socket between the server and client.head
is an instance of Buffer, the first packet of the upgraded stream,\nthis may be empty.After this event is emitted, the request's socket will not have a 'data'
\nevent listener, meaning you will need to bind to it in order to handle data\nsent to the server on that socket.\n\n
Stops the server from accepting new connections. See [net.Server.close()
][].\n\n
The handle
object can be set to either a server or socket (anything\nwith an underlying _handle
member), or a {fd: <n>}
object.\n\n
This will cause the server to accept connections on the specified\nhandle, but it is presumed that the file descriptor or handle has\nalready been bound to a port or domain socket.\n\n
\nListening on a file descriptor is not supported on Windows.\n\n
\nThis function is asynchronous. The last parameter callback
will be added as\na listener for the 'listening'
event. See also [net.Server.listen()
][].\n\n
Returns server
.\n\n
Start a UNIX socket server listening for connections on the given path
.\n\n
This function is asynchronous. The last parameter callback
will be added as\na listener for the 'listening'
event. See also [net.Server.listen(path)
][].\n\n
Begin accepting connections on the specified port
and hostname
. If the\nhostname
is omitted, the server will accept connections on any IPv6 address\n(::
) when IPv6 is available, or any IPv4 address (0.0.0.0
) otherwise. A\nport value of zero will assign a random port.\n\n
To listen to a unix socket, supply a filename instead of port and hostname.\n\n
\nBacklog is the maximum length of the queue of pending connections.\nThe actual length will be determined by your OS through sysctl settings such as\ntcp_max_syn_backlog
and somaxconn
on linux. The default value of this\nparameter is 511 (not 512).\n\n
This function is asynchronous. The last parameter callback
will be added as\na listener for the 'listening'
event. See also [net.Server.listen(port)
][].\n\n
Sets the timeout value for sockets, and emits a 'timeout'
event on\nthe Server object, passing the socket as an argument, if a timeout\noccurs.\n\n
If there is a 'timeout'
event listener on the Server object, then it\nwill be called with the timed-out socket as an argument.\n\n
By default, the Server's timeout value is 2 minutes, and sockets are\ndestroyed automatically if they time out. However, if you assign a\ncallback to the Server's 'timeout'
event, then you are responsible\nfor handling socket timeouts.\n\n
Returns server
.\n\n
A Boolean indicating whether or not the server is listening for\nconnections.\n\n
\n" }, { "textRaw": "server.maxHeadersCount", "name": "maxHeadersCount", "desc": "Limits maximum incoming headers count, equal to 1000 by default. If set to 0 -\nno limit will be applied.\n\n
\n" }, { "textRaw": "`timeout` {Number} Default = 120000 (2 minutes) ", "type": "Number", "name": "timeout", "desc": "The number of milliseconds of inactivity before a socket is presumed\nto have timed out.\n\n
\nNote that the socket timeout logic is set up on connection, so\nchanging this value only affects new connections to the server, not\nany existing connections.\n\n
\nSet to 0 to disable any kind of automatic timeout behavior on incoming\nconnections.\n\n
\n", "shortDesc": "Default = 120000 (2 minutes)" } ] }, { "textRaw": "Class: http.ServerResponse", "type": "class", "name": "http.ServerResponse", "desc": "This object is created internally by a HTTP server--not by the user. It is\npassed as the second parameter to the 'request'
event.\n\n
The response implements, but does not inherit from, the [Writable Stream][]\ninterface. This is an [EventEmitter
][] with the following events:\n\n
function () { }
\n\n
Indicates that the underlying connection was terminated before\n[response.end()
][] was called or able to flush.\n\n
function () { }
\n\n
Emitted when the response has been sent. More specifically, this event is\nemitted when the last segment of the response headers and body have been\nhanded off to the operating system for transmission over the network. It\ndoes not imply that the client has received anything yet.\n\n
\nAfter this event, no more events will be emitted on the response object.\n\n
\n", "params": [] } ], "methods": [ { "textRaw": "response.addTrailers(headers)", "type": "method", "name": "addTrailers", "desc": "This method adds HTTP trailing headers (a header but at the end of the\nmessage) to the response.\n\n
\nTrailers will only be emitted if chunked encoding is used for the\nresponse; if it is not (e.g., if the request was HTTP/1.0), they will\nbe silently discarded.\n\n
\nNote that HTTP requires the Trailer
header to be sent if you intend to\nemit trailers, with a list of the header fields in its value. E.g.,\n\n
response.writeHead(200, { 'Content-Type': 'text/plain',\n 'Trailer': 'Content-MD5' });\nresponse.write(fileData);\nresponse.addTrailers({'Content-MD5': '7895bf4b8828b55ceaf47747b4bca667'});\nresponse.end();
\nAttempting to set a header field name or value that contains invalid characters\nwill result in a [TypeError
][] being thrown.\n\n
This method signals to the server that all of the response headers and body\nhave been sent; that server should consider this message complete.\nThe method, response.end()
, MUST be called on each response.\n\n
If data
is specified, it is equivalent to calling\n[response.write(data, encoding)
][] followed by response.end(callback)
.\n\n
If callback
is specified, it will be called when the response stream\nis finished.\n\n
Reads out a header that's already been queued but not sent to the client. Note\nthat the name is case insensitive. This can only be called before headers get\nimplicitly flushed.\n\n
\nExample:\n\n
\nvar contentType = response.getHeader('content-type');
\n",
"signatures": [
{
"params": [
{
"name": "name"
}
]
}
]
},
{
"textRaw": "response.removeHeader(name)",
"type": "method",
"name": "removeHeader",
"desc": "Removes a header that's queued for implicit sending.\n\n
\nExample:\n\n
\nresponse.removeHeader('Content-Encoding');
\n",
"signatures": [
{
"params": [
{
"name": "name"
}
]
}
]
},
{
"textRaw": "response.setHeader(name, value)",
"type": "method",
"name": "setHeader",
"desc": "Sets a single header value for implicit headers. If this header already exists\nin the to-be-sent headers, its value will be replaced. Use an array of strings\nhere if you need to send multiple headers with the same name.\n\n
\nExample:\n\n
\nresponse.setHeader('Content-Type', 'text/html');
\nor\n\n
\nresponse.setHeader('Set-Cookie', ['type=ninja', 'language=javascript']);
\nAttempting to set a header field name or value that contains invalid characters\nwill result in a [TypeError
][] being thrown.\n\n
When headers have been set with [response.setHeader()
][], they will be merged with\nany headers passed to [response.writeHead()
][], with the headers passed to\n[response.writeHead()
][] given precedence.\n\n
// returns content-type = text/plain\nconst server = http.createServer((req,res) => {\n res.setHeader('Content-Type', 'text/html');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, {'Content-Type': 'text/plain'});\n res.end('ok');\n});
\n",
"signatures": [
{
"params": [
{
"name": "name"
},
{
"name": "value"
}
]
}
]
},
{
"textRaw": "response.setTimeout(msecs, callback)",
"type": "method",
"name": "setTimeout",
"signatures": [
{
"params": [
{
"textRaw": "`msecs` {Number} ",
"name": "msecs",
"type": "Number"
},
{
"textRaw": "`callback` {Function} ",
"name": "callback",
"type": "Function"
}
]
},
{
"params": [
{
"name": "msecs"
},
{
"name": "callback"
}
]
}
],
"desc": "Sets the Socket's timeout value to msecs
. If a callback is\nprovided, then it is added as a listener on the 'timeout'
event on\nthe response object.\n\n
If no 'timeout'
listener is added to the request, the response, or\nthe server, then sockets are destroyed when they time out. If you\nassign a handler on the request, the response, or the server's\n'timeout'
events, then it is your responsibility to handle timed out\nsockets.\n\n
Returns response
.\n\n
If this method is called and [response.writeHead()
][] has not been called,\nit will switch to implicit header mode and flush the implicit headers.\n\n
This sends a chunk of the response body. This method may\nbe called multiple times to provide successive parts of the body.\n\n
\nchunk
can be a string or a buffer. If chunk
is a string,\nthe second parameter specifies how to encode it into a byte stream.\nBy default the encoding
is 'utf8'
. The last parameter callback
\nwill be called when this chunk of data is flushed.\n\n
Note: This is the raw HTTP body and has nothing to do with\nhigher-level multi-part body encodings that may be used.\n\n
\nThe first time [response.write()
][] is called, it will send the buffered\nheader information and the first body to the client. The second time\n[response.write()
][] is called, Node.js assumes you're going to be streaming\ndata, and sends that separately. That is, the response is buffered up to the\nfirst chunk of body.\n\n
Returns true
if the entire data was flushed successfully to the kernel\nbuffer. Returns false
if all or part of the data was queued in user memory.\n'drain'
will be emitted when the buffer is free again.\n\n
Sends a HTTP/1.1 100 Continue message to the client, indicating that\nthe request body should be sent. See the ['checkContinue'
][] event on Server
.\n\n
Sends a response header to the request. The status code is a 3-digit HTTP\nstatus code, like 404
. The last argument, headers
, are the response headers.\nOptionally one can give a human-readable statusMessage
as the second\nargument.\n\n
Example:\n\n
\nvar body = 'hello world';\nresponse.writeHead(200, {\n 'Content-Length': body.length,\n 'Content-Type': 'text/plain' });
\nThis method must only be called once on a message and it must\nbe called before [response.end()
][] is called.\n\n
If you call [response.write()
][] or [response.end()
][] before calling this,\nthe implicit/mutable headers will be calculated and call this function for you.\n\n
When headers have been set with [response.setHeader()
][], they will be merged with\nany headers passed to [response.writeHead()
][], with the headers passed to\n[response.writeHead()
][] given precedence.\n\n
// returns content-type = text/plain\nconst server = http.createServer((req,res) => {\n res.setHeader('Content-Type', 'text/html');\n res.setHeader('X-Foo', 'bar');\n res.writeHead(200, {'Content-Type': 'text/plain'});\n res.end('ok');\n});
\nNote that Content-Length is given in bytes not characters. The above example\nworks because the string 'hello world'
contains only single byte characters.\nIf the body contains higher coded characters then Buffer.byteLength()
\nshould be used to determine the number of bytes in a given encoding.\nAnd Node.js does not check whether Content-Length and the length of the body\nwhich has been transmitted are equal or not.\n\n
Attempting to set a header field name or value that contains invalid characters\nwill result in a [TypeError
][] being thrown.\n\n
Boolean value that indicates whether the response has completed. Starts\nas false
. After [response.end()
][] executes, the value will be true
.\n\n
Boolean (read-only). True if headers were sent, false otherwise.\n\n
\n" }, { "textRaw": "response.sendDate", "name": "sendDate", "desc": "When true, the Date header will be automatically generated and sent in\nthe response if it is not already present in the headers. Defaults to true.\n\n
\nThis should only be disabled for testing; HTTP requires the Date header\nin responses.\n\n
\n" }, { "textRaw": "response.statusCode", "name": "statusCode", "desc": "When using implicit headers (not calling [response.writeHead()
][] explicitly),\nthis property controls the status code that will be sent to the client when\nthe headers get flushed.\n\n
Example:\n\n
\nresponse.statusCode = 404;
\nAfter response header was sent to the client, this property indicates the\nstatus code which was sent out.\n\n
\n" }, { "textRaw": "response.statusMessage", "name": "statusMessage", "desc": "When using implicit headers (not calling [response.writeHead()
][] explicitly), this property\ncontrols the status message that will be sent to the client when the headers get\nflushed. If this is left as undefined
then the standard message for the status\ncode will be used.\n\n
Example:\n\n
\nresponse.statusMessage = 'Not found';
\nAfter response header was sent to the client, this property indicates the\nstatus message which was sent out.\n\n
\n" } ] }, { "textRaw": "Class: http.IncomingMessage", "type": "class", "name": "http.IncomingMessage", "desc": "An IncomingMessage
object is created by [http.Server
][] or\n[http.ClientRequest
][] and passed as the first argument to the 'request'
\nand 'response'
event respectively. It may be used to access response status,\nheaders and data.\n\n
It implements the [Readable Stream][] interface, as well as the\nfollowing additional events, methods, and properties.\n\n
\n", "events": [ { "textRaw": "Event: 'close'", "type": "event", "name": "close", "desc": "function () { }
\n\n
Indicates that the underlying connection was closed.\nJust like 'end'
, this event occurs only once per response.\n\n
The request/response headers object.\n\n
\nKey-value pairs of header names and values. Header names are lower-cased.\nExample:\n\n
\n// Prints something like:\n//\n// { 'user-agent': 'curl/7.22.0',\n// host: '127.0.0.1:8000',\n// accept: '*/*' }\nconsole.log(request.headers);
\nDuplicates in raw headers are handled in the following ways, depending on the\nheader name:\n\n
\nage
, authorization
, content-length
, content-type
,\netag
, expires
, from
, host
, if-modified-since
, if-unmodified-since
,\nlast-modified
, location
, max-forwards
, proxy-authorization
, referer
,\nretry-after
, or user-agent
are discarded.set-cookie
is always an array. Duplicates are added to the array.In case of server request, the HTTP version sent by the client. In the case of\nclient response, the HTTP version of the connected-to server.\nProbably either '1.1'
or '1.0'
.\n\n
Also message.httpVersionMajor
is the first integer and\nmessage.httpVersionMinor
is the second.\n\n
Only valid for request obtained from [http.Server
][].\n\n
The request method as a string. Read only. Example:\n'GET'
, 'DELETE'
.\n\n
The raw request/response headers list exactly as they were received.\n\n
\nNote that the keys and values are in the same list. It is not a\nlist of tuples. So, the even-numbered offsets are key values, and the\nodd-numbered offsets are the associated values.\n\n
\nHeader names are not lowercased, and duplicates are not merged.\n\n
\n// Prints something like:\n//\n// [ 'user-agent',\n// 'this is invalid because there can be only one',\n// 'User-Agent',\n// 'curl/7.22.0',\n// 'Host',\n// '127.0.0.1:8000',\n// 'ACCEPT',\n// '*/*' ]\nconsole.log(request.rawHeaders);
\n"
},
{
"textRaw": "message.rawTrailers",
"name": "rawTrailers",
"desc": "The raw request/response trailer keys and values exactly as they were\nreceived. Only populated at the 'end'
event.\n\n
Only valid for response obtained from [http.ClientRequest
][].\n\n
The 3-digit HTTP response status code. E.G. 404
.\n\n
Only valid for response obtained from [http.ClientRequest
][].\n\n
The HTTP response status message (reason phrase). E.G. OK
or Internal Server Error
.\n\n
The [net.Socket
][] object associated with the connection.\n\n
With HTTPS support, use [request.socket.getPeerCertificate()
][] to obtain the\nclient's authentication details.\n\n
The request/response trailers object. Only populated at the 'end'
event.\n\n
Only valid for request obtained from [http.Server
][].\n\n
Request URL string. This contains only the URL that is\npresent in the actual HTTP request. If the request is:\n\n
\nGET /status?name=ryan HTTP/1.1\\r\\n\nAccept: text/plain\\r\\n\n\\r\\n
\nThen request.url
will be:\n\n
'/status?name=ryan'
\nIf you would like to parse the URL into its parts, you can use\nrequire('url').parse(request.url)
. Example:\n\n
$ node\n> require('url').parse('/status?name=ryan')\n{\n href: '/status?name=ryan',\n search: '?name=ryan',\n query: 'name=ryan',\n pathname: '/status'\n}
\nIf you would like to extract the params from the query string,\nyou can use the require('querystring').parse
function, or pass\ntrue
as the second argument to require('url').parse
. Example:\n\n
$ node\n> require('url').parse('/status?name=ryan', true)\n{\n href: '/status?name=ryan',\n search: '?name=ryan',\n query: {name: 'ryan'},\n pathname: '/status'\n}
\n"
}
],
"methods": [
{
"textRaw": "message.setTimeout(msecs, callback)",
"type": "method",
"name": "setTimeout",
"signatures": [
{
"params": [
{
"textRaw": "`msecs` {Number} ",
"name": "msecs",
"type": "Number"
},
{
"textRaw": "`callback` {Function} ",
"name": "callback",
"type": "Function"
}
]
},
{
"params": [
{
"name": "msecs"
},
{
"name": "callback"
}
]
}
],
"desc": "Calls message.connection.setTimeout(msecs, callback)
.\n\n
Returns message
.\n\n
A list of the HTTP methods that are supported by the parser.\n\n
\n" }, { "textRaw": "`STATUS_CODES` {Object} ", "type": "Object", "name": "STATUS_CODES", "desc": "A collection of all the standard HTTP response status codes, and the\nshort description of each. For example, http.STATUS_CODES[404] === 'Not\nFound'
.\n\n
Global instance of Agent which is used as the default for all http client\nrequests.\n\n
\n" } ], "methods": [ { "textRaw": "http.createClient([port][, host])", "type": "method", "name": "createClient", "stability": 0, "stabilityText": "Deprecated: Use [`http.request()`][] instead.", "desc": "Constructs a new HTTP client. port
and host
refer to the server to be\nconnected to.\n\n
Returns a new instance of [http.Server
][].\n\n
The requestListener
is a function which is automatically\nadded to the 'request'
event.\n\n
Since most requests are GET requests without bodies, Node.js provides this\nconvenience method. The only difference between this method and [http.request()
][]\nis that it sets the method to GET and calls req.end()
automatically.\n\n
Example:\n\n
\nhttp.get('http://www.google.com/index.html', (res) => {\n console.log(`Got response: ${res.statusCode}`);\n // consume response body\n res.resume();\n}).on('error', (e) => {\n console.log(`Got error: ${e.message}`);\n});
\n",
"signatures": [
{
"params": [
{
"name": "options"
},
{
"name": "callback",
"optional": true
}
]
}
]
},
{
"textRaw": "http.request(options[, callback])",
"type": "method",
"name": "request",
"desc": "Node.js maintains several connections per server to make HTTP requests.\nThis function allows one to transparently issue requests.\n\n
\noptions
can be an object or a string. If options
is a string, it is\nautomatically parsed with [url.parse()
][].\n\n
Options:\n\n
\nprotocol
: Protocol to use. Defaults to 'http:'
.host
: A domain name or IP address of the server to issue the request to.\nDefaults to 'localhost'
.hostname
: Alias for host
. To support [url.parse()
][] hostname
is\npreferred over host
.family
: IP address family to use when resolving host
and hostname
.\nValid values are 4
or 6
. When unspecified, both IP v4 and v6 will be\nused.port
: Port of remote server. Defaults to 80.localAddress
: Local interface to bind for network connections.socketPath
: Unix Domain Socket (use one of host:port or socketPath).method
: A string specifying the HTTP request method. Defaults to 'GET'
.path
: Request path. Defaults to '/'
. Should include query string if any.\nE.G. '/index.html?page=12'
. An exception is thrown when the request path\ncontains illegal characters. Currently, only spaces are rejected but that\nmay change in the future.headers
: An object containing request headers.auth
: Basic authentication i.e. 'user:password'
to compute an\nAuthorization header.agent
: Controls [Agent
][] behavior. When an Agent is used request will\ndefault to Connection: keep-alive
. Possible values:undefined
(default): use [http.globalAgent
][] for this host and port.Agent
object: explicitly use the passed in Agent
.false
: opts out of connection pooling with an Agent, defaults request to\nConnection: close
.createConnection
: A function that produces a socket/stream to use for the\nrequest when the agent
option is not used. This can be used to avoid\ncreating a custom Agent class just to override the default createConnection
\nfunction. See [agent.createConnection()
][] for more details.The optional callback
parameter will be added as a one time listener for\nthe 'response'
event.\n\n
http.request()
returns an instance of the [http.ClientRequest
][]\nclass. The ClientRequest
instance is a writable stream. If one needs to\nupload a file with a POST request, then write to the ClientRequest
object.\n\n
Example:\n\n
\nvar postData = querystring.stringify({\n 'msg' : 'Hello World!'\n});\n\nvar options = {\n hostname: 'www.google.com',\n port: 80,\n path: '/upload',\n method: 'POST',\n headers: {\n 'Content-Type': 'application/x-www-form-urlencoded',\n 'Content-Length': postData.length\n }\n};\n\nvar req = http.request(options, (res) => {\n console.log(`STATUS: ${res.statusCode}`);\n console.log(`HEADERS: ${JSON.stringify(res.headers)}`);\n res.setEncoding('utf8');\n res.on('data', (chunk) => {\n console.log(`BODY: ${chunk}`);\n });\n res.on('end', () => {\n console.log('No more data in response.')\n })\n});\n\nreq.on('error', (e) => {\n console.log(`problem with request: ${e.message}`);\n});\n\n// write data to request body\nreq.write(postData);\nreq.end();
\nNote that in the example req.end()
was called. With http.request()
one\nmust always call req.end()
to signify that you're done with the request -\neven if there is no data being written to the request body.\n\n
If any error is encountered during the request (be that with DNS resolution,\nTCP level errors, or actual HTTP parse errors) an 'error'
event is emitted\non the returned request object. As with all 'error'
events, if no listeners\nare registered the error will be thrown.\n\n
There are a few special headers that should be noted.\n\n
\nSending a 'Connection: keep-alive' will notify Node.js that the connection to\nthe server should be persisted until the next request.
\nSending a 'Content-length' header will disable the default chunked encoding.
\nSending an 'Expect' header will immediately send the request headers.\nUsually, when sending 'Expect: 100-continue', you should both set a timeout\nand listen for the 'continue'
event. See RFC2616 Section 8.2.3 for more\ninformation.
Sending an Authorization header will override using the auth
option\nto compute basic authentication.
HTTPS is the HTTP protocol over TLS/SSL. In Node.js this is implemented as a\nseparate module.\n\n
\n", "classes": [ { "textRaw": "Class: https.Agent", "type": "class", "name": "https.Agent", "desc": "An Agent object for HTTPS similar to [http.Agent
][]. See [https.request()
][]\nfor more information.\n\n
This class is a subclass of tls.Server
and emits events same as\n[http.Server
][]. See [http.Server
][] for more information.\n\n
See [http.Server#setTimeout()
][].\n\n
See [http.Server#timeout
][].\n\n
Returns a new HTTPS web server object. The options
is similar to\n[tls.createServer()
][]. The requestListener
is a function which is\nautomatically added to the 'request'
event.\n\n
Example:\n\n
\n// curl -k https://localhost:8000/\nconst https = require('https');\nconst fs = require('fs');\n\nconst options = {\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem')\n};\n\nhttps.createServer(options, (req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n}).listen(8000);
\nOr\n\n
\nconst https = require('https');\nconst fs = require('fs');\n\nconst options = {\n pfx: fs.readFileSync('server.pfx')\n};\n\nhttps.createServer(options, (req, res) => {\n res.writeHead(200);\n res.end('hello world\\n');\n}).listen(8000);
\n",
"methods": [
{
"textRaw": "server.close([callback])",
"type": "method",
"name": "close",
"desc": "See [http.close()
][] for details.\n\n
See [http.listen()
][] for details.\n\n
See [http.listen()
][] for details.\n\n
Like [http.get()
][] but for HTTPS.\n\n
options
can be an object or a string. If options
is a string, it is\nautomatically parsed with [url.parse()
][].\n\n
Example:\n\n
\nconst https = require('https');\n\nhttps.get('https://encrypted.google.com/', (res) => {\n console.log('statusCode: ', res.statusCode);\n console.log('headers: ', res.headers);\n\n res.on('data', (d) => {\n process.stdout.write(d);\n });\n\n}).on('error', (e) => {\n console.error(e);\n});
\n",
"signatures": [
{
"params": [
{
"name": "options"
},
{
"name": "callback"
}
]
}
]
},
{
"textRaw": "https.request(options, callback)",
"type": "method",
"name": "request",
"desc": "Makes a request to a secure web server.\n\n
\noptions
can be an object or a string. If options
is a string, it is\nautomatically parsed with [url.parse()
][].\n\n
All options from [http.request()
][] are valid.\n\n
Example:\n\n
\nconst https = require('https');\n\nvar options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET'\n};\n\nvar req = https.request(options, (res) => {\n console.log('statusCode: ', res.statusCode);\n console.log('headers: ', res.headers);\n\n res.on('data', (d) => {\n process.stdout.write(d);\n });\n});\nreq.end();\n\nreq.on('error', (e) => {\n console.error(e);\n});
\nThe options argument has the following options\n\n
\nhost
: A domain name or IP address of the server to issue the request to.\nDefaults to 'localhost'
.hostname
: Alias for host
. To support url.parse()
hostname
is\npreferred over host
.family
: IP address family to use when resolving host
and hostname
.\nValid values are 4
or 6
. When unspecified, both IP v4 and v6 will be\nused.port
: Port of remote server. Defaults to 443.localAddress
: Local interface to bind for network connections.socketPath
: Unix Domain Socket (use one of host:port or socketPath).method
: A string specifying the HTTP request method. Defaults to 'GET'
.path
: Request path. Defaults to '/'
. Should include query string if any.\nE.G. '/index.html?page=12'
. An exception is thrown when the request path\ncontains illegal characters. Currently, only spaces are rejected but that\nmay change in the future.headers
: An object containing request headers.auth
: Basic authentication i.e. 'user:password'
to compute an\nAuthorization header.agent
: Controls [Agent
][] behavior. When an Agent is used request will\ndefault to Connection: keep-alive
. Possible values:undefined
(default): use [globalAgent
][] for this host and port.Agent
object: explicitly use the passed in Agent
.false
: opts out of connection pooling with an Agent, defaults request to\nConnection: close
.The following options from [tls.connect()
][] can also be specified. However, a\n[globalAgent
][] silently ignores these.\n\n
pfx
: Certificate, Private key and CA certificates to use for SSL. Default null
.key
: Private key to use for SSL. Default null
.passphrase
: A string of passphrase for the private key or pfx. Default null
.cert
: Public x509 certificate to use. Default null
.ca
: A string, [Buffer
][] or array of strings or [Buffer
][]s of trusted\ncertificates in PEM format. If this is omitted several well known "root"\nCAs will be used, like VeriSign. These are used to authorize connections.ciphers
: A string describing the ciphers to use or exclude. Consult\nhttps://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT for\ndetails on the format.rejectUnauthorized
: If true
, the server certificate is verified against\nthe list of supplied CAs. An 'error'
event is emitted if verification\nfails. Verification happens at the connection level, before the HTTP\nrequest is sent. Default true
.secureProtocol
: The SSL method to use, e.g. SSLv3_method
to force\nSSL version 3. The possible values depend on your installation of\nOpenSSL and are defined in the constant [SSL_METHODS
][].servername
: Servername for SNI (Server Name Indication) TLS extension.In order to specify these options, use a custom [Agent
][].\n\n
Example:\n\n
\nvar options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem')\n};\noptions.agent = new https.Agent(options);\n\nvar req = https.request(options, (res) => {\n ...\n}
\nAlternatively, opt out of connection pooling by not using an Agent
.\n\n
Example:\n\n
\nvar options = {\n hostname: 'encrypted.google.com',\n port: 443,\n path: '/',\n method: 'GET',\n key: fs.readFileSync('test/fixtures/keys/agent2-key.pem'),\n cert: fs.readFileSync('test/fixtures/keys/agent2-cert.pem'),\n agent: false\n};\n\nvar req = https.request(options, (res) => {\n ...\n}
\n",
"signatures": [
{
"params": [
{
"name": "options"
},
{
"name": "callback"
}
]
}
]
}
],
"properties": [
{
"textRaw": "https.globalAgent",
"name": "globalAgent",
"desc": "Global instance of [https.Agent
][] for all HTTPS client requests.\n\n
Node.js has a simple module loading system. In Node.js, files and modules are\nin one-to-one correspondence. As an example, foo.js
loads the module\ncircle.js
in the same directory.\n\n
The contents of foo.js
:\n\n
const circle = require('./circle.js');\nconsole.log( `The area of a circle of radius 4 is ${circle.area(4)}`);
\nThe contents of circle.js
:\n\n
const PI = Math.PI;\n\nexports.area = (r) => PI * r * r;\n\nexports.circumference = (r) => 2 * PI * r;
\nThe module circle.js
has exported the functions area()
and\ncircumference()
. To add functions and objects to the root of your module,\nyou can add them to the special exports
object.\n\n
Variables local to the module will be private, as though the module was wrapped\nin a function. In this example the variable PI
is private to circle.js
.\n\n
If you want the root of your module's export to be a function (such as a\nconstructor) or if you want to export a complete object in one assignment\ninstead of building it one property at a time, assign it to module.exports
\ninstead of exports
.\n\n
Below, bar.js
makes use of the square
module, which exports a constructor:\n\n
const square = require('./square.js');\nvar mySquare = square(2);\nconsole.log(`The area of my square is ${mySquare.area()}`);
\nThe square
module is defined in square.js
:\n\n
// assigning to exports will not modify module, must use module.exports\nmodule.exports = (width) => {\n return {\n area: () => width * width\n };\n}
\nThe module system is implemented in the require("module")
module.\n\n
When a file is run directly from Node.js, require.main
is set to its\nmodule
. That means that you can determine whether a file has been run\ndirectly by testing\n\n
require.main === module
\nFor a file foo.js
, this will be true
if run via node foo.js
, but\nfalse
if run by require('./foo')
.\n\n
Because module
provides a filename
property (normally equivalent to\n__filename
), the entry point of the current application can be obtained\nby checking require.main.filename
.\n\n
The semantics of Node.js's require()
function were designed to be general\nenough to support a number of reasonable directory structures. Package manager\nprograms such as dpkg
, rpm
, and npm
will hopefully find it possible to\nbuild native packages from Node.js modules without modification.\n\n
Below we give a suggested directory structure that could work:\n\n
\nLet's say that we wanted to have the folder at\n/usr/lib/node/<some-package>/<some-version>
hold the contents of a\nspecific version of a package.\n\n
Packages can depend on one another. In order to install package foo
, you\nmay have to install a specific version of package bar
. The bar
package\nmay itself have dependencies, and in some cases, these dependencies may even\ncollide or form cycles.\n\n
Since Node.js looks up the realpath
of any modules it loads (that is,\nresolves symlinks), and then looks for their dependencies in the node_modules
\nfolders as described here, this\nsituation is very simple to resolve with the following architecture:\n\n
/usr/lib/node/foo/1.2.3/
- Contents of the foo
package, version 1.2.3./usr/lib/node/bar/4.3.2/
- Contents of the bar
package that foo
\ndepends on./usr/lib/node/foo/1.2.3/node_modules/bar
- Symbolic link to\n/usr/lib/node/bar/4.3.2/
./usr/lib/node/bar/4.3.2/node_modules/*
- Symbolic links to the packages\nthat bar
depends on.Thus, even if a cycle is encountered, or if there are dependency\nconflicts, every module will be able to get a version of its dependency\nthat it can use.\n\n
\nWhen the code in the foo
package does require('bar')
, it will get the\nversion that is symlinked into /usr/lib/node/foo/1.2.3/node_modules/bar
.\nThen, when the code in the bar
package calls require('quux')
, it'll get\nthe version that is symlinked into\n/usr/lib/node/bar/4.3.2/node_modules/quux
.\n\n
Furthermore, to make the module lookup process even more optimal, rather\nthan putting packages directly in /usr/lib/node
, we could put them in\n/usr/lib/node_modules/<name>/<version>
. Then Node.js will not bother\nlooking for missing dependencies in /usr/node_modules
or /node_modules
.\n\n
In order to make modules available to the Node.js REPL, it might be useful to\nalso add the /usr/lib/node_modules
folder to the $NODE_PATH
environment\nvariable. Since the module lookups using node_modules
folders are all\nrelative, and based on the real path of the files making the calls to\nrequire()
, the packages themselves can be anywhere.\n\n
To get the exact filename that will be loaded when require()
is called, use\nthe require.resolve()
function.\n\n
Putting together all of the above, here is the high-level algorithm\nin pseudocode of what require.resolve does:\n\n
\nrequire(X) from module at path Y\n1. If X is a core module,\n a. return the core module\n b. STOP\n2. If X begins with './' or '/' or '../'\n a. LOAD_AS_FILE(Y + X)\n b. LOAD_AS_DIRECTORY(Y + X)\n3. LOAD_NODE_MODULES(X, dirname(Y))\n4. THROW "not found"\n\nLOAD_AS_FILE(X)\n1. If X is a file, load X as JavaScript text. STOP\n2. If X.js is a file, load X.js as JavaScript text. STOP\n3. If X.json is a file, parse X.json to a JavaScript Object. STOP\n4. If X.node is a file, load X.node as binary addon. STOP\n\nLOAD_AS_DIRECTORY(X)\n1. If X/package.json is a file,\n a. Parse X/package.json, and look for "main" field.\n b. let M = X + (json main field)\n c. LOAD_AS_FILE(M)\n2. If X/index.js is a file, load X/index.js as JavaScript text. STOP\n3. If X/index.json is a file, parse X/index.json to a JavaScript object. STOP\n4. If X/index.node is a file, load X/index.node as binary addon. STOP\n\nLOAD_NODE_MODULES(X, START)\n1. let DIRS=NODE_MODULES_PATHS(START)\n2. for each DIR in DIRS:\n a. LOAD_AS_FILE(DIR/X)\n b. LOAD_AS_DIRECTORY(DIR/X)\n\nNODE_MODULES_PATHS(START)\n1. let PARTS = path split(START)\n2. let I = count of PARTS - 1\n3. let DIRS = []\n4. while I >= 0,\n a. if PARTS[I] = "node_modules" CONTINUE\n c. DIR = path join(PARTS[0 .. I] + "node_modules")\n b. DIRS = DIRS + DIR\n c. let I = I - 1\n5. return DIRS
\n"
},
{
"textRaw": "Caching",
"name": "Caching",
"type": "misc",
"desc": "Modules are cached after the first time they are loaded. This means\n(among other things) that every call to require('foo')
will get\nexactly the same object returned, if it would resolve to the same file.\n\n
Multiple calls to require('foo')
may not cause the module code to be\nexecuted multiple times. This is an important feature. With it,\n"partially done" objects can be returned, thus allowing transitive\ndependencies to be loaded even when they would cause cycles.\n\n
If you want to have a module execute code multiple times, then export a\nfunction, and call that function.\n\n
\n", "miscs": [ { "textRaw": "Module Caching Caveats", "name": "Module Caching Caveats", "type": "misc", "desc": "Modules are cached based on their resolved filename. Since modules may\nresolve to a different filename based on the location of the calling\nmodule (loading from node_modules
folders), it is not a guarantee\nthat require('foo')
will always return the exact same object, if it\nwould resolve to different files.\n\n
Additionally, on case-insensitive file systems or operating systems, different\nresolved filenames can point to the same file, but the cache will still treat\nthem as different modules and will reload the file multiple times. For example,\nrequire('./foo')
and require('./FOO')
return two different objects,\nirrespective of whether or not ./foo
and ./FOO
are the same file.\n\n
Node.js has several modules compiled into the binary. These modules are\ndescribed in greater detail elsewhere in this documentation.\n\n
\nThe core modules are defined within Node.js's source and are located in the\nlib/
folder.\n\n
Core modules are always preferentially loaded if their identifier is\npassed to require()
. For instance, require('http')
will always\nreturn the built in HTTP module, even if there is a file by that name.\n\n
When there are circular require()
calls, a module might not have finished\nexecuting when it is returned.\n\n
Consider this situation:\n\n
\na.js
:\n\n
console.log('a starting');\nexports.done = false;\nconst b = require('./b.js');\nconsole.log('in a, b.done = %j', b.done);\nexports.done = true;\nconsole.log('a done');
\nb.js
:\n\n
console.log('b starting');\nexports.done = false;\nconst a = require('./a.js');\nconsole.log('in b, a.done = %j', a.done);\nexports.done = true;\nconsole.log('b done');
\nmain.js
:\n\n
console.log('main starting');\nconst a = require('./a.js');\nconst b = require('./b.js');\nconsole.log('in main, a.done=%j, b.done=%j', a.done, b.done);
\nWhen main.js
loads a.js
, then a.js
in turn loads b.js
. At that\npoint, b.js
tries to load a.js
. In order to prevent an infinite\nloop, an unfinished copy of the a.js
exports object is returned to the\nb.js
module. b.js
then finishes loading, and its exports
object is\nprovided to the a.js
module.\n\n
By the time main.js
has loaded both modules, they're both finished.\nThe output of this program would thus be:\n\n
$ node main.js\nmain starting\na starting\nb starting\nin b, a.done = false\nb done\nin a, b.done = true\na done\nin main, a.done=true, b.done=true
\nIf you have cyclic module dependencies in your program, make sure to\nplan accordingly.\n\n
\n" }, { "textRaw": "File Modules", "name": "File Modules", "type": "misc", "desc": "If the exact filename is not found, then Node.js will attempt to load the\nrequired filename with the added extensions: .js
, .json
, and finally\n.node
.\n\n
.js
files are interpreted as JavaScript text files, and .json
files are\nparsed as JSON text files. .node
files are interpreted as compiled addon\nmodules loaded with dlopen
.\n\n
A required module prefixed with '/'
is an absolute path to the file. For\nexample, require('/home/marco/foo.js')
will load the file at\n/home/marco/foo.js
.\n\n
A required module prefixed with './'
is relative to the file calling\nrequire()
. That is, circle.js
must be in the same directory as foo.js
for\nrequire('./circle')
to find it.\n\n
Without a leading '/', './', or '../' to indicate a file, the module must\neither be a core module or is loaded from a node_modules
folder.\n\n
If the given path does not exist, require()
will throw an [Error
][] with its\ncode
property set to 'MODULE_NOT_FOUND'
.\n\n
It is convenient to organize programs and libraries into self-contained\ndirectories, and then provide a single entry point to that library.\nThere are three ways in which a folder may be passed to require()
as\nan argument.\n\n
The first is to create a package.json
file in the root of the folder,\nwhich specifies a main
module. An example package.json file might\nlook like this:\n\n
{ "name" : "some-library",\n "main" : "./lib/some-library.js" }
\nIf this was in a folder at ./some-library
, then\nrequire('./some-library')
would attempt to load\n./some-library/lib/some-library.js
.\n\n
This is the extent of Node.js's awareness of package.json files.\n\n
\nNote: If the file specified by the "main"
entry of package.json
is missing\nand can not be resolved, Node.js will report the entire module as missing with\nthe default error:\n\n
Error: Cannot find module 'some-library'
\nIf there is no package.json file present in the directory, then Node.js\nwill attempt to load an index.js
or index.node
file out of that\ndirectory. For example, if there was no package.json file in the above\nexample, then require('./some-library')
would attempt to load:\n\n
./some-library/index.js
./some-library/index.node
If the module identifier passed to require()
is not a native module,\nand does not begin with '/'
, '../'
, or './'
, then Node.js starts at the\nparent directory of the current module, and adds /node_modules
, and\nattempts to load the module from that location. Node will not append\nnode_modules
to a path already ending in node_modules
.\n\n
If it is not found there, then it moves to the parent directory, and so\non, until the root of the file system is reached.\n\n
\nFor example, if the file at '/home/ry/projects/foo.js'
called\nrequire('bar.js')
, then Node.js would look in the following locations, in\nthis order:\n\n
/home/ry/projects/node_modules/bar.js
/home/ry/node_modules/bar.js
/home/node_modules/bar.js
/node_modules/bar.js
This allows programs to localize their dependencies, so that they do not\nclash.\n\n
\nYou can require specific files or sub modules distributed with a module by\nincluding a path suffix after the module name. For instance\nrequire('example-module/path/to/file')
would resolve path/to/file
\nrelative to where example-module
is located. The suffixed path follows the\nsame module resolution semantics.\n\n
If the NODE_PATH
environment variable is set to a colon-delimited list\nof absolute paths, then Node.js will search those paths for modules if they\nare not found elsewhere. (Note: On Windows, NODE_PATH
is delimited by\nsemicolons instead of colons.)\n\n
NODE_PATH
was originally created to support loading modules from\nvarying paths before the current [module resolution][] algorithm was frozen.\n\n
NODE_PATH
is still supported, but is less necessary now that the Node.js\necosystem has settled on a convention for locating dependent modules.\nSometimes deployments that rely on NODE_PATH
show surprising behavior\nwhen people are unaware that NODE_PATH
must be set. Sometimes a\nmodule's dependencies change, causing a different version (or even a\ndifferent module) to be loaded as the NODE_PATH
is searched.\n\n
Additionally, Node.js will search in the following locations:\n\n
\n$HOME/.node_modules
$HOME/.node_libraries
$PREFIX/lib/node
Where $HOME
is the user's home directory, and $PREFIX
is Node.js's\nconfigured node_prefix
.\n\n
These are mostly for historic reasons. You are highly encouraged\nto place your dependencies locally in node_modules
folders. They\nwill be loaded faster, and more reliably.\n\n
In each module, the module
free variable is a reference to the object\nrepresenting the current module. For convenience, module.exports
is\nalso accessible via the exports
module-global. module
isn't actually\na global but rather local to each module.\n\n
The module objects required by this one.\n\n
\n" }, { "textRaw": "`exports` {Object} ", "type": "Object", "name": "exports", "desc": "The module.exports
object is created by the Module system. Sometimes this is\nnot acceptable; many want their module to be an instance of some class. To do\nthis, assign the desired export object to module.exports
. Note that assigning\nthe desired object to exports
will simply rebind the local exports
variable,\nwhich is probably not what you want to do.\n\n
For example suppose we were making a module called a.js
\n\n
const EventEmitter = require('events');\n\nmodule.exports = new EventEmitter();\n\n// Do some work, and after some time emit\n// the 'ready' event from the module itself.\nsetTimeout(() => {\n module.exports.emit('ready');\n}, 1000);
\nThen in another file we could do\n\n
\nconst a = require('./a');\na.on('ready', () => {\n console.log('module a is ready');\n});
\nNote that assignment to module.exports
must be done immediately. It cannot be\ndone in any callbacks. This does not work:\n\n
x.js:\n\n
\nsetTimeout(() => {\n module.exports = { a: 'hello' };\n}, 0);
\ny.js:\n\n
\nconst x = require('./x');\nconsole.log(x.a);
\n",
"modules": [
{
"textRaw": "exports alias",
"name": "exports_alias",
"desc": "The exports
variable that is available within a module starts as a reference\nto module.exports
. As with any variable, if you assign a new value to it, it\nis no longer bound to the previous value.\n\n
To illustrate the behavior, imagine this hypothetical implementation of\nrequire()
:\n\n
function require(...) {\n // ...\n ((module, exports) => {\n // Your module code here\n exports = some_func; // re-assigns exports, exports is no longer\n // a shortcut, and nothing is exported.\n module.exports = some_func; // makes your module export 0\n })(module, module.exports);\n return module;\n}
\nAs a guideline, if the relationship between exports
and module.exports
\nseems like magic to you, ignore exports
and only use module.exports
.\n\n
The fully resolved filename to the module.\n\n
\n" }, { "textRaw": "`id` {String} ", "type": "String", "name": "id", "desc": "The identifier for the module. Typically this is the fully resolved\nfilename.\n\n
\n" }, { "textRaw": "`loaded` {Boolean} ", "type": "Boolean", "name": "loaded", "desc": "Whether or not the module is done loading, or is in the process of\nloading.\n\n
\n" }, { "textRaw": "`parent` {Object} Module object ", "type": "Object", "name": "parent", "desc": "The module that first required this one.\n\n
\n", "shortDesc": "Module object" } ], "methods": [ { "textRaw": "module.require(id)", "type": "method", "name": "require", "signatures": [ { "return": { "textRaw": "Return: {Object} `module.exports` from the resolved module ", "name": "return", "type": "Object", "desc": "`module.exports` from the resolved module" }, "params": [ { "textRaw": "`id` {String} ", "name": "id", "type": "String" } ] }, { "params": [ { "name": "id" } ] } ], "desc": "The module.require
method provides a way to load a module as if\nrequire()
was called from the original module.\n\n
Note that in order to do this, you must get a reference to the module
\nobject. Since require()
returns the module.exports
, and the module
is\ntypically only available within a specific module's code, it must be\nexplicitly exported in order to be used.\n\n
The net
module provides you with an asynchronous network wrapper. It contains\nfunctions for creating both servers and clients (called streams). You can include\nthis module with require('net');
.\n\n
This class is used to create a TCP or local server.\n\n
\nnet.Server
is an [EventEmitter
][] with the following events:\n\n
Emitted when the server closes. Note that if connections exist, this\nevent is not emitted until all connections are ended.\n\n
\n", "params": [] }, { "textRaw": "Event: 'connection'", "type": "event", "name": "connection", "params": [], "desc": "Emitted when a new connection is made. socket
is an instance of\nnet.Socket
.\n\n
Emitted when an error occurs. The ['close'
][] event will be called directly\nfollowing this event. See example in discussion of server.listen
.\n\n
Emitted when the server has been bound after calling server.listen
.\n\n
Returns the bound address, the address family name and port of the server\nas reported by the operating system.\nUseful to find which port was assigned when giving getting an OS-assigned address.\nReturns an object with three properties, e.g.\n{ port: 12346, family: 'IPv4', address: '127.0.0.1' }
\n\n
Example:\n\n
\nvar server = net.createServer((socket) => {\n socket.end('goodbye\\n');\n}).on('error', (err) => {\n // handle errors here\n throw err;\n});\n\n// grab a random port.\nserver.listen(() => {\n address = server.address();\n console.log('opened server on %j', address);\n});
\nDon't call server.address()
until the 'listening'
event has been emitted.\n\n
Stops the server from accepting new connections and keeps existing\nconnections. This function is asynchronous, the server is finally\nclosed when all connections are ended and the server emits a ['close'
][] event.\nThe optional callback
will be called once the 'close'
event occurs. Unlike\nthat event, it will be called with an Error as its only argument if the server\nwas not open when it was closed.\n\n
Asynchronously get the number of concurrent connections on the server. Works\nwhen sockets were sent to forks.\n\n
\nCallback should take two arguments err
and count
.\n\n
The handle
object can be set to either a server or socket (anything\nwith an underlying _handle
member), or a {fd: <n>}
object.\n\n
This will cause the server to accept connections on the specified\nhandle, but it is presumed that the file descriptor or handle has\nalready been bound to a port or domain socket.\n\n
\nListening on a file descriptor is not supported on Windows.\n\n
\nThis function is asynchronous. When the server has been bound,\n['listening'
][] event will be emitted.\nThe last parameter callback
will be added as a listener for the\n['listening'
][] event.\n\n
The parameter backlog
behaves the same as in\n[server.listen(port[, hostname][, backlog][, callback])
][server.listen(port, host, backlog, callback)
].\n\n
The port
, host
, and backlog
properties of options
, as well as the\noptional callback function, behave as they do on a call to\n[server.listen(port[, hostname][, backlog][, callback])
][server.listen(port, host, backlog, callback)
].\nAlternatively, the path
option can be used to specify a UNIX socket.\n\n
If exclusive
is false
(default), then cluster workers will use the same\nunderlying handle, allowing connection handling duties to be shared. When\nexclusive
is true
, the handle is not shared, and attempted port sharing\nresults in an error. An example which listens on an exclusive port is\nshown below.\n\n
server.listen({\n host: 'localhost',\n port: 80,\n exclusive: true\n});
\n"
},
{
"textRaw": "server.listen(path[, backlog][, callback])",
"type": "method",
"name": "listen",
"signatures": [
{
"params": [
{
"textRaw": "`path` {String} ",
"name": "path",
"type": "String"
},
{
"textRaw": "`backlog` {Number} ",
"name": "backlog",
"type": "Number",
"optional": true
},
{
"textRaw": "`callback` {Function} ",
"name": "callback",
"type": "Function",
"optional": true
}
]
},
{
"params": [
{
"name": "path"
},
{
"name": "backlog",
"optional": true
},
{
"name": "callback",
"optional": true
}
]
}
],
"desc": "Start a local socket server listening for connections on the given path
.\n\n
This function is asynchronous. When the server has been bound,\n['listening'
][] event will be emitted. The last parameter callback
\nwill be added as a listener for the ['listening'
][] event.\n\n
On UNIX, the local domain is usually known as the UNIX domain. The path is a\nfilesystem path name. It is subject to the same naming conventions and\npermissions checks as would be done on file creation, will be visible in the\nfilesystem, and will persist until unlinked.\n\n
\nOn Windows, the local domain is implemented using a named pipe. The path must\nrefer to an entry in \\\\?\\pipe\\
or \\\\.\\pipe\\
. Any characters are permitted,\nbut the latter may do some processing of pipe names, such as resolving ..
\nsequences. Despite appearances, the pipe name space is flat. Pipes will not\npersist, they are removed when the last reference to them is closed. Do not\nforget JavaScript string escaping requires paths to be specified with\ndouble-backslashes, such as:\n\n
net.createServer().listen(\n path.join('\\\\\\\\?\\\\pipe', process.cwd(), 'myctl'))
\nThe parameter backlog
behaves the same as in\n[server.listen(port[, hostname][, backlog][, callback])
][server.listen(port, host, backlog, callback)
].\n\n
Begin accepting connections on the specified port
and hostname
. If the\nhostname
is omitted, the server will accept connections on any IPv6 address\n(::
) when IPv6 is available, or any IPv4 address (0.0.0.0
) otherwise. A\nport value of zero will assign a random port.\n\n
Backlog is the maximum length of the queue of pending connections.\nThe actual length will be determined by your OS through sysctl settings such as\ntcp_max_syn_backlog
and somaxconn
on linux. The default value of this\nparameter is 511 (not 512).\n\n
This function is asynchronous. When the server has been bound,\n['listening'
][] event will be emitted. The last parameter callback
\nwill be added as a listener for the ['listening'
][] event.\n\n
One issue some users run into is getting EADDRINUSE
errors. This means that\nanother server is already running on the requested port. One way of handling this\nwould be to wait a second and then try again. This can be done with\n\n
server.on('error', (e) => {\n if (e.code == 'EADDRINUSE') {\n console.log('Address in use, retrying...');\n setTimeout(() => {\n server.close();\n server.listen(PORT, HOST);\n }, 1000);\n }\n});
\n(Note: All sockets in Node.js set SO_REUSEADDR
already)\n\n
Opposite of unref
, calling ref
on a previously unref
d server will not\nlet the program exit if it's the only server left (the default behavior). If\nthe server is ref
d calling ref
again will have no effect.\n\n
Returns server
.\n\n
Calling unref
on a server will allow the program to exit if this is the only\nactive server in the event system. If the server is already unref
d calling\nunref
again will have no effect.\n\n
Returns server
.\n\n
The number of concurrent connections on the server.\n\n
\nThis becomes null
when sending a socket to a child with\n[child_process.fork()
][]. To poll forks and get current number of active\nconnections use asynchronous server.getConnections
instead.\n\n
A Boolean indicating whether or not the server is listening for\nconnections.\n\n
\n" }, { "textRaw": "server.maxConnections", "name": "maxConnections", "desc": "Set this property to reject connections when the server's connection count gets\nhigh.\n\n
\nIt is not recommended to use this option once a socket has been sent to a child\nwith [child_process.fork()
][].\n\n
This object is an abstraction of a TCP or local socket. net.Socket
\ninstances implement a duplex Stream interface. They can be created by the\nuser and used as a client (with [connect()
][]) or they can be created by Node.js\nand passed to the user through the 'connection'
event of a server.\n\n
Construct a new socket object.\n\n
\noptions
is an object with the following defaults:\n\n
{\n fd: null,\n allowHalfOpen: false,\n readable: false,\n writable: false\n}
\nfd
allows you to specify the existing file descriptor of socket.\nSet readable
and/or writable
to true
to allow reads and/or writes on this\nsocket (NOTE: Works only when fd
is passed).\nAbout allowHalfOpen
, refer to createServer()
and 'end'
event.\n\n
net.Socket
instances are [EventEmitter
][] with the following events:\n\n
Returns the bound address, the address family name and port of the\nsocket as reported by the operating system. Returns an object with\nthree properties, e.g.\n{ port: 12346, family: 'IPv4', address: '127.0.0.1' }
\n\n
Opens the connection for a given socket.\n\n
\nFor TCP sockets, options
argument should be an object which specifies:\n\n
port
: Port the client should connect to (Required).
host
: Host the client should connect to. Defaults to 'localhost'
.
localAddress
: Local interface to bind to for network connections.
localPort
: Local port to bind to for network connections.
family
: Version of IP stack. Defaults to 4
.
hints
: [dns.lookup()
hints][]. Defaults to 0
.
lookup
: Custom lookup function. Defaults to dns.lookup
.
For local domain sockets, options
argument should be an object which\nspecifies:\n\n
path
: Path the client should connect to (Required).Normally this method is not needed, as net.createConnection
opens the\nsocket. Use this only if you are implementing a custom Socket.\n\n
This function is asynchronous. When the ['connect'
][] event is emitted the\nsocket is established. If there is a problem connecting, the 'connect'
event\nwill not be emitted, the ['error'
][] event will be emitted with the exception.\n\n
The connectListener
parameter will be added as a listener for the\n['connect'
][] event.\n\n
As [socket.connect(options\\[, connectListener\\])
][socket.connect(options, connectListener)
],\nwith options either as either {port: port, host: host}
or {path: path}
.\n\n
As [socket.connect(options\\[, connectListener\\])
][socket.connect(options, connectListener)
],\nwith options either as either {port: port, host: host}
or {path: path}
.\n\n
Ensures that no more I/O activity happens on this socket. Only necessary in\ncase of errors (parse error or so).\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "socket.end([data][, encoding])", "type": "method", "name": "end", "desc": "Half-closes the socket. i.e., it sends a FIN packet. It is possible the\nserver will still send some data.\n\n
\nIf data
is specified, it is equivalent to calling\nsocket.write(data, encoding)
followed by socket.end()
.\n\n
Pauses the reading of data. That is, ['data'
][] events will not be emitted.\nUseful to throttle back an upload.\n\n
Opposite of unref
, calling ref
on a previously unref
d socket will not\nlet the program exit if it's the only socket left (the default behavior). If\nthe socket is ref
d calling ref
again will have no effect.\n\n
Returns socket
.\n\n
Resumes reading after a call to [pause()
][].\n\n
Set the encoding for the socket as a [Readable Stream][]. See\n[stream.setEncoding()
][] for more information.\n\n
Enable/disable keep-alive functionality, and optionally set the initial\ndelay before the first keepalive probe is sent on an idle socket.\nenable
defaults to false
.\n\n
Set initialDelay
(in milliseconds) to set the delay between the last\ndata packet received and the first keepalive probe. Setting 0 for\ninitialDelay will leave the value unchanged from the default\n(or previous) setting. Defaults to 0
.\n\n
Returns socket
.\n\n
Disables the Nagle algorithm. By default TCP connections use the Nagle\nalgorithm, they buffer data before sending it off. Setting true
for\nnoDelay
will immediately fire off data each time socket.write()
is called.\nnoDelay
defaults to true
.\n\n
Returns socket
.\n\n
Sets the socket to timeout after timeout
milliseconds of inactivity on\nthe socket. By default net.Socket
do not have a timeout.\n\n
When an idle timeout is triggered the socket will receive a ['timeout'
][]\nevent but the connection will not be severed. The user must manually [end()
][]\nor [destroy()
][] the socket.\n\n
If timeout
is 0, then the existing idle timeout is disabled.\n\n
The optional callback
parameter will be added as a one time listener for the\n['timeout'
][] event.\n\n
Returns socket
.\n\n
Calling unref
on a socket will allow the program to exit if this is the only\nactive socket in the event system. If the socket is already unref
d calling\nunref
again will have no effect.\n\n
Returns socket
.\n\n
Sends data on the socket. The second parameter specifies the encoding in the\ncase of a string--it defaults to UTF8 encoding.\n\n
\nReturns true
if the entire data was flushed successfully to the kernel\nbuffer. Returns false
if all or part of the data was queued in user memory.\n['drain'
][] will be emitted when the buffer is again free.\n\n
The optional callback
parameter will be executed when the data is finally\nwritten out - this may not be immediately.\n\n
Emitted once the socket is fully closed. The argument had_error
is a boolean\nwhich says if the socket was closed due to a transmission error.\n\n
Emitted when a socket connection is successfully established.\nSee [connect()
][].\n\n
Emitted when data is received. The argument data
will be a Buffer
or\nString
. Encoding of data is set by socket.setEncoding()
.\n(See the [Readable Stream][] section for more information.)\n\n
Note that the data will be lost if there is no listener when a Socket
\nemits a 'data'
event.\n\n
Emitted when the write buffer becomes empty. Can be used to throttle uploads.\n\n
\nSee also: the return values of socket.write()
\n\n
Emitted when the other end of the socket sends a FIN packet.\n\n
\nBy default (allowHalfOpen == false
) the socket will destroy its file\ndescriptor once it has written out its pending write queue. However, by\nsetting allowHalfOpen == true
the socket will not automatically end()
\nits side allowing the user to write arbitrary amounts of data, with the\ncaveat that the user is required to end()
their side now.\n\n
Emitted when an error occurs. The 'close'
event will be called directly\nfollowing this event.\n\n
Emitted after resolving the hostname but before connecting.\nNot applicable to UNIX sockets.\n\n
\nerr
{Error|Null} The error object. See [dns.lookup()
][].address
{String} The IP address.family
{String|Null} The address type. See [dns.lookup()
][].host
{String} The hostname.Emitted if the socket times out from inactivity. This is only to notify that\nthe socket has been idle. The user must manually close the connection.\n\n
\nSee also: [socket.setTimeout()
][]\n\n
net.Socket
has the property that socket.write()
always works. This is to\nhelp users get up and running quickly. The computer cannot always keep up\nwith the amount of data that is written to a socket - the network connection\nsimply might be too slow. Node.js will internally queue up the data written to a\nsocket and send it out over the wire when it is possible. (Internally it is\npolling on the socket's file descriptor for being writable).\n\n
The consequence of this internal buffering is that memory may grow. This\nproperty shows the number of characters currently buffered to be written.\n(Number of characters is approximately equal to the number of bytes to be\nwritten, but the buffer may contain strings, and the strings are lazily\nencoded, so the exact number of bytes is not known.)\n\n
\nUsers who experience large or growing bufferSize
should attempt to\n"throttle" the data flows in their program with [pause()
][] and [resume()
][].\n\n
The amount of received bytes.\n\n
\n" }, { "textRaw": "socket.bytesWritten", "name": "bytesWritten", "desc": "The amount of bytes sent.\n\n
\n" }, { "textRaw": "socket.connecting", "name": "connecting", "desc": "If true
- [socket.connect(options\\[, connectListener\\])
][] was called and\nhaven't yet finished. Will be set to false
before emitting connect
event\nand/or calling [socket.connect(options\\[, connectListener\\])
][]'s callback.\n\n
The string representation of the local IP address the remote client is\nconnecting on. For example, if you are listening on '0.0.0.0'
and the\nclient connects on '192.168.1.1'
, the value would be '192.168.1.1'
.\n\n
The numeric representation of the local port. For example,\n80
or 21
.\n\n
The string representation of the remote IP address. For example,\n'74.125.127.100'
or '2001:4860:a005::68'
. Value may be undefined
if\nthe socket is destroyed (for example, if the client disconnected).\n\n
The string representation of the remote IP family. 'IPv4'
or 'IPv6'
.\n\n
The numeric representation of the remote port. For example,\n80
or 21
.\n\n
A factory function, which returns a new [net.Socket
][] and automatically\nconnects with the supplied options
.\n\n
The options are passed to both the [net.Socket
][] constructor and the\n[socket.connect
][] method.\n\n
The connectListener
parameter will be added as a listener for the\n['connect'
][] event once.\n\n
Here is an example of a client of the previously described echo server:\n\n
\nconst net = require('net');\nconst client = net.connect({port: 8124}, () => {\n // 'connect' listener\n console.log('connected to server!');\n client.write('world!\\r\\n');\n});\nclient.on('data', (data) => {\n console.log(data.toString());\n client.end();\n});\nclient.on('end', () => {\n console.log('disconnected from server');\n});
\nTo connect on the socket /tmp/echo.sock
the second line would just be\nchanged to\n\n
const client = net.connect({path: '/tmp/echo.sock'});
\n",
"signatures": [
{
"params": [
{
"name": "options"
},
{
"name": "connectListener",
"optional": true
}
]
}
]
},
{
"textRaw": "net.connect(path[, connectListener])",
"type": "method",
"name": "connect",
"desc": "A factory function, which returns a new unix [net.Socket
][] and automatically\nconnects to the supplied path
.\n\n
The connectListener
parameter will be added as a listener for the\n['connect'
][] event once.\n\n
A factory function, which returns a new [net.Socket
][] and automatically\nconnects to the supplied port
and host
.\n\n
If host
is omitted, 'localhost'
will be assumed.\n\n
The connectListener
parameter will be added as a listener for the\n['connect'
][] event once.\n\n
A factory function, which returns a new [net.Socket
][] and automatically\nconnects with the supplied options
.\n\n
The options are passed to both the [net.Socket
][] constructor and the\n[socket.connect
][] method.\n\n
The connectListener
parameter will be added as a listener for the\n['connect'
][] event once.\n\n
Here is an example of a client of the previously described echo server:\n\n
\nconst net = require('net');\nconst client = net.createConnection({port: 8124}, () => {\n //'connect' listener\n console.log('connected to server!');\n client.write('world!\\r\\n');\n});\nclient.on('data', (data) => {\n console.log(data.toString());\n client.end();\n});\nclient.on('end', () => {\n console.log('disconnected from server');\n});
\nTo connect on the socket /tmp/echo.sock
the second line would just be\nchanged to\n\n
const client = net.connect({path: '/tmp/echo.sock'});
\n",
"signatures": [
{
"params": [
{
"name": "options"
},
{
"name": "connectListener",
"optional": true
}
]
}
]
},
{
"textRaw": "net.createConnection(path[, connectListener])",
"type": "method",
"name": "createConnection",
"desc": "A factory function, which returns a new unix [net.Socket
][] and automatically\nconnects to the supplied path
.\n\n
The connectListener
parameter will be added as a listener for the\n['connect'
][] event once.\n\n
A factory function, which returns a new [net.Socket
][] and automatically\nconnects to the supplied port
and host
.\n\n
If host
is omitted, 'localhost'
will be assumed.\n\n
The connectListener
parameter will be added as a listener for the\n['connect'
][] event once.\n\n
Creates a new server. The connectionListener
argument is\nautomatically set as a listener for the ['connection'
][] event.\n\n
options
is an object with the following defaults:\n\n
{\n allowHalfOpen: false,\n pauseOnConnect: false\n}
\nIf allowHalfOpen
is true
, then the socket won't automatically send a FIN\npacket when the other end of the socket sends a FIN packet. The socket becomes\nnon-readable, but still writable. You should call the [end()
][] method explicitly.\nSee ['end'
][] event for more information.\n\n
If pauseOnConnect
is true
, then the socket associated with each incoming\nconnection will be paused, and no data will be read from its handle. This allows\nconnections to be passed between processes without any data being read by the\noriginal process. To begin reading data from a paused socket, call [resume()
][].\n\n
Here is an example of an echo server which listens for connections\non port 8124:\n\n
\nconst net = require('net');\nconst server = net.createServer((c) => {\n // 'connection' listener\n console.log('client connected');\n c.on('end', () => {\n console.log('client disconnected');\n });\n c.write('hello\\r\\n');\n c.pipe(c);\n});\nserver.on('error', (err) => {\n throw err;\n});\nserver.listen(8124, () => {\n console.log('server bound');\n});
\nTest this by using telnet
:\n\n
telnet localhost 8124
\nTo listen on the socket /tmp/echo.sock
the third line from the last would\njust be changed to\n\n
server.listen('/tmp/echo.sock', () => {\n console.log('server bound');\n});
\nUse nc
to connect to a UNIX domain socket server:\n\n
nc -U /tmp/echo.sock
\n",
"signatures": [
{
"params": [
{
"name": "options",
"optional": true
},
{
"name": "connectionListener",
"optional": true
}
]
}
]
},
{
"textRaw": "net.isIP(input)",
"type": "method",
"name": "isIP",
"desc": "Tests if input is an IP address. Returns 0 for invalid strings,\nreturns 4 for IP version 4 addresses, and returns 6 for IP version 6 addresses.\n\n\n
\n", "signatures": [ { "params": [ { "name": "input" } ] } ] }, { "textRaw": "net.isIPv4(input)", "type": "method", "name": "isIPv4", "desc": "Returns true if input is a version 4 IP address, otherwise returns false.\n\n\n
\n", "signatures": [ { "params": [ { "name": "input" } ] } ] }, { "textRaw": "net.isIPv6(input)", "type": "method", "name": "isIPv6", "desc": "Returns true if input is a version 6 IP address, otherwise returns false.\n\n
\n", "signatures": [ { "params": [ { "name": "input" } ] } ] } ], "type": "module", "displayName": "net" }, { "textRaw": "OS", "name": "os", "stability": 2, "stabilityText": "Stable", "desc": "Provides a few basic operating-system related utility functions.\n\n
\nUse require('os')
to access this module.\n\n
A constant defining the appropriate End-of-line marker for the operating\nsystem.\n\n
\n" } ], "methods": [ { "textRaw": "os.arch()", "type": "method", "name": "arch", "desc": "Returns the operating system CPU architecture. Possible values are 'x64'
,\n'arm'
and 'ia32'
. Returns the value of [process.arch
][].\n\n
Returns an array of objects containing information about each CPU/core\ninstalled: model, speed (in MHz), and times (an object containing the number of\nmilliseconds the CPU/core spent in: user, nice, sys, idle, and irq).\n\n
\nExample inspection of os.cpus:\n\n
\n[ { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times:\n { user: 252020,\n nice: 0,\n sys: 30340,\n idle: 1070356870,\n irq: 0 } },\n { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times:\n { user: 306960,\n nice: 0,\n sys: 26980,\n idle: 1071569080,\n irq: 0 } },\n { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times:\n { user: 248450,\n nice: 0,\n sys: 21750,\n idle: 1070919370,\n irq: 0 } },\n { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times:\n { user: 256880,\n nice: 0,\n sys: 19430,\n idle: 1070905480,\n irq: 20 } },\n { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times:\n { user: 511580,\n nice: 20,\n sys: 40900,\n idle: 1070842510,\n irq: 0 } },\n { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times:\n { user: 291660,\n nice: 0,\n sys: 34360,\n idle: 1070888000,\n irq: 10 } },\n { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times:\n { user: 308260,\n nice: 0,\n sys: 55410,\n idle: 1071129970,\n irq: 880 } },\n { model: 'Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz',\n speed: 2926,\n times:\n { user: 266450,\n nice: 1480,\n sys: 34920,\n idle: 1072572010,\n irq: 30 } } ]
\nNote that since nice
values are UNIX centric in Windows the nice
values of\nall processors are always 0.\n\n
Returns the endianness of the CPU. Possible values are 'BE'
for big endian\nor 'LE'
for little endian.\n\n
Returns the amount of free system memory in bytes.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "os.homedir()", "type": "method", "name": "homedir", "desc": "Returns the home directory of the current user.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "os.hostname()", "type": "method", "name": "hostname", "desc": "Returns the hostname of the operating system.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "os.loadavg()", "type": "method", "name": "loadavg", "desc": "Returns an array containing the 1, 5, and 15 minute load averages.\n\n
\nThe load average is a measure of system activity, calculated by the operating\nsystem and expressed as a fractional number. As a rule of thumb, the load\naverage should ideally be less than the number of logical CPUs in the system.\n\n
\nThe load average is a very UNIX-y concept; there is no real equivalent on\nWindows platforms. That is why this function always returns [0, 0, 0]
on\nWindows.\n\n
Get a list of network interfaces:\n\n
\n{ lo:\n [ { address: '127.0.0.1',\n netmask: '255.0.0.0',\n family: 'IPv4',\n mac: '00:00:00:00:00:00',\n internal: true },\n { address: '::1',\n netmask: 'ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff',\n family: 'IPv6',\n mac: '00:00:00:00:00:00',\n internal: true } ],\n eth0:\n [ { address: '192.168.1.108',\n netmask: '255.255.255.0',\n family: 'IPv4',\n mac: '01:02:03:0a:0b:0c',\n internal: false },\n { address: 'fe80::a00:27ff:fe4e:66a1',\n netmask: 'ffff:ffff:ffff:ffff::',\n family: 'IPv6',\n mac: '01:02:03:0a:0b:0c',\n internal: false } ] }
\nNote that due to the underlying implementation this will only return network\ninterfaces that have been assigned an address.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "os.platform()", "type": "method", "name": "platform", "desc": "Returns the operating system platform. Possible values are 'darwin'
,\n'freebsd'
, 'linux'
, 'sunos'
or 'win32'
. Returns the value of\n[process.platform
][].\n\n
Returns the operating system release.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "os.tmpdir()", "type": "method", "name": "tmpdir", "desc": "Returns the operating system's default directory for temporary files.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "os.totalmem()", "type": "method", "name": "totalmem", "desc": "Returns the total amount of system memory in bytes.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "os.type()", "type": "method", "name": "type", "desc": "Returns the operating system name. For example 'Linux'
on Linux, 'Darwin'
\non OS X and 'Windows_NT'
on Windows.\n\n
Returns the system uptime in seconds.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "os.userInfo([options])", "type": "method", "name": "userInfo", "signatures": [ { "params": [ { "textRaw": "`options` {Object} ", "options": [ { "textRaw": "`encoding` {String} Character encoding used to interpret resulting strings. If `encoding` is set to `'buffer'`, the `username`, `shell`, and `homedir` values will be `Buffer` instances. (Default: 'utf8') ", "name": "encoding", "default": "utf8", "type": "String", "desc": "Character encoding used to interpret resulting strings. If `encoding` is set to `'buffer'`, the `username`, `shell`, and `homedir` values will be `Buffer` instances." } ], "name": "options", "type": "Object", "optional": true } ] }, { "params": [ { "name": "options", "optional": true } ] } ], "desc": "Returns a subset of the password file entry for the current effective user. The\nreturned object includes the username
, uid
, gid
, shell
, and homedir
.\nOn Windows, the uid
and gid
fields are -1
, and shell
is null
.\n\n
The value of homedir
returned by userInfo()
comes directly from the\noperating system. This differs from the result of os.homedir()
, which queries\nseveral environment variables for the home directory before falling back to the\noperating system response.\n\n
This module contains utilities for handling and transforming file\npaths. The file system is not consulted to check whether paths are valid.\n\n
\nUse require('path')
to use this module. The following methods are provided:\n\n
Return the last portion of a path, similar to the Unix basename
command.\npath
must be a string. ext
, if given, must also be a string.\n\n
Examples:\n\n
\npath.basename('/foo/bar/baz/asdf/quux.html')\n// returns 'quux.html'\n\npath.basename('/foo/bar/baz/asdf/quux.html', '.html')\n// returns 'quux'
\n",
"signatures": [
{
"params": [
{
"name": "path"
},
{
"name": "ext",
"optional": true
}
]
}
]
},
{
"textRaw": "path.dirname(path)",
"type": "method",
"name": "dirname",
"desc": "Return the directory name of a path, similar to the Unix dirname
command.\npath
must be a string.\n\n
Example:\n\n
\npath.dirname('/foo/bar/baz/asdf/quux')\n// returns '/foo/bar/baz/asdf'
\n",
"signatures": [
{
"params": [
{
"name": "path"
}
]
}
]
},
{
"textRaw": "path.extname(path)",
"type": "method",
"name": "extname",
"desc": "Return the extension of the path, from the last '.' to end of string\nin the last portion of the path. If there is no '.' in the last portion\nof the path or the first character of it is '.', then it returns\nan empty string. path
must be a string.\n\n
Examples:\n\n
\npath.extname('index.html')\n// returns '.html'\n\npath.extname('index.coffee.md')\n// returns '.md'\n\npath.extname('index.')\n// returns '.'\n\npath.extname('index')\n// returns ''\n\npath.extname('.index')\n// returns ''
\n",
"signatures": [
{
"params": [
{
"name": "path"
}
]
}
]
},
{
"textRaw": "path.format(pathObject)",
"type": "method",
"name": "format",
"desc": "Returns a path string from an object. This is the opposite of [path.parse
][].\n\n
If pathObject
has dir
and base
properties, the returned string will\nbe a concatenation of the dir
property, the platform-dependent path separator,\nand the base
property.\n\n
If the dir
property is not supplied, the root
property will be used as the\ndir
property. However, it will be assumed that the root
property already\nends with the platform-dependent path separator. In this case, the returned\nstring will be the concatenation of the root
property and the base
property.\n\n
If both the dir
and the root
properties are not supplied, then the returned\nstring will be the contents of the base
property.\n\n
If the base
property is not supplied, a concatenation of the name
property\nand the ext
property will be used as the base
property.\n\n
Examples:\n\n
\nSome Posix system examples:\n\n
\n// If `dir` and `base` are provided, `dir` + platform separator + `base`\n// will be returned.\npath.format({\n dir: '/home/user/dir',\n base: 'file.txt'\n});\n// returns '/home/user/dir/file.txt'\n\n// `root` will be used if `dir` is not specified.\n// `name` + `ext` will be used if `base` is not specified.\n// If only `root` is provided or `dir` is equal to `root` then the\n// platform separator will not be included.\npath.format({\n root: '/',\n base: 'file.txt'\n});\n// returns '/file.txt'\n\npath.format({\n dir: '/',\n root: '/',\n name: 'file',\n ext: '.txt'\n});\n// returns '/file.txt'\n\n// `base` will be returned if `dir` or `root` are not provided.\npath.format({\n base: 'file.txt'\n});\n// returns 'file.txt'
\nAn example on Windows:\n\n
\npath.format({\n root : "C:\\\\",\n dir : "C:\\\\path\\\\dir",\n base : "file.txt",\n ext : ".txt",\n name : "file"\n})\n// returns 'C:\\\\path\\\\dir\\\\file.txt'
\n",
"signatures": [
{
"params": [
{
"name": "pathObject"
}
]
}
]
},
{
"textRaw": "path.isAbsolute(path)",
"type": "method",
"name": "isAbsolute",
"desc": "Determines whether path
is an absolute path. An absolute path will always\nresolve to the same location, regardless of the working directory. path
must\nbe a string.\n\n
Examples on *nix:\n\n
\npath.isAbsolute('/foo/bar') // true\npath.isAbsolute('/baz/..') // true\npath.isAbsolute('qux/') // false\npath.isAbsolute('.') // false
\nExamples on Windows:\n\n
\npath.isAbsolute('//server') // true\npath.isAbsolute('C:/foo/..') // true\npath.isAbsolute('bar\\\\baz') // false\npath.isAbsolute('.') // false
\nNote: If the path string passed as parameter is a zero-length string, unlike\n other path module functions, it will be used as-is and false
will be\n returned.\n\n
Join all arguments together and normalize the resulting path.\n\n
\nAll arguments must be strings. In v0.8, non-string arguments were\nsilently ignored. In v0.10 and up, an exception is thrown.\n\n
\nExamples:\n\n
\npath.join('/foo', 'bar', 'baz/asdf', 'quux', '..')\n// returns '/foo/bar/baz/asdf'\n\npath.join('foo', {}, 'bar')\n// throws exception\nTypeError: Arguments to path.join must be strings
\nNote: If the arguments to join
have zero-length strings, unlike other path\n module functions, they will be ignored. If the joined path string is a\n zero-length string then '.'
will be returned, which represents the\n current working directory.\n\n
Normalize a path, taking care of '..'
and '.'
parts. path
must be a\nstring.\n\n
When multiple slashes are found, they're replaced by a single one;\nwhen the path contains a trailing slash, it is preserved.\nOn Windows backslashes are used.\n\n
\nExample:\n\n
\npath.normalize('/foo/bar//baz/asdf/quux/..')\n// returns '/foo/bar/baz/asdf'
\nNote: If the path string passed as argument is a zero-length string then '.'
\n will be returned, which represents the current working directory.\n\n
Returns an object from a path. path
must be a string.\n\n
An example on *nix:\n\n
\npath.parse('/home/user/dir/file.txt')\n// returns\n// {\n// root : "/",\n// dir : "/home/user/dir",\n// base : "file.txt",\n// ext : ".txt",\n// name : "file"\n// }
\nAn example on Windows:\n\n
\npath.parse('C:\\\\path\\\\dir\\\\index.html')\n// returns\n// {\n// root : "C:\\\\",\n// dir : "C:\\\\path\\\\dir",\n// base : "index.html",\n// ext : ".html",\n// name : "index"\n// }
\n",
"signatures": [
{
"params": [
{
"name": "path"
}
]
}
]
},
{
"textRaw": "path.relative(from, to)",
"type": "method",
"name": "relative",
"desc": "Solve the relative path from from
to to
. from
and to
must be strings.\n\n
At times we have two absolute paths, and we need to derive the relative\npath from one to the other. This is actually the reverse transform of\npath.resolve
, which means we see that:\n\n
path.resolve(from, path.relative(from, to)) == path.resolve(to)
\nExamples:\n\n
\npath.relative('C:\\\\orandea\\\\test\\\\aaa', 'C:\\\\orandea\\\\impl\\\\bbb')\n// returns '..\\\\..\\\\impl\\\\bbb'\n\npath.relative('/data/orandea/test/aaa', '/data/orandea/impl/bbb')\n// returns '../../impl/bbb'
\nNote: If the arguments to relative
have zero-length strings then the current\n working directory will be used instead of the zero-length strings. If\n both the paths are the same then a zero-length string will be returned.\n\n
Resolves to
to an absolute path. All arguments must be strings.\n\n
If to
isn't already absolute from
arguments are prepended in right to left\norder, until an absolute path is found. If after using all from
paths still\nno absolute path is found, the current working directory is used as well. The\nresulting path is normalized, and trailing slashes are removed unless the path\ngets resolved to the root directory. Empty string from
arguments are\nignored.\n\n
Another way to think of it is as a sequence of cd
commands in a shell.\n\n
path.resolve('foo/bar', '/tmp/file/', '..', 'a/../subfile')
\nIs similar to:\n\n
\ncd foo/bar\ncd /tmp/file/\ncd ..\ncd a/../subfile\npwd
\nThe difference is that the different paths don't need to exist and may also be\nfiles.\n\n
\nExamples:\n\n
\npath.resolve('/foo/bar', './baz')\n// returns '/foo/bar/baz'\n\npath.resolve('/foo/bar', '/tmp/file/')\n// returns '/tmp/file'\n\npath.resolve('wwwroot', 'static_files/png/', '../gif/image.gif')\n// if currently in /home/myself/node, it returns\n// '/home/myself/node/wwwroot/static_files/gif/image.gif'
\n",
"signatures": [
{
"params": [
{
"name": "from ...",
"optional": true
},
{
"name": "to"
}
]
}
]
}
],
"properties": [
{
"textRaw": "path.delimiter",
"name": "delimiter",
"desc": "The platform-specific path delimiter, ;
or ':'
.\n\n
An example on *nix:\n\n
\nconsole.log(process.env.PATH)\n// '/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin'\n\nprocess.env.PATH.split(path.delimiter)\n// returns ['/usr/bin', '/bin', '/usr/sbin', '/sbin', '/usr/local/bin']
\nAn example on Windows:\n\n
\nconsole.log(process.env.PATH)\n// 'C:\\Windows\\system32;C:\\Windows;C:\\Program Files\\node\\'\n\nprocess.env.PATH.split(path.delimiter)\n// returns ['C:\\\\Windows\\\\system32', 'C:\\\\Windows', 'C:\\\\Program Files\\\\node\\\\']
\n"
},
{
"textRaw": "path.posix",
"name": "posix",
"desc": "Provide access to aforementioned path
methods but always interact in a posix\ncompatible way.\n\n
The platform-specific file separator. '\\\\'
or '/'
.\n\n
An example on *nix:\n\n
\n'foo/bar/baz'.split(path.sep)\n// returns ['foo', 'bar', 'baz']
\nAn example on Windows:\n\n
\n'foo\\\\bar\\\\baz'.split(path.sep)\n// returns ['foo', 'bar', 'baz']
\n"
},
{
"textRaw": "path.win32",
"name": "win32",
"desc": "Provide access to aforementioned path
methods but always interact in a win32\ncompatible way.\n\n
[Punycode.js][] is bundled with Node.js v0.6.2+. Use require('punycode')
to\naccess it. (To use it with other Node.js versions, use npm to install the\npunycode
module first.)\n\n
Converts a Punycode string of ASCII-only symbols to a string of Unicode symbols.\n\n
\n// decode domain name parts\npunycode.decode('maana-pta'); // 'mañana'\npunycode.decode('--dqo34k'); // '☃-⌘'
\n",
"signatures": [
{
"params": [
{
"name": "string"
}
]
}
]
},
{
"textRaw": "punycode.encode(string)",
"type": "method",
"name": "encode",
"desc": "Converts a string of Unicode symbols to a Punycode string of ASCII-only symbols.\n\n
\n// encode domain name parts\npunycode.encode('mañana'); // 'maana-pta'\npunycode.encode('☃-⌘'); // '--dqo34k'
\n",
"signatures": [
{
"params": [
{
"name": "string"
}
]
}
]
},
{
"textRaw": "punycode.toASCII(domain)",
"type": "method",
"name": "toASCII",
"desc": "Converts a Unicode string representing a domain name to Punycode. Only the\nnon-ASCII parts of the domain name will be converted, i.e. it doesn't matter if\nyou call it with a domain that's already in ASCII.\n\n
\n// encode domain names\npunycode.toASCII('mañana.com'); // 'xn--maana-pta.com'\npunycode.toASCII('☃-⌘.com'); // 'xn----dqo34k.com'
\n",
"signatures": [
{
"params": [
{
"name": "domain"
}
]
}
]
},
{
"textRaw": "punycode.toUnicode(domain)",
"type": "method",
"name": "toUnicode",
"desc": "Converts a Punycode string representing a domain name to Unicode. Only the\nPunycoded parts of the domain name will be converted, i.e. it doesn't matter if\nyou call it on a string that has already been converted to Unicode.\n\n
\n// decode domain names\npunycode.toUnicode('xn--maana-pta.com'); // 'mañana.com'\npunycode.toUnicode('xn----dqo34k.com'); // '☃-⌘.com'
\n",
"signatures": [
{
"params": [
{
"name": "domain"
}
]
}
]
}
],
"properties": [
{
"textRaw": "punycode.ucs2",
"name": "ucs2",
"modules": [
{
"textRaw": "punycode.ucs2.decode(string)",
"name": "punycode.ucs2.decode(string)",
"desc": "Creates an array containing the numeric code point values of each Unicode\nsymbol in the string. While [JavaScript uses UCS-2 internally][], this function\nwill convert a pair of surrogate halves (each of which UCS-2 exposes as\nseparate characters) into a single code point, matching UTF-16.\n\n
\npunycode.ucs2.decode('abc'); // [0x61, 0x62, 0x63]\n// surrogate pair for U+1D306 tetragram for centre:\npunycode.ucs2.decode('\\uD834\\uDF06'); // [0x1D306]
\n",
"type": "module",
"displayName": "punycode.ucs2.decode(string)"
},
{
"textRaw": "punycode.ucs2.encode(codePoints)",
"name": "punycode.ucs2.encode(codepoints)",
"desc": "Creates a string based on an array of numeric code point values.\n\n
\npunycode.ucs2.encode([0x61, 0x62, 0x63]); // 'abc'\npunycode.ucs2.encode([0x1D306]); // '\\uD834\\uDF06'
\n",
"type": "module",
"displayName": "punycode.ucs2.encode(codePoints)"
}
]
},
{
"textRaw": "punycode.version",
"name": "version",
"desc": "A string representing the current Punycode.js version number.\n\n
\n" } ], "type": "module", "displayName": "punycode" }, { "textRaw": "Query String", "name": "querystring", "stability": 2, "stabilityText": "Stable", "desc": "This module provides utilities for dealing with query strings.\nIt provides the following methods:\n\n
\n", "properties": [ { "textRaw": "querystring.escape", "name": "escape", "desc": "The escape function used by querystring.stringify
,\nprovided so that it could be overridden if necessary.\n\n
The unescape function used by querystring.parse
,\nprovided so that it could be overridden if necessary.\n\n
It will try to use decodeURIComponent
in the first place,\nbut if that fails it falls back to a safer equivalent that\ndoesn't throw on malformed URLs.\n\n
Deserialize a query string to an object.\nOptionally override the default separator ('&'
) and assignment ('='
)\ncharacters.\n\n
Options object may contain maxKeys
property (equal to 1000 by default), it'll\nbe used to limit processed keys. Set it to 0 to remove key count limitation.\n\n
Options object may contain decodeURIComponent
property (querystring.unescape
by default),\nit can be used to decode a non-utf8
encoding string if necessary.\n\n
Example:\n\n
\nquerystring.parse('foo=bar&baz=qux&baz=quux&corge')\n// returns { foo: 'bar', baz: ['qux', 'quux'], corge: '' }\n\n// Suppose gbkDecodeURIComponent function already exists,\n// it can decode `gbk` encoding string\nquerystring.parse('w=%D6%D0%CE%C4&foo=bar', null, null,\n { decodeURIComponent: gbkDecodeURIComponent })\n// returns { w: '中文', foo: 'bar' }
\n",
"signatures": [
{
"params": [
{
"name": "str"
},
{
"name": "sep",
"optional": true
},
{
"name": "eq",
"optional": true
},
{
"name": "options",
"optional": true
}
]
}
]
},
{
"textRaw": "querystring.stringify(obj[, sep][, eq][, options])",
"type": "method",
"name": "stringify",
"desc": "Serialize an object to a query string.\nOptionally override the default separator ('&'
) and assignment ('='
)\ncharacters.\n\n
Options object may contain encodeURIComponent
property (querystring.escape
by default),\nit can be used to encode string with non-utf8
encoding if necessary.\n\n
Example:\n\n
\nquerystring.stringify({ foo: 'bar', baz: ['qux', 'quux'], corge: '' })\n// returns 'foo=bar&baz=qux&baz=quux&corge='\n\nquerystring.stringify({foo: 'bar', baz: 'qux'}, ';', ':')\n// returns 'foo:bar;baz:qux'\n\n// Suppose gbkEncodeURIComponent function already exists,\n// it can encode string with `gbk` encoding\nquerystring.stringify({ w: '中文', foo: 'bar' }, null, null,\n { encodeURIComponent: gbkEncodeURIComponent })\n// returns 'w=%D6%D0%CE%C4&foo=bar'
\n",
"signatures": [
{
"params": [
{
"name": "obj"
},
{
"name": "sep",
"optional": true
},
{
"name": "eq",
"optional": true
},
{
"name": "options",
"optional": true
}
]
}
]
}
],
"type": "module",
"displayName": "querystring"
},
{
"textRaw": "Readline",
"name": "readline",
"stability": 2,
"stabilityText": "Stable",
"desc": "To use this module, do require('readline')
. Readline allows reading of a\nstream (such as [process.stdin
][]) on a line-by-line basis.\n\n
Note that once you've invoked this module, your Node.js program will not\nterminate until you've closed the interface. Here's how to allow your\nprogram to gracefully exit:\n\n
\nconst readline = require('readline');\n\nconst rl = readline.createInterface({\n input: process.stdin,\n output: process.stdout\n});\n\nrl.question('What do you think of Node.js? ', (answer) => {\n // TODO: Log the answer in a database\n console.log('Thank you for your valuable feedback:', answer);\n\n rl.close();\n});
\n",
"classes": [
{
"textRaw": "Class: Interface",
"type": "class",
"name": "Interface",
"desc": "The class that represents a readline interface with an input and output\nstream.\n\n
\n", "methods": [ { "textRaw": "rl.close()", "type": "method", "name": "close", "desc": "Closes the Interface
instance, relinquishing control on the input
and\noutput
streams. The 'close'
event will also be emitted.\n\n
Pauses the readline input
stream, allowing it to be resumed later if needed.\n\n
Note that this doesn't immediately pause the stream of events. Several events may\nbe emitted after calling pause
, including line
.\n\n
Readies readline for input from the user, putting the current setPrompt
\noptions on a new line, giving the user a new spot to write. Set preserveCursor
\nto true
to prevent the cursor placement being reset to 0
.\n\n
This will also resume the input
stream used with createInterface
if it has\nbeen paused.\n\n
If output
is set to null
or undefined
when calling createInterface
, the\nprompt is not written.\n\n
Prepends the prompt with query
and invokes callback
with the user's\nresponse. Displays the query to the user, and then invokes callback
\nwith the user's response after it has been typed.\n\n
This will also resume the input
stream used with createInterface
if\nit has been paused.\n\n
If output
is set to null
or undefined
when calling createInterface
,\nnothing is displayed.\n\n
Example usage:\n\n
\nrl.question('What is your favorite food?', (answer) => {\n console.log(`Oh, so your favorite food is ${answer}`);\n});
\n",
"signatures": [
{
"params": [
{
"name": "query"
},
{
"name": "callback"
}
]
}
]
},
{
"textRaw": "rl.resume()",
"type": "method",
"name": "resume",
"desc": "Resumes the readline input
stream.\n\n
Sets the prompt, for example when you run node
on the command line, you see\n>
, which is Node.js's prompt.\n\n
Writes data
to output
stream, unless output
is set to null
or\nundefined
when calling createInterface
. key
is an object literal to\nrepresent a key sequence; available if the terminal is a TTY.\n\n
This will also resume the input
stream if it has been paused.\n\n
Example:\n\n
\nrl.write('Delete me!');\n// Simulate ctrl+u to delete the line written previously\nrl.write(null, {ctrl: true, name: 'u'});
\n",
"signatures": [
{
"params": [
{
"name": "data"
},
{
"name": "key",
"optional": true
}
]
}
]
}
]
}
],
"modules": [
{
"textRaw": "Events",
"name": "events",
"events": [
{
"textRaw": "Event: 'close'",
"type": "event",
"name": "close",
"desc": "function () {}
\n\n
Emitted when close()
is called.\n\n
Also emitted when the input
stream receives its 'end'
event. The Interface
\ninstance should be considered "finished" once this is emitted. For example, when\nthe input
stream receives ^D
, respectively known as EOT
.\n\n
This event is also called if there is no SIGINT
event listener present when\nthe input
stream receives a ^C
, respectively known as SIGINT
.\n\n
function (line) {}
\n\n
Emitted whenever the input
stream receives an end of line (\\n
, \\r
, or\n\\r\\n
), usually received when the user hits enter, or return. This is a good\nhook to listen for user input.\n\n
Example of listening for 'line'
:\n\n
rl.on('line', (cmd) => {\n console.log(`You just typed: ${cmd}`);\n});
\n",
"params": []
},
{
"textRaw": "Event: 'pause'",
"type": "event",
"name": "pause",
"desc": "function () {}
\n\n
Emitted whenever the input
stream is paused.\n\n
Also emitted whenever the input
stream is not paused and receives the\nSIGCONT
event. (See events SIGTSTP
and SIGCONT
)\n\n
Example of listening for 'pause'
:\n\n
rl.on('pause', () => {\n console.log('Readline paused.');\n});
\n",
"params": []
},
{
"textRaw": "Event: 'resume'",
"type": "event",
"name": "resume",
"desc": "function () {}
\n\n
Emitted whenever the input
stream is resumed.\n\n
Example of listening for 'resume'
:\n\n
rl.on('resume', () => {\n console.log('Readline resumed.');\n});
\n",
"params": []
},
{
"textRaw": "Event: 'SIGCONT'",
"type": "event",
"name": "SIGCONT",
"desc": "function () {}
\n\n
This does not work on Windows.\n\n
\nEmitted whenever the input
stream is sent to the background with ^Z
,\nrespectively known as SIGTSTP
, and then continued with fg(1)
. This event\nonly emits if the stream was not paused before sending the program to the\nbackground.\n\n
Example of listening for SIGCONT
:\n\n
rl.on('SIGCONT', () => {\n // `prompt` will automatically resume the stream\n rl.prompt();\n});
\n",
"params": []
},
{
"textRaw": "Event: 'SIGINT'",
"type": "event",
"name": "SIGINT",
"desc": "function () {}
\n\n
Emitted whenever the input
stream receives a ^C
, respectively known as\nSIGINT
. If there is no SIGINT
event listener present when the input
\nstream receives a SIGINT
, pause
will be triggered.\n\n
Example of listening for SIGINT
:\n\n
rl.on('SIGINT', () => {\n rl.question('Are you sure you want to exit?', (answer) => {\n if (answer.match(/^y(es)?$/i)) rl.pause();\n });\n});
\n",
"params": []
},
{
"textRaw": "Event: 'SIGTSTP'",
"type": "event",
"name": "SIGTSTP",
"desc": "function () {}
\n\n
This does not work on Windows.\n\n
\nEmitted whenever the input
stream receives a ^Z
, respectively known as\nSIGTSTP
. If there is no SIGTSTP
event listener present when the input
\nstream receives a SIGTSTP
, the program will be sent to the background.\n\n
When the program is resumed with fg
, the 'pause'
and SIGCONT
events will be\nemitted. You can use either to resume the stream.\n\n
The 'pause'
and SIGCONT
events will not be triggered if the stream was paused\nbefore the program was sent to the background.\n\n
Example of listening for SIGTSTP
:\n\n
rl.on('SIGTSTP', () => {\n // This will override SIGTSTP and prevent the program from going to the\n // background.\n console.log('Caught SIGTSTP.');\n});
\nHere's an example of how to use all these together to craft a tiny command\nline interface:\n\n
\nconst readline = require('readline');\nconst rl = readline.createInterface(process.stdin, process.stdout);\n\nrl.setPrompt('OHAI> ');\nrl.prompt();\n\nrl.on('line', (line) => {\n switch(line.trim()) {\n case 'hello':\n console.log('world!');\n break;\n default:\n console.log('Say what? I might have heard `' + line.trim() + '`');\n break;\n }\n rl.prompt();\n}).on('close', () => {\n console.log('Have a great day!');\n process.exit(0);\n});
\nA common case for readline
's input
option is to pass a filesystem readable\nstream to it. This is how one could craft line-by-line parsing of a file:\n\n
const readline = require('readline');\nconst fs = require('fs');\n\nconst rl = readline.createInterface({\n input: fs.createReadStream('sample.txt')\n});\n\nrl.on('line', (line) => {\n console.log('Line from file:', line);\n});
\n",
"params": []
}
],
"type": "module",
"displayName": "Events"
}
],
"methods": [
{
"textRaw": "readline.clearLine(stream, dir)",
"type": "method",
"name": "clearLine",
"desc": "Clears current line of given TTY stream in a specified direction.\ndir
should have one of following values:\n\n
-1
- to the left from cursor1
- to the right from cursor0
- the entire lineClears the screen from the current position of the cursor down.\n\n
\n", "signatures": [ { "params": [ { "name": "stream" } ] } ] }, { "textRaw": "readline.createInterface(options)", "type": "method", "name": "createInterface", "desc": "Creates a readline Interface
instance. Accepts an options
Object that takes\nthe following values:\n\n
input
- the readable stream to listen to (Required).
output
- the writable stream to write readline data to (Optional).
completer
- an optional function that is used for Tab autocompletion. See\nbelow for an example of using this.
terminal
- pass true
if the input
and output
streams should be\ntreated like a TTY, and have ANSI/VT100 escape codes written to it.\nDefaults to checking isTTY
on the output
stream upon instantiation.
historySize
- maximum number of history lines retained. To disable the\nhistory set this value to 0
. Defaults to 30
. This option makes sense\nonly if terminal
is set to true
by the user or by an internal output
\ncheck, otherwise the history caching mechanism is not initialized at all.
The completer
function is given the current line entered by the user, and\nis supposed to return an Array with 2 entries:\n\n
An Array with matching entries for the completion.
\nThe substring that was used for the matching.
\nWhich ends up looking something like:\n[[substr1, substr2, ...], originalsubstring]
.\n\n
Example:\n\n
\nfunction completer(line) {\n var completions = '.help .error .exit .quit .q'.split(' ')\n var hits = completions.filter((c) => { return c.indexOf(line) == 0 })\n // show all completions if none found\n return [hits.length ? hits : completions, line]\n}
\nAlso completer
can be run in async mode if it accepts two arguments:\n\n
function completer(linePartial, callback) {\n callback(null, [['123'], linePartial]);\n}
\ncreateInterface
is commonly used with [process.stdin
][] and\n[process.stdout
][] in order to accept user input:\n\n
const readline = require('readline');\nconst rl = readline.createInterface({\n input: process.stdin,\n output: process.stdout\n});
\nOnce you have a readline instance, you most commonly listen for the\n'line'
event.\n\n
If terminal
is true
for this instance then the output
stream will get\nthe best compatibility if it defines an output.columns
property, and fires\na 'resize'
event on the output
if/when the columns ever change\n([process.stdout
][] does this automatically when it is a TTY).\n\n
Move cursor to the specified position in a given TTY stream.\n\n
\n", "signatures": [ { "params": [ { "name": "stream" }, { "name": "x" }, { "name": "y" } ] } ] }, { "textRaw": "readline.emitKeypressEvents(stream)", "type": "method", "name": "emitKeypressEvents", "desc": "Causes stream
to begin emitting 'keypress'
events corresponding to its\ninput.\n\n
Move cursor relative to it's current position in a given TTY stream.\n\n
\n", "signatures": [ { "params": [ { "name": "stream" }, { "name": "dx" }, { "name": "dy" } ] } ] } ], "type": "module", "displayName": "Readline" }, { "textRaw": "REPL", "name": "repl", "stability": 2, "stabilityText": "Stable", "desc": "A Read-Eval-Print-Loop (REPL) is available both as a standalone program and\neasily includable in other programs. The REPL provides a way to interactively\nrun JavaScript and see the results. It can be used for debugging, testing, or\njust trying things out.\n\n
\nBy executing node
without any arguments from the command-line you will be\ndropped into the REPL. It has simplistic emacs line-editing.\n\n
$ node\nType '.help' for options.\n> a = [1, 2, 3];\n[ 1, 2, 3 ]\n> a.forEach((v) => {\n... console.log(v);\n... });\n1\n2\n3
\nFor advanced line-editors, start Node.js with the environmental variable\nNODE_NO_READLINE=1
. This will start the main and debugger REPL in canonical\nterminal settings which will allow you to use with rlwrap
.\n\n
For example, you could add this to your bashrc file:\n\n
\nalias node="env NODE_NO_READLINE=1 rlwrap node"
\n",
"modules": [
{
"textRaw": "Environment Variable Options",
"name": "environment_variable_options",
"desc": "The built-in repl (invoked by running node
or node -i
) may be controlled\nvia the following environment variables:\n\n
NODE_REPL_HISTORY
- When a valid path is given, persistent REPL history\nwill be saved to the specified file rather than .node_repl_history
in the\nuser's home directory. Setting this value to ""
will disable persistent\nREPL history. Whitespace will be trimmed from the value.NODE_REPL_HISTORY_SIZE
- Defaults to 1000
. Controls how many lines of\nhistory will be persisted if history is available. Must be a positive number.NODE_REPL_MODE
- May be any of sloppy
, strict
, or magic
. Defaults\nto magic
, which will automatically run "strict mode only" statements in\nstrict mode.By default, the REPL will persist history between node
REPL sessions by saving\nto a .node_repl_history
file in the user's home directory. This can be\ndisabled by setting the environment variable NODE_REPL_HISTORY=""
.\n\n
Previously in Node.js/io.js v2.x, REPL history was controlled by using a\nNODE_REPL_HISTORY_FILE
environment variable, and the history was saved in JSON\nformat. This variable has now been deprecated, and your REPL history will\nautomatically be converted to using plain text. The new file will be saved to\neither your home directory, or a directory defined by the NODE_REPL_HISTORY
\nvariable, as documented here.\n\n
Inside the REPL, Control+D will exit. Multi-line expressions can be input.\nTab completion is supported for both global and local variables.\n\n
\nCore modules will be loaded on-demand into the environment. For example,\naccessing fs
will require()
the fs
module as global.fs
.\n\n
The special variable _
(underscore) contains the result of the last expression.\n\n
> [ 'a', 'b', 'c' ]\n[ 'a', 'b', 'c' ]\n> _.length\n3\n> _ += 1\n4
\nExplicitly setting _
will disable this behavior until the context is reset.\n\n
The REPL provides access to any variables in the global scope. You can expose\na variable to the REPL explicitly by assigning it to the context
object\nassociated with each REPLServer
. For example:\n\n
// repl_test.js\nconst repl = require('repl');\nvar msg = 'message';\n\nrepl.start('> ').context.m = msg;
\nThings in the context
object appear as local within the REPL:\n\n
$ node repl_test.js\n> m\n'message'
\nThere are a few special REPL commands:\n\n
\n.break
- While inputting a multi-line expression, sometimes you get lost\nor just don't care about completing it. .break
will start over..clear
- Resets the context
object to an empty object and clears any\nmulti-line expression..exit
- Close the I/O stream, which will cause the REPL to exit..help
- Show this list of special commands..save
- Save the current REPL session to a file\n\n.save ./file/to/save.js
\n
.load
- Load a file into the current REPL session.\n\n.load ./file/to/load.js
\n
The following key combinations in the REPL have these special effects:\n\n
\n<ctrl>C
- Similar to the .break
keyword. Terminates the current\ncommand. Press twice on a blank line to forcibly exit.<ctrl>D
- Similar to the .exit
keyword.<tab>
- Show both global and local(scope) variablesThe REPL module internally uses\n[util.inspect()
][], when printing values. However, util.inspect
delegates the\n call to the object's inspect()
function, if it has one. You can read more\n about this delegation [here][].\n\n
For example, if you have defined an inspect()
function on an object, like this:\n\n
> var obj = {foo: 'this will not show up in the inspect() output'};\nundefined\n> obj.inspect = () => {\n... return {bar: 'baz'};\n... };\n[Function]
\nand try to print obj
in REPL, it will invoke the custom inspect()
function:\n\n
> obj\n{bar: 'baz'}
\n",
"type": "misc",
"displayName": "Customizing Object displays in the REPL"
}
]
}
],
"classes": [
{
"textRaw": "Class: REPLServer",
"type": "class",
"name": "REPLServer",
"desc": "This inherits from [Readline Interface][] with the following events:\n\n
\n", "events": [ { "textRaw": "Event: 'exit'", "type": "event", "name": "exit", "desc": "function () {}
\n\n
Emitted when the user exits the REPL in any of the defined ways. Namely, typing\n.exit
at the repl, pressing Ctrl+C twice to signal SIGINT
, or pressing Ctrl+D\nto signal 'end'
on the input
stream.\n\n
Example of listening for exit
:\n\n
replServer.on('exit', () => {\n console.log('Got "exit" event from repl!');\n process.exit();\n});
\n",
"params": []
},
{
"textRaw": "Event: 'reset'",
"type": "event",
"name": "reset",
"desc": "function (context) {}
\n\n
Emitted when the REPL's context is reset. This happens when you type .clear
.\nIf you start the repl with { useGlobal: true }
then this event will never\nbe emitted.\n\n
Example of listening for reset
:\n\n
// Extend the initial repl context.\nvar replServer = repl.start({ options ... });\nsomeExtension.extend(r.context);\n\n// When a new context is created extend it as well.\nreplServer.on('reset', (context) => {\n console.log('repl has a new context');\n someExtension.extend(context);\n});
\n",
"params": []
}
],
"methods": [
{
"textRaw": "replServer.defineCommand(keyword, cmd)",
"type": "method",
"name": "defineCommand",
"signatures": [
{
"params": [
{
"textRaw": "`keyword` {String} ",
"name": "keyword",
"type": "String"
},
{
"textRaw": "`cmd` {Object|Function} ",
"name": "cmd",
"type": "Object|Function"
}
]
},
{
"params": [
{
"name": "keyword"
},
{
"name": "cmd"
}
]
}
],
"desc": "Makes a command available in the REPL. The command is invoked by typing a .
\nfollowed by the keyword. The cmd
is an object with the following values:\n\n
help
- help text to be displayed when .help
is entered (Optional).action
- a function to execute, potentially taking in a string argument,\nwhen the command is invoked, bound to the REPLServer instance (Required).If a function is provided instead of an object for cmd
, it is treated as the\naction
.\n\n
Example of defining a command:\n\n
\n// repl_test.js\nconst repl = require('repl');\n\nvar replServer = repl.start();\nreplServer.defineCommand('sayhello', {\n help: 'Say hello',\n action: function(name) {\n this.write(`Hello, ${name}!\\n`);\n this.displayPrompt();\n }\n});
\nExample of invoking that command from the REPL:\n\n
\n> .sayhello Node.js User\nHello, Node.js User!
\n"
},
{
"textRaw": "replServer.displayPrompt([preserveCursor])",
"type": "method",
"name": "displayPrompt",
"signatures": [
{
"params": [
{
"textRaw": "`preserveCursor` {Boolean} ",
"name": "preserveCursor",
"type": "Boolean",
"optional": true
}
]
},
{
"params": [
{
"name": "preserveCursor",
"optional": true
}
]
}
],
"desc": "Like [readline.prompt
][] except also adding indents with ellipses when inside\nblocks. The preserveCursor
argument is passed to [readline.prompt
][]. This is\nused primarily with defineCommand
. It's also used internally to render each\nprompt line.\n\n
Returns and starts a REPLServer
instance, that inherits from\n[Readline Interface][]. Accepts an "options" Object that takes\nthe following values:\n\n
prompt
- the prompt and stream
for all I/O. Defaults to >
.
input
- the readable stream to listen to. Defaults to process.stdin
.
output
- the writable stream to write readline data to. Defaults to\nprocess.stdout
.
terminal
- pass true
if the stream
should be treated like a TTY, and\nhave ANSI/VT100 escape codes written to it. Defaults to checking isTTY
\non the output
stream upon instantiation.
eval
- function that will be used to eval each given line. Defaults to\nan async wrapper for eval()
. See below for an example of a custom eval
.
useColors
- a boolean which specifies whether or not the writer
function\nshould output colors. If a different writer
function is set then this does\nnothing. Defaults to the repl's terminal
value.
useGlobal
- if set to true
, then the repl will use the global
object,\ninstead of running scripts in a separate context. Defaults to false
.
ignoreUndefined
- if set to true
, then the repl will not output the\nreturn value of command if it's undefined
. Defaults to false
.
writer
- the function to invoke for each command that gets evaluated which\nreturns the formatting (including coloring) to display. Defaults to\nutil.inspect
.
replMode
- controls whether the repl runs all commands in strict mode,\ndefault mode, or a hybrid mode ("magic" mode.) Acceptable values are:
repl.REPL_MODE_SLOPPY
- run commands in sloppy mode.repl.REPL_MODE_STRICT
- run commands in strict mode. This is equivalent to\nprefacing every repl statement with 'use strict'
.repl.REPL_MODE_MAGIC
- attempt to run commands in default mode. If they\nfail to parse, re-try in strict mode.You can use your own eval
function if it has following signature:\n\n
function eval(cmd, context, filename, callback) {\n callback(null, result);\n}
\nOn tab completion, eval
will be called with .scope
as an input string. It\nis expected to return an array of scope names to be used for the auto-completion.\n\n
Multiple REPLs may be started against the same running instance of Node.js. Each\nwill share the same global object but will have unique I/O.\n\n
\nHere is an example that starts a REPL on stdin, a Unix socket, and a TCP socket:\n\n
\nconst net = require('net');\nconst repl = require('repl');\nvar connections = 0;\n\nrepl.start({\n prompt: 'Node.js via stdin> ',\n input: process.stdin,\n output: process.stdout\n});\n\nnet.createServer((socket) => {\n connections += 1;\n repl.start({\n prompt: 'Node.js via Unix socket> ',\n input: socket,\n output: socket\n }).on('exit', () => {\n socket.end();\n })\n}).listen('/tmp/node-repl-sock');\n\nnet.createServer((socket) => {\n connections += 1;\n repl.start({\n prompt: 'Node.js via TCP socket> ',\n input: socket,\n output: socket\n }).on('exit', () => {\n socket.end();\n });\n}).listen(5001);
\nRunning this program from the command line will start a REPL on stdin. Other\nREPL clients may connect through the Unix socket or TCP socket. telnet
is useful\nfor connecting to TCP sockets, and socat
can be used to connect to both Unix and\nTCP sockets.\n\n
By starting a REPL from a Unix socket-based server instead of stdin, you can\nconnect to a long-running Node.js process without restarting it.\n\n
\nFor an example of running a "full-featured" (terminal
) REPL over\na net.Server
and net.Socket
instance, see: https://gist.github.com/2209310\n\n
For an example of running a REPL instance over curl(1)
,\nsee: https://gist.github.com/2053342\n\n
A stream is an abstract interface implemented by various objects in\nNode.js. For example a [request to an HTTP server][http-incoming-message] is a\nstream, as is [process.stdout
][]. Streams are readable, writable, or both. All\nstreams are instances of [EventEmitter
][].\n\n
You can load the Stream base classes by doing require('stream')
.\nThere are base classes provided for [Readable][] streams, [Writable][]\nstreams, [Duplex][] streams, and [Transform][] streams.\n\n
This document is split up into 3 sections:\n\n
\nDuplex streams are streams that implement both the [Readable][] and\n[Writable][] interfaces.\n\n
\nExamples of Duplex streams include:\n\n
\nThe Readable stream interface is the abstraction for a source of\ndata that you are reading from. In other words, data comes out of a\nReadable stream.\n\n
\nA Readable stream will not start emitting data until you indicate that\nyou are ready to receive it.\n\n
\nReadable streams have two "modes": a flowing mode and a paused\nmode. When in flowing mode, data is read from the underlying system\nand provided to your program as fast as possible. In paused mode, you\nmust explicitly call [stream.read()
][stream-read] to get chunks of data out.\nStreams start out in paused mode.\n\n
Note: If no data event handlers are attached, and there are no\n[stream.pipe()
][] destinations, and the stream is switched into flowing\nmode, then data will be lost.\n\n
You can switch to flowing mode by doing any of the following:\n\n
\n'data'
][] event handler to listen for data.stream.resume()
][stream-resume] method to explicitly open the\nflow.stream.pipe()
][] method to send the data to a [Writable][].You can switch back to paused mode by doing either of the following:\n\n
\nstream.pause()
][stream-pause] method.'data'
][] event\nhandlers, and removing all pipe destinations by calling the\n[stream.unpipe()
][] method.Note that, for backwards compatibility reasons, removing ['data'
][]\nevent handlers will not automatically pause the stream. Also, if\nthere are piped destinations, then calling [stream.pause()
][stream-pause] will\nnot guarantee that the stream will remain paused once those\ndestinations drain and ask for more data.\n\n
Examples of readable streams include:\n\n
\nprocess.stdin
][]Emitted when the stream and any of its underlying resources (a file\ndescriptor, for example) have been closed. The event indicates that\nno more events will be emitted, and no further computation will occur.\n\n
\nNot all streams will emit the 'close'
event as the 'close'
event is\noptional.\n\n
Attaching a 'data'
event listener to a stream that has not been\nexplicitly paused will switch the stream into flowing mode. Data will\nthen be passed as soon as it is available.\n\n
If you just want to get all the data out of the stream as fast as\npossible, this is the best way to do so.\n\n
\nvar readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log('got %d bytes of data', chunk.length);\n});
\n"
},
{
"textRaw": "Event: 'end'",
"type": "event",
"name": "end",
"desc": "This event fires when there will be no more data to read.\n\n
\nNote that the 'end'
event will not fire unless the data is\ncompletely consumed. This can be done by switching into flowing mode,\nor by calling [stream.read()
][stream-read] repeatedly until you get to the\nend.\n\n
var readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log('got %d bytes of data', chunk.length);\n});\nreadable.on('end', () => {\n console.log('there will be no more data.');\n});
\n",
"params": []
},
{
"textRaw": "Event: 'error'",
"type": "event",
"name": "error",
"params": [],
"desc": "Emitted if there was an error receiving data.\n\n
\n" }, { "textRaw": "Event: 'readable'", "type": "event", "name": "readable", "desc": "When a chunk of data can be read from the stream, it will emit a\n'readable'
event.\n\n
In some cases, listening for a 'readable'
event will cause some data\nto be read into the internal buffer from the underlying system, if it\nhadn't already.\n\n
var readable = getReadableStreamSomehow();\nreadable.on('readable', () => {\n // there is some data to read now\n});
\nOnce the internal buffer is drained, a 'readable'
event will fire\nagain when more data is available.\n\n
The 'readable'
event is not emitted in the "flowing" mode with the\nsole exception of the last one, on end-of-stream.\n\n
The 'readable'
event indicates that the stream has new information:\neither new data is available or the end of the stream has been reached.\nIn the former case, [stream.read()
][stream-read] will return that data. In the\nlatter case, [stream.read()
][stream-read] will return null. For instance, in\nthe following example, foo.txt
is an empty file:\n\n
const fs = require('fs');\nvar rr = fs.createReadStream('foo.txt');\nrr.on('readable', () => {\n console.log('readable:', rr.read());\n});\nrr.on('end', () => {\n console.log('end');\n});
\nThe output of running this script is:\n\n
\n$ node test.js\nreadable: null\nend
\n",
"params": []
}
],
"methods": [
{
"textRaw": "readable.isPaused()",
"type": "method",
"name": "isPaused",
"signatures": [
{
"return": {
"textRaw": "Return: {Boolean} ",
"name": "return",
"type": "Boolean"
},
"params": []
},
{
"params": []
}
],
"desc": "This method returns whether or not the readable
has been explicitly\npaused by client code (using [stream.pause()
][stream-pause] without a\ncorresponding [stream.resume()
][stream-resume]).\n\n
var readable = new stream.Readable\n\nreadable.isPaused() // === false\nreadable.pause()\nreadable.isPaused() // === true\nreadable.resume()\nreadable.isPaused() // === false
\n"
},
{
"textRaw": "readable.pause()",
"type": "method",
"name": "pause",
"signatures": [
{
"return": {
"textRaw": "Return: `this` ",
"name": "return",
"desc": "`this`"
},
"params": []
},
{
"params": []
}
],
"desc": "This method will cause a stream in flowing mode to stop emitting\n['data'
][] events, switching out of flowing mode. Any data that becomes\navailable will remain in the internal buffer.\n\n
var readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log('got %d bytes of data', chunk.length);\n readable.pause();\n console.log('there will be no more data for 1 second');\n setTimeout(() => {\n console.log('now data will start flowing again');\n readable.resume();\n }, 1000);\n});
\n"
},
{
"textRaw": "readable.pipe(destination[, options])",
"type": "method",
"name": "pipe",
"signatures": [
{
"params": [
{
"textRaw": "`destination` {stream.Writable} The destination for writing data ",
"name": "destination",
"type": "stream.Writable",
"desc": "The destination for writing data"
},
{
"textRaw": "`options` {Object} Pipe options ",
"options": [
{
"textRaw": "`end` {Boolean} End the writer when the reader ends. Default = `true` ",
"name": "end",
"type": "Boolean",
"desc": "End the writer when the reader ends. Default = `true`"
}
],
"name": "options",
"type": "Object",
"desc": "Pipe options",
"optional": true
}
]
},
{
"params": [
{
"name": "destination"
},
{
"name": "options",
"optional": true
}
]
}
],
"desc": "This method pulls all the data out of a readable stream, and writes it\nto the supplied destination, automatically managing the flow so that\nthe destination is not overwhelmed by a fast readable stream.\n\n
\nMultiple destinations can be piped to safely.\n\n
\nvar readable = getReadableStreamSomehow();\nvar writable = fs.createWriteStream('file.txt');\n// All the data from readable goes into 'file.txt'\nreadable.pipe(writable);
\nThis function returns the destination stream, so you can set up pipe\nchains like so:\n\n
\nvar r = fs.createReadStream('file.txt');\nvar z = zlib.createGzip();\nvar w = fs.createWriteStream('file.txt.gz');\nr.pipe(z).pipe(w);
\nFor example, emulating the Unix cat
command:\n\n
process.stdin.pipe(process.stdout);
\nBy default [stream.end()
][stream-end] is called on the destination when the\nsource stream emits ['end'
][], so that destination
is no longer writable.\nPass { end: false }
as options
to keep the destination stream open.\n\n
This keeps writer
open so that "Goodbye" can be written at the\nend.\n\n
reader.pipe(writer, { end: false });\nreader.on('end', () => {\n writer.end('Goodbye\\n');\n});
\nNote that [process.stderr
][] and [process.stdout
][] are never closed until\nthe process exits, regardless of the specified options.\n\n
The read()
method pulls some data out of the internal buffer and\nreturns it. If there is no data available, then it will return\nnull
.\n\n
If you pass in a size
argument, then it will return that many\nbytes. If size
bytes are not available, then it will return null
,\nunless we've ended, in which case it will return the data remaining\nin the buffer.\n\n
If you do not specify a size
argument, then it will return all the\ndata in the internal buffer.\n\n
This method should only be called in paused mode. In flowing mode,\nthis method is called automatically until the internal buffer is\ndrained.\n\n
\nvar readable = getReadableStreamSomehow();\nreadable.on('readable', () => {\n var chunk;\n while (null !== (chunk = readable.read())) {\n console.log('got %d bytes of data', chunk.length);\n }\n});
\nIf this method returns a data chunk, then it will also trigger the\nemission of a ['data'
][] event.\n\n
Note that calling [stream.read([size])
][stream-read] after the ['end'
][]\nevent has been triggered will return null
. No runtime error will be raised.\n\n
This method will cause the readable stream to resume emitting ['data'
][]\nevents.\n\n
This method will switch the stream into flowing mode. If you do not\nwant to consume the data from a stream, but you do want to get to\nits ['end'
][] event, you can call [stream.resume()
][stream-resume] to open\nthe flow of data.\n\n
var readable = getReadableStreamSomehow();\nreadable.resume();\nreadable.on('end', () => {\n console.log('got to the end, but did not read anything');\n});
\n"
},
{
"textRaw": "readable.setEncoding(encoding)",
"type": "method",
"name": "setEncoding",
"signatures": [
{
"return": {
"textRaw": "Return: `this` ",
"name": "return",
"desc": "`this`"
},
"params": [
{
"textRaw": "`encoding` {String} The encoding to use. ",
"name": "encoding",
"type": "String",
"desc": "The encoding to use."
}
]
},
{
"params": [
{
"name": "encoding"
}
]
}
],
"desc": "Call this function to cause the stream to return strings of the specified\nencoding instead of Buffer objects. For example, if you do\nreadable.setEncoding('utf8')
, then the output data will be interpreted as\nUTF-8 data, and returned as strings. If you do readable.setEncoding('hex')
,\nthen the data will be encoded in hexadecimal string format.\n\n
This properly handles multi-byte characters that would otherwise be\npotentially mangled if you simply pulled the Buffers directly and\ncalled [buf.toString(encoding)
][] on them. If you want to read the data\nas strings, always use this method.\n\n
Also you can disable any encoding at all with readable.setEncoding(null)
.\nThis approach is very useful if you deal with binary data or with large\nmulti-byte strings spread out over multiple chunks.\n\n
var readable = getReadableStreamSomehow();\nreadable.setEncoding('utf8');\nreadable.on('data', (chunk) => {\n assert.equal(typeof chunk, 'string');\n console.log('got %d characters of string data', chunk.length);\n});
\n"
},
{
"textRaw": "readable.unpipe([destination])",
"type": "method",
"name": "unpipe",
"signatures": [
{
"params": [
{
"textRaw": "`destination` {stream.Writable} Optional specific stream to unpipe ",
"name": "destination",
"type": "stream.Writable",
"desc": "Optional specific stream to unpipe",
"optional": true
}
]
},
{
"params": [
{
"name": "destination",
"optional": true
}
]
}
],
"desc": "This method will remove the hooks set up for a previous [stream.pipe()
][]\ncall.\n\n
If the destination is not specified, then all pipes are removed.\n\n
\nIf the destination is specified, but no pipe is set up for it, then\nthis is a no-op.\n\n
\nvar readable = getReadableStreamSomehow();\nvar writable = fs.createWriteStream('file.txt');\n// All the data from readable goes into 'file.txt',\n// but only for the first second\nreadable.pipe(writable);\nsetTimeout(() => {\n console.log('stop writing to file.txt');\n readable.unpipe(writable);\n console.log('manually close the file stream');\n writable.end();\n}, 1000);
\n"
},
{
"textRaw": "readable.unshift(chunk)",
"type": "method",
"name": "unshift",
"signatures": [
{
"params": [
{
"textRaw": "`chunk` {Buffer|String} Chunk of data to unshift onto the read queue ",
"name": "chunk",
"type": "Buffer|String",
"desc": "Chunk of data to unshift onto the read queue"
}
]
},
{
"params": [
{
"name": "chunk"
}
]
}
],
"desc": "This is useful in certain cases where a stream is being consumed by a\nparser, which needs to "un-consume" some data that it has\noptimistically pulled out of the source, so that the stream can be\npassed on to some other party.\n\n
\nNote that stream.unshift(chunk)
cannot be called after the ['end'
][] event\nhas been triggered; a runtime error will be raised.\n\n
If you find that you must often call stream.unshift(chunk)
in your\nprograms, consider implementing a [Transform][] stream instead. (See [API\nfor Stream Implementors][].)\n\n
// Pull off a header delimited by \\n\\n\n// use unshift() if we get too much\n// Call the callback with (error, header, stream)\nconst StringDecoder = require('string_decoder').StringDecoder;\nfunction parseHeader(stream, callback) {\n stream.on('error', callback);\n stream.on('readable', onReadable);\n var decoder = new StringDecoder('utf8');\n var header = '';\n function onReadable() {\n var chunk;\n while (null !== (chunk = stream.read())) {\n var str = decoder.write(chunk);\n if (str.match(/\\n\\n/)) {\n // found the header boundary\n var split = str.split(/\\n\\n/);\n header += split.shift();\n var remaining = split.join('\\n\\n');\n var buf = Buffer.from(remaining, 'utf8');\n if (buf.length)\n stream.unshift(buf);\n stream.removeListener('error', callback);\n stream.removeListener('readable', onReadable);\n // now the body of the message can be read from the stream.\n callback(null, header, stream);\n } else {\n // still reading the header.\n header += str;\n }\n }\n }\n}
\nNote that, unlike [stream.push(chunk)
][stream-push], stream.unshift(chunk)
\nwill not end the reading process by resetting the internal reading state of the\nstream. This can cause unexpected results if unshift()
is called during a\nread (i.e. from within a [stream._read()
][stream-_read] implementation on a\ncustom stream). Following the call to unshift()
with an immediate\n[stream.push('')
][stream-push] will reset the reading state appropriately,\nhowever it is best to simply avoid calling unshift()
while in the process of\nperforming a read.\n\n
Versions of Node.js prior to v0.10 had streams that did not implement the\nentire Streams API as it is today. (See [Compatibility][] for\nmore information.)\n\n
\nIf you are using an older Node.js library that emits ['data'
][] events and\nhas a [stream.pause()
][stream-pause] method that is advisory only, then you\ncan use the wrap()
method to create a [Readable][] stream that uses the old\nstream as its data source.\n\n
You will very rarely ever need to call this function, but it exists\nas a convenience for interacting with old Node.js programs and libraries.\n\n
\nFor example:\n\n
\nconst OldReader = require('./old-api-module.js').OldReader;\nconst Readable = require('stream').Readable;\nconst oreader = new OldReader;\nconst myReader = new Readable().wrap(oreader);\n\nmyReader.on('readable', () => {\n myReader.read(); // etc.\n});
\n"
}
]
},
{
"textRaw": "Class: stream.Transform",
"type": "class",
"name": "stream.Transform",
"desc": "Transform streams are [Duplex][] streams where the output is in some way\ncomputed from the input. They implement both the [Readable][] and\n[Writable][] interfaces.\n\n
\nExamples of Transform streams include:\n\n
\nThe Writable stream interface is an abstraction for a destination\nthat you are writing data to.\n\n
\nExamples of writable streams include:\n\n
\nprocess.stdout
][], [process.stderr
][]Emitted when the stream and any of its underlying resources (a file descriptor,\nfor example) have been closed. The event indicates that no more events will be\nemitted, and no further computation will occur.\n\n
\nNot all streams will emit the 'close'
event as the 'close'
event is\noptional.\n\n
If a [stream.write(chunk)
][stream-write] call returns false
, then the\n'drain'
event will indicate when it is appropriate to begin writing more data\nto the stream.\n\n
// Write the data to the supplied writable stream one million times.\n// Be attentive to back-pressure.\nfunction writeOneMillionTimes(writer, data, encoding, callback) {\n var i = 1000000;\n write();\n function write() {\n var ok = true;\n do {\n i -= 1;\n if (i === 0) {\n // last time!\n writer.write(data, encoding, callback);\n } else {\n // see if we should continue, or wait\n // don't pass the callback, because we're not done yet.\n ok = writer.write(data, encoding);\n }\n } while (i > 0 && ok);\n if (i > 0) {\n // had to stop early!\n // write some more once it drains\n writer.once('drain', write);\n }\n }\n}
\n",
"params": []
},
{
"textRaw": "Event: 'error'",
"type": "event",
"name": "error",
"params": [],
"desc": "Emitted if there was an error when writing or piping data.\n\n
\n" }, { "textRaw": "Event: 'finish'", "type": "event", "name": "finish", "desc": "When the [stream.end()
][stream-end] method has been called, and all data has\nbeen flushed to the underlying system, this event is emitted.\n\n
var writer = getWritableStreamSomehow();\nfor (var i = 0; i < 100; i ++) {\n writer.write('hello, #${i}!\\n');\n}\nwriter.end('this is the end\\n');\nwriter.on('finish', () => {\n console.error('all writes are now complete.');\n});
\n",
"params": []
},
{
"textRaw": "Event: 'pipe'",
"type": "event",
"name": "pipe",
"params": [],
"desc": "This is emitted whenever the [stream.pipe()
][] method is called on a readable\nstream, adding this writable to its set of destinations.\n\n
var writer = getWritableStreamSomehow();\nvar reader = getReadableStreamSomehow();\nwriter.on('pipe', (src) => {\n console.error('something is piping into the writer');\n assert.equal(src, reader);\n});\nreader.pipe(writer);
\n"
},
{
"textRaw": "Event: 'unpipe'",
"type": "event",
"name": "unpipe",
"params": [],
"desc": "This is emitted whenever the [stream.unpipe()
][] method is called on a\nreadable stream, removing this writable from its set of destinations.\n\n
var writer = getWritableStreamSomehow();\nvar reader = getReadableStreamSomehow();\nwriter.on('unpipe', (src) => {\n console.error('something has stopped piping into the writer');\n assert.equal(src, reader);\n});\nreader.pipe(writer);\nreader.unpipe(writer);
\n"
}
],
"methods": [
{
"textRaw": "writable.cork()",
"type": "method",
"name": "cork",
"desc": "Forces buffering of all writes.\n\n
\nBuffered data will be flushed either at [stream.uncork()
][] or at\n[stream.end()
][stream-end] call.\n\n
Call this method when no more data will be written to the stream. If supplied,\nthe callback is attached as a listener on the ['finish'
][] event.\n\n
Calling [stream.write()
][stream-write] after calling\n[stream.end()
][stream-end] will raise an error.\n\n
// write 'hello, ' and then end with 'world!'\nvar file = fs.createWriteStream('example.txt');\nfile.write('hello, ');\nfile.end('world!');\n// writing more now is not allowed!
\n"
},
{
"textRaw": "writable.setDefaultEncoding(encoding)",
"type": "method",
"name": "setDefaultEncoding",
"signatures": [
{
"return": {
"textRaw": "Return: `this` ",
"name": "return",
"desc": "`this`"
},
"params": [
{
"textRaw": "`encoding` {String} The new default encoding ",
"name": "encoding",
"type": "String",
"desc": "The new default encoding"
}
]
},
{
"params": [
{
"name": "encoding"
}
]
}
],
"desc": "Sets the default encoding for a writable stream.\n\n
\n" }, { "textRaw": "writable.uncork()", "type": "method", "name": "uncork", "desc": "Flush all data, buffered since [stream.cork()
][] call.\n\n
This method writes some data to the underlying system, and calls the\nsupplied callback once the data has been fully handled. If an error\noccurs, the callback may or may not be called with the error as its\nfirst argument. To detect write errors, listen for the 'error'
event.\n\n
The return value indicates if you should continue writing right now.\nIf the data had to be buffered internally, then it will return\nfalse
. Otherwise, it will return true
.\n\n
This return value is strictly advisory. You MAY continue to write,\neven if it returns false
. However, writes will be buffered in\nmemory, so it is best not to do this excessively. Instead, wait for\nthe ['drain'
][] event before writing more data.\n\n\n
Streams can be either [Readable][], [Writable][], or both ([Duplex][]).\n\n
\nAll streams are EventEmitters, but they also have other custom methods\nand properties depending on whether they are Readable, Writable, or\nDuplex.\n\n
\nIf a stream is both Readable and Writable, then it implements all of\nthe methods and events. So, a [Duplex][] or [Transform][] stream is\nfully described by this API, though their implementation may be\nsomewhat different.\n\n
\nIt is not necessary to implement Stream interfaces in order to consume\nstreams in your programs. If you are implementing streaming\ninterfaces in your own program, please also refer to\n[API for Stream Implementors][].\n\n
\nAlmost all Node.js programs, no matter how simple, use Streams in some\nway. Here is an example of using Streams in an Node.js program:\n\n
\nconst http = require('http');\n\nvar server = http.createServer( (req, res) => {\n // req is an http.IncomingMessage, which is a Readable Stream\n // res is an http.ServerResponse, which is a Writable Stream\n\n var body = '';\n // we want to get the data as utf8 strings\n // If you don't set an encoding, then you'll get Buffer objects\n req.setEncoding('utf8');\n\n // Readable streams emit 'data' events once a listener is added\n req.on('data', (chunk) => {\n body += chunk;\n });\n\n // the end event tells you that you have entire body\n req.on('end', () => {\n try {\n var data = JSON.parse(body);\n } catch (er) {\n // uh oh! bad json!\n res.statusCode = 400;\n return res.end(`error: ${er.message}`);\n }\n\n // write back something interesting to the user:\n res.write(typeof data);\n res.end();\n });\n});\n\nserver.listen(1337);\n\n// $ curl localhost:1337 -d '{}'\n// object\n// $ curl localhost:1337 -d '"foo"'\n// string\n// $ curl localhost:1337 -d 'not json'\n// error: Unexpected token o
\n",
"classes": [
{
"textRaw": "Class: stream.Duplex",
"type": "class",
"name": "stream.Duplex",
"desc": "Duplex streams are streams that implement both the [Readable][] and\n[Writable][] interfaces.\n\n
\nExamples of Duplex streams include:\n\n
\nThe Readable stream interface is the abstraction for a source of\ndata that you are reading from. In other words, data comes out of a\nReadable stream.\n\n
\nA Readable stream will not start emitting data until you indicate that\nyou are ready to receive it.\n\n
\nReadable streams have two "modes": a flowing mode and a paused\nmode. When in flowing mode, data is read from the underlying system\nand provided to your program as fast as possible. In paused mode, you\nmust explicitly call [stream.read()
][stream-read] to get chunks of data out.\nStreams start out in paused mode.\n\n
Note: If no data event handlers are attached, and there are no\n[stream.pipe()
][] destinations, and the stream is switched into flowing\nmode, then data will be lost.\n\n
You can switch to flowing mode by doing any of the following:\n\n
\n'data'
][] event handler to listen for data.stream.resume()
][stream-resume] method to explicitly open the\nflow.stream.pipe()
][] method to send the data to a [Writable][].You can switch back to paused mode by doing either of the following:\n\n
\nstream.pause()
][stream-pause] method.'data'
][] event\nhandlers, and removing all pipe destinations by calling the\n[stream.unpipe()
][] method.Note that, for backwards compatibility reasons, removing ['data'
][]\nevent handlers will not automatically pause the stream. Also, if\nthere are piped destinations, then calling [stream.pause()
][stream-pause] will\nnot guarantee that the stream will remain paused once those\ndestinations drain and ask for more data.\n\n
Examples of readable streams include:\n\n
\nprocess.stdin
][]Emitted when the stream and any of its underlying resources (a file\ndescriptor, for example) have been closed. The event indicates that\nno more events will be emitted, and no further computation will occur.\n\n
\nNot all streams will emit the 'close'
event as the 'close'
event is\noptional.\n\n
Attaching a 'data'
event listener to a stream that has not been\nexplicitly paused will switch the stream into flowing mode. Data will\nthen be passed as soon as it is available.\n\n
If you just want to get all the data out of the stream as fast as\npossible, this is the best way to do so.\n\n
\nvar readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log('got %d bytes of data', chunk.length);\n});
\n"
},
{
"textRaw": "Event: 'end'",
"type": "event",
"name": "end",
"desc": "This event fires when there will be no more data to read.\n\n
\nNote that the 'end'
event will not fire unless the data is\ncompletely consumed. This can be done by switching into flowing mode,\nor by calling [stream.read()
][stream-read] repeatedly until you get to the\nend.\n\n
var readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log('got %d bytes of data', chunk.length);\n});\nreadable.on('end', () => {\n console.log('there will be no more data.');\n});
\n",
"params": []
},
{
"textRaw": "Event: 'error'",
"type": "event",
"name": "error",
"params": [],
"desc": "Emitted if there was an error receiving data.\n\n
\n" }, { "textRaw": "Event: 'readable'", "type": "event", "name": "readable", "desc": "When a chunk of data can be read from the stream, it will emit a\n'readable'
event.\n\n
In some cases, listening for a 'readable'
event will cause some data\nto be read into the internal buffer from the underlying system, if it\nhadn't already.\n\n
var readable = getReadableStreamSomehow();\nreadable.on('readable', () => {\n // there is some data to read now\n});
\nOnce the internal buffer is drained, a 'readable'
event will fire\nagain when more data is available.\n\n
The 'readable'
event is not emitted in the "flowing" mode with the\nsole exception of the last one, on end-of-stream.\n\n
The 'readable'
event indicates that the stream has new information:\neither new data is available or the end of the stream has been reached.\nIn the former case, [stream.read()
][stream-read] will return that data. In the\nlatter case, [stream.read()
][stream-read] will return null. For instance, in\nthe following example, foo.txt
is an empty file:\n\n
const fs = require('fs');\nvar rr = fs.createReadStream('foo.txt');\nrr.on('readable', () => {\n console.log('readable:', rr.read());\n});\nrr.on('end', () => {\n console.log('end');\n});
\nThe output of running this script is:\n\n
\n$ node test.js\nreadable: null\nend
\n",
"params": []
}
],
"methods": [
{
"textRaw": "readable.isPaused()",
"type": "method",
"name": "isPaused",
"signatures": [
{
"return": {
"textRaw": "Return: {Boolean} ",
"name": "return",
"type": "Boolean"
},
"params": []
},
{
"params": []
}
],
"desc": "This method returns whether or not the readable
has been explicitly\npaused by client code (using [stream.pause()
][stream-pause] without a\ncorresponding [stream.resume()
][stream-resume]).\n\n
var readable = new stream.Readable\n\nreadable.isPaused() // === false\nreadable.pause()\nreadable.isPaused() // === true\nreadable.resume()\nreadable.isPaused() // === false
\n"
},
{
"textRaw": "readable.pause()",
"type": "method",
"name": "pause",
"signatures": [
{
"return": {
"textRaw": "Return: `this` ",
"name": "return",
"desc": "`this`"
},
"params": []
},
{
"params": []
}
],
"desc": "This method will cause a stream in flowing mode to stop emitting\n['data'
][] events, switching out of flowing mode. Any data that becomes\navailable will remain in the internal buffer.\n\n
var readable = getReadableStreamSomehow();\nreadable.on('data', (chunk) => {\n console.log('got %d bytes of data', chunk.length);\n readable.pause();\n console.log('there will be no more data for 1 second');\n setTimeout(() => {\n console.log('now data will start flowing again');\n readable.resume();\n }, 1000);\n});
\n"
},
{
"textRaw": "readable.pipe(destination[, options])",
"type": "method",
"name": "pipe",
"signatures": [
{
"params": [
{
"textRaw": "`destination` {stream.Writable} The destination for writing data ",
"name": "destination",
"type": "stream.Writable",
"desc": "The destination for writing data"
},
{
"textRaw": "`options` {Object} Pipe options ",
"options": [
{
"textRaw": "`end` {Boolean} End the writer when the reader ends. Default = `true` ",
"name": "end",
"type": "Boolean",
"desc": "End the writer when the reader ends. Default = `true`"
}
],
"name": "options",
"type": "Object",
"desc": "Pipe options",
"optional": true
}
]
},
{
"params": [
{
"name": "destination"
},
{
"name": "options",
"optional": true
}
]
}
],
"desc": "This method pulls all the data out of a readable stream, and writes it\nto the supplied destination, automatically managing the flow so that\nthe destination is not overwhelmed by a fast readable stream.\n\n
\nMultiple destinations can be piped to safely.\n\n
\nvar readable = getReadableStreamSomehow();\nvar writable = fs.createWriteStream('file.txt');\n// All the data from readable goes into 'file.txt'\nreadable.pipe(writable);
\nThis function returns the destination stream, so you can set up pipe\nchains like so:\n\n
\nvar r = fs.createReadStream('file.txt');\nvar z = zlib.createGzip();\nvar w = fs.createWriteStream('file.txt.gz');\nr.pipe(z).pipe(w);
\nFor example, emulating the Unix cat
command:\n\n
process.stdin.pipe(process.stdout);
\nBy default [stream.end()
][stream-end] is called on the destination when the\nsource stream emits ['end'
][], so that destination
is no longer writable.\nPass { end: false }
as options
to keep the destination stream open.\n\n
This keeps writer
open so that "Goodbye" can be written at the\nend.\n\n
reader.pipe(writer, { end: false });\nreader.on('end', () => {\n writer.end('Goodbye\\n');\n});
\nNote that [process.stderr
][] and [process.stdout
][] are never closed until\nthe process exits, regardless of the specified options.\n\n
The read()
method pulls some data out of the internal buffer and\nreturns it. If there is no data available, then it will return\nnull
.\n\n
If you pass in a size
argument, then it will return that many\nbytes. If size
bytes are not available, then it will return null
,\nunless we've ended, in which case it will return the data remaining\nin the buffer.\n\n
If you do not specify a size
argument, then it will return all the\ndata in the internal buffer.\n\n
This method should only be called in paused mode. In flowing mode,\nthis method is called automatically until the internal buffer is\ndrained.\n\n
\nvar readable = getReadableStreamSomehow();\nreadable.on('readable', () => {\n var chunk;\n while (null !== (chunk = readable.read())) {\n console.log('got %d bytes of data', chunk.length);\n }\n});
\nIf this method returns a data chunk, then it will also trigger the\nemission of a ['data'
][] event.\n\n
Note that calling [stream.read([size])
][stream-read] after the ['end'
][]\nevent has been triggered will return null
. No runtime error will be raised.\n\n
This method will cause the readable stream to resume emitting ['data'
][]\nevents.\n\n
This method will switch the stream into flowing mode. If you do not\nwant to consume the data from a stream, but you do want to get to\nits ['end'
][] event, you can call [stream.resume()
][stream-resume] to open\nthe flow of data.\n\n
var readable = getReadableStreamSomehow();\nreadable.resume();\nreadable.on('end', () => {\n console.log('got to the end, but did not read anything');\n});
\n"
},
{
"textRaw": "readable.setEncoding(encoding)",
"type": "method",
"name": "setEncoding",
"signatures": [
{
"return": {
"textRaw": "Return: `this` ",
"name": "return",
"desc": "`this`"
},
"params": [
{
"textRaw": "`encoding` {String} The encoding to use. ",
"name": "encoding",
"type": "String",
"desc": "The encoding to use."
}
]
},
{
"params": [
{
"name": "encoding"
}
]
}
],
"desc": "Call this function to cause the stream to return strings of the specified\nencoding instead of Buffer objects. For example, if you do\nreadable.setEncoding('utf8')
, then the output data will be interpreted as\nUTF-8 data, and returned as strings. If you do readable.setEncoding('hex')
,\nthen the data will be encoded in hexadecimal string format.\n\n
This properly handles multi-byte characters that would otherwise be\npotentially mangled if you simply pulled the Buffers directly and\ncalled [buf.toString(encoding)
][] on them. If you want to read the data\nas strings, always use this method.\n\n
Also you can disable any encoding at all with readable.setEncoding(null)
.\nThis approach is very useful if you deal with binary data or with large\nmulti-byte strings spread out over multiple chunks.\n\n
var readable = getReadableStreamSomehow();\nreadable.setEncoding('utf8');\nreadable.on('data', (chunk) => {\n assert.equal(typeof chunk, 'string');\n console.log('got %d characters of string data', chunk.length);\n});
\n"
},
{
"textRaw": "readable.unpipe([destination])",
"type": "method",
"name": "unpipe",
"signatures": [
{
"params": [
{
"textRaw": "`destination` {stream.Writable} Optional specific stream to unpipe ",
"name": "destination",
"type": "stream.Writable",
"desc": "Optional specific stream to unpipe",
"optional": true
}
]
},
{
"params": [
{
"name": "destination",
"optional": true
}
]
}
],
"desc": "This method will remove the hooks set up for a previous [stream.pipe()
][]\ncall.\n\n
If the destination is not specified, then all pipes are removed.\n\n
\nIf the destination is specified, but no pipe is set up for it, then\nthis is a no-op.\n\n
\nvar readable = getReadableStreamSomehow();\nvar writable = fs.createWriteStream('file.txt');\n// All the data from readable goes into 'file.txt',\n// but only for the first second\nreadable.pipe(writable);\nsetTimeout(() => {\n console.log('stop writing to file.txt');\n readable.unpipe(writable);\n console.log('manually close the file stream');\n writable.end();\n}, 1000);
\n"
},
{
"textRaw": "readable.unshift(chunk)",
"type": "method",
"name": "unshift",
"signatures": [
{
"params": [
{
"textRaw": "`chunk` {Buffer|String} Chunk of data to unshift onto the read queue ",
"name": "chunk",
"type": "Buffer|String",
"desc": "Chunk of data to unshift onto the read queue"
}
]
},
{
"params": [
{
"name": "chunk"
}
]
}
],
"desc": "This is useful in certain cases where a stream is being consumed by a\nparser, which needs to "un-consume" some data that it has\noptimistically pulled out of the source, so that the stream can be\npassed on to some other party.\n\n
\nNote that stream.unshift(chunk)
cannot be called after the ['end'
][] event\nhas been triggered; a runtime error will be raised.\n\n
If you find that you must often call stream.unshift(chunk)
in your\nprograms, consider implementing a [Transform][] stream instead. (See [API\nfor Stream Implementors][].)\n\n
// Pull off a header delimited by \\n\\n\n// use unshift() if we get too much\n// Call the callback with (error, header, stream)\nconst StringDecoder = require('string_decoder').StringDecoder;\nfunction parseHeader(stream, callback) {\n stream.on('error', callback);\n stream.on('readable', onReadable);\n var decoder = new StringDecoder('utf8');\n var header = '';\n function onReadable() {\n var chunk;\n while (null !== (chunk = stream.read())) {\n var str = decoder.write(chunk);\n if (str.match(/\\n\\n/)) {\n // found the header boundary\n var split = str.split(/\\n\\n/);\n header += split.shift();\n var remaining = split.join('\\n\\n');\n var buf = Buffer.from(remaining, 'utf8');\n if (buf.length)\n stream.unshift(buf);\n stream.removeListener('error', callback);\n stream.removeListener('readable', onReadable);\n // now the body of the message can be read from the stream.\n callback(null, header, stream);\n } else {\n // still reading the header.\n header += str;\n }\n }\n }\n}
\nNote that, unlike [stream.push(chunk)
][stream-push], stream.unshift(chunk)
\nwill not end the reading process by resetting the internal reading state of the\nstream. This can cause unexpected results if unshift()
is called during a\nread (i.e. from within a [stream._read()
][stream-_read] implementation on a\ncustom stream). Following the call to unshift()
with an immediate\n[stream.push('')
][stream-push] will reset the reading state appropriately,\nhowever it is best to simply avoid calling unshift()
while in the process of\nperforming a read.\n\n
Versions of Node.js prior to v0.10 had streams that did not implement the\nentire Streams API as it is today. (See [Compatibility][] for\nmore information.)\n\n
\nIf you are using an older Node.js library that emits ['data'
][] events and\nhas a [stream.pause()
][stream-pause] method that is advisory only, then you\ncan use the wrap()
method to create a [Readable][] stream that uses the old\nstream as its data source.\n\n
You will very rarely ever need to call this function, but it exists\nas a convenience for interacting with old Node.js programs and libraries.\n\n
\nFor example:\n\n
\nconst OldReader = require('./old-api-module.js').OldReader;\nconst Readable = require('stream').Readable;\nconst oreader = new OldReader;\nconst myReader = new Readable().wrap(oreader);\n\nmyReader.on('readable', () => {\n myReader.read(); // etc.\n});
\n"
}
]
},
{
"textRaw": "Class: stream.Transform",
"type": "class",
"name": "stream.Transform",
"desc": "Transform streams are [Duplex][] streams where the output is in some way\ncomputed from the input. They implement both the [Readable][] and\n[Writable][] interfaces.\n\n
\nExamples of Transform streams include:\n\n
\nThe Writable stream interface is an abstraction for a destination\nthat you are writing data to.\n\n
\nExamples of writable streams include:\n\n
\nprocess.stdout
][], [process.stderr
][]Emitted when the stream and any of its underlying resources (a file descriptor,\nfor example) have been closed. The event indicates that no more events will be\nemitted, and no further computation will occur.\n\n
\nNot all streams will emit the 'close'
event as the 'close'
event is\noptional.\n\n
If a [stream.write(chunk)
][stream-write] call returns false
, then the\n'drain'
event will indicate when it is appropriate to begin writing more data\nto the stream.\n\n
// Write the data to the supplied writable stream one million times.\n// Be attentive to back-pressure.\nfunction writeOneMillionTimes(writer, data, encoding, callback) {\n var i = 1000000;\n write();\n function write() {\n var ok = true;\n do {\n i -= 1;\n if (i === 0) {\n // last time!\n writer.write(data, encoding, callback);\n } else {\n // see if we should continue, or wait\n // don't pass the callback, because we're not done yet.\n ok = writer.write(data, encoding);\n }\n } while (i > 0 && ok);\n if (i > 0) {\n // had to stop early!\n // write some more once it drains\n writer.once('drain', write);\n }\n }\n}
\n",
"params": []
},
{
"textRaw": "Event: 'error'",
"type": "event",
"name": "error",
"params": [],
"desc": "Emitted if there was an error when writing or piping data.\n\n
\n" }, { "textRaw": "Event: 'finish'", "type": "event", "name": "finish", "desc": "When the [stream.end()
][stream-end] method has been called, and all data has\nbeen flushed to the underlying system, this event is emitted.\n\n
var writer = getWritableStreamSomehow();\nfor (var i = 0; i < 100; i ++) {\n writer.write('hello, #${i}!\\n');\n}\nwriter.end('this is the end\\n');\nwriter.on('finish', () => {\n console.error('all writes are now complete.');\n});
\n",
"params": []
},
{
"textRaw": "Event: 'pipe'",
"type": "event",
"name": "pipe",
"params": [],
"desc": "This is emitted whenever the [stream.pipe()
][] method is called on a readable\nstream, adding this writable to its set of destinations.\n\n
var writer = getWritableStreamSomehow();\nvar reader = getReadableStreamSomehow();\nwriter.on('pipe', (src) => {\n console.error('something is piping into the writer');\n assert.equal(src, reader);\n});\nreader.pipe(writer);
\n"
},
{
"textRaw": "Event: 'unpipe'",
"type": "event",
"name": "unpipe",
"params": [],
"desc": "This is emitted whenever the [stream.unpipe()
][] method is called on a\nreadable stream, removing this writable from its set of destinations.\n\n
var writer = getWritableStreamSomehow();\nvar reader = getReadableStreamSomehow();\nwriter.on('unpipe', (src) => {\n console.error('something has stopped piping into the writer');\n assert.equal(src, reader);\n});\nreader.pipe(writer);\nreader.unpipe(writer);
\n"
}
],
"methods": [
{
"textRaw": "writable.cork()",
"type": "method",
"name": "cork",
"desc": "Forces buffering of all writes.\n\n
\nBuffered data will be flushed either at [stream.uncork()
][] or at\n[stream.end()
][stream-end] call.\n\n
Call this method when no more data will be written to the stream. If supplied,\nthe callback is attached as a listener on the ['finish'
][] event.\n\n
Calling [stream.write()
][stream-write] after calling\n[stream.end()
][stream-end] will raise an error.\n\n
// write 'hello, ' and then end with 'world!'\nvar file = fs.createWriteStream('example.txt');\nfile.write('hello, ');\nfile.end('world!');\n// writing more now is not allowed!
\n"
},
{
"textRaw": "writable.setDefaultEncoding(encoding)",
"type": "method",
"name": "setDefaultEncoding",
"signatures": [
{
"return": {
"textRaw": "Return: `this` ",
"name": "return",
"desc": "`this`"
},
"params": [
{
"textRaw": "`encoding` {String} The new default encoding ",
"name": "encoding",
"type": "String",
"desc": "The new default encoding"
}
]
},
{
"params": [
{
"name": "encoding"
}
]
}
],
"desc": "Sets the default encoding for a writable stream.\n\n
\n" }, { "textRaw": "writable.uncork()", "type": "method", "name": "uncork", "desc": "Flush all data, buffered since [stream.cork()
][] call.\n\n
This method writes some data to the underlying system, and calls the\nsupplied callback once the data has been fully handled. If an error\noccurs, the callback may or may not be called with the error as its\nfirst argument. To detect write errors, listen for the 'error'
event.\n\n
The return value indicates if you should continue writing right now.\nIf the data had to be buffered internally, then it will return\nfalse
. Otherwise, it will return true
.\n\n
This return value is strictly advisory. You MAY continue to write,\neven if it returns false
. However, writes will be buffered in\nmemory, so it is best not to do this excessively. Instead, wait for\nthe ['drain'
][] event before writing more data.\n\n\n
To implement any sort of stream, the pattern is the same:\n\n
\nutil.inherits()
][] method is particularly helpful for this.)The class to extend and the method(s) to implement depend on the sort\nof stream class you are writing:\n\n
\n\n Use-case \n | \n \n Class \n | \n \n Method(s) to implement \n | \n
---|---|---|
\n Reading only \n | \n \n \n | \n\n
| \n
\n Writing only \n | \n \n \n | \n\n
| \n
\n Reading and writing \n | \n \n \n | \n\n
| \n
\n Operate on written data, then read the result \n | \n \n \n | \n\n
| \n
In your implementation code, it is very important to never call the methods\ndescribed in [API for Stream Consumers][]. Otherwise, you can potentially cause\nadverse side effects in programs that consume your streaming interfaces.\n\n
\n", "classes": [ { "textRaw": "Class: stream.Duplex", "type": "class", "name": "stream.Duplex", "desc": "A "duplex" stream is one that is both Readable and Writable, such as a TCP\nsocket connection.\n\n
\nNote that stream.Duplex
is an abstract class designed to be extended\nwith an underlying implementation of the [stream._read(size)
][stream-_read]\nand [stream._write(chunk, encoding, callback)
][stream-_write] methods as you\nwould with a Readable or Writable stream class.\n\n
Since JavaScript doesn't have multiple prototypal inheritance, this class\nprototypally inherits from Readable, and then parasitically from Writable. It is\nthus up to the user to implement both the low-level\n[stream._read(n)
][stream-_read] method as well as the low-level\n[stream._write(chunk, encoding, callback)
][stream-_write] method on extension\nduplex classes.\n\n
In classes that extend the Duplex class, make sure to call the\nconstructor so that the buffering settings can be properly\ninitialized.\n\n
\n" } ] }, { "textRaw": "Class: stream.PassThrough", "type": "class", "name": "stream.PassThrough", "desc": "This is a trivial implementation of a [Transform][] stream that simply\npasses the input bytes across to the output. Its purpose is mainly\nfor examples and testing, but there are occasionally use cases where\nit can come in handy as a building block for novel sorts of streams.\n\n
\n" }, { "textRaw": "Class: stream.Readable", "type": "class", "name": "stream.Readable", "desc": "stream.Readable
is an abstract class designed to be extended with an\nunderlying implementation of the [stream._read(size)
][stream-_read] method.\n\n
Please see [API for Stream Consumers][] for how to consume\nstreams in your programs. What follows is an explanation of how to\nimplement Readable streams in your programs.\n\n
\n", "methods": [ { "textRaw": "new stream.Readable([options])", "type": "method", "name": "Readable", "signatures": [ { "params": [ { "textRaw": "`options` {Object} ", "options": [ { "textRaw": "`highWaterMark` {Number} The maximum number of bytes to store in the internal buffer before ceasing to read from the underlying resource. Default = `16384` (16kb), or `16` for `objectMode` streams ", "name": "highWaterMark", "type": "Number", "desc": "The maximum number of bytes to store in the internal buffer before ceasing to read from the underlying resource. Default = `16384` (16kb), or `16` for `objectMode` streams" }, { "textRaw": "`encoding` {String} If specified, then buffers will be decoded to strings using the specified encoding. Default = `null` ", "name": "encoding", "type": "String", "desc": "If specified, then buffers will be decoded to strings using the specified encoding. Default = `null`" }, { "textRaw": "`objectMode` {Boolean} Whether this stream should behave as a stream of objects. Meaning that [`stream.read(n)`][stream-read] returns a single value instead of a Buffer of size n. Default = `false` ", "name": "objectMode", "type": "Boolean", "desc": "Whether this stream should behave as a stream of objects. Meaning that [`stream.read(n)`][stream-read] returns a single value instead of a Buffer of size n. Default = `false`" }, { "textRaw": "`read` {Function} Implementation for the [`stream._read()`][stream-_read] method. ", "name": "read", "type": "Function", "desc": "Implementation for the [`stream._read()`][stream-_read] method." } ], "name": "options", "type": "Object", "optional": true } ] }, { "params": [ { "name": "options", "optional": true } ] } ], "desc": "In classes that extend the Readable class, make sure to call the\nReadable constructor so that the buffering settings can be properly\ninitialized.\n\n
\n" }, { "textRaw": "readable.\\_read(size)", "type": "method", "name": "\\_read", "signatures": [ { "params": [ { "textRaw": "`size` {Number} Number of bytes to read asynchronously ", "name": "size", "type": "Number", "desc": "Number of bytes to read asynchronously" } ] }, { "params": [ { "name": "size" } ] } ], "desc": "Note: Implement this method, but do NOT call it directly.\n\n
\nThis method is prefixed with an underscore because it is internal to the\nclass that defines it and should only be called by the internal Readable\nclass methods. All Readable stream implementations must provide a _read\nmethod to fetch data from the underlying resource.\n\n
\nWhen _read()
is called, if data is available from the resource, the _read()
\nimplementation should start pushing that data into the read queue by calling\n[this.push(dataChunk)
][stream-push]. _read()
should continue reading from\nthe resource and pushing data until push returns false
, at which point it\nshould stop reading from the resource. Only when _read()
is called again after\nit has stopped should it start reading more data from the resource and pushing\nthat data onto the queue.\n\n
Note: once the _read()
method is called, it will not be called again until\nthe [stream.push()
][stream-push] method is called.\n\n
The size
argument is advisory. Implementations where a "read" is a\nsingle call that returns data can use this to know how much data to\nfetch. Implementations where that is not relevant, such as TCP or\nTLS, may ignore this argument, and simply provide data whenever it\nbecomes available. There is no need, for example to "wait" until\nsize
bytes are available before calling [stream.push(chunk)
][stream-push].\n\n
Note: This method should be called by Readable implementors, NOT\nby consumers of Readable streams.\n\n
\nIf a value other than null is passed, The push()
method adds a chunk of data\ninto the queue for subsequent stream processors to consume. If null
is\npassed, it signals the end of the stream (EOF), after which no more data\ncan be written.\n\n
The data added with push()
can be pulled out by calling the\n[stream.read()
][stream-read] method when the ['readable'
][] event fires.\n\n
This API is designed to be as flexible as possible. For example,\nyou may be wrapping a lower-level source which has some sort of\npause/resume mechanism, and a data callback. In those cases, you\ncould wrap the low-level source object by doing something like this:\n\n
\n// source is an object with readStop() and readStart() methods,\n// and an `ondata` member that gets called when it has data, and\n// an `onend` member that gets called when the data is over.\n\nutil.inherits(SourceWrapper, Readable);\n\nfunction SourceWrapper(options) {\n Readable.call(this, options);\n\n this._source = getLowlevelSourceObject();\n\n // Every time there's data, we push it into the internal buffer.\n this._source.ondata = (chunk) => {\n // if push() returns false, then we need to stop reading from source\n if (!this.push(chunk))\n this._source.readStop();\n };\n\n // When the source ends, we push the EOF-signaling `null` chunk\n this._source.onend = () => {\n this.push(null);\n };\n}\n\n// _read will be called when the stream wants to pull more data in\n// the advisory size argument is ignored in this case.\nSourceWrapper.prototype._read = function(size) {\n this._source.readStart();\n};
\nThis is a basic example of a Readable stream. It emits the numerals\nfrom 1 to 1,000,000 in ascending order, and then ends.\n\n
\nconst Readable = require('stream').Readable;\nconst util = require('util');\nutil.inherits(Counter, Readable);\n\nfunction Counter(opt) {\n Readable.call(this, opt);\n this._max = 1000000;\n this._index = 1;\n}\n\nCounter.prototype._read = function() {\n var i = this._index++;\n if (i > this._max)\n this.push(null);\n else {\n var str = '' + i;\n var buf = Buffer.from(str, 'ascii');\n this.push(buf);\n }\n};
\nThis is similar to the parseHeader
function described\nhere, but implemented as a custom stream.\nAlso, note that this implementation does not convert the incoming data to a\nstring.\n\n
However, this would be better implemented as a [Transform][] stream. See\n[SimpleProtocol v2][] for a better implementation.\n\n
\n// A parser for a simple data protocol.\n// The "header" is a JSON object, followed by 2 \\n characters, and\n// then a message body.\n//\n// NOTE: This can be done more simply as a Transform stream!\n// Using Readable directly for this is sub-optimal. See the\n// alternative example below under the Transform section.\n\nconst Readable = require('stream').Readable;\nconst util = require('util');\n\nutil.inherits(SimpleProtocol, Readable);\n\nfunction SimpleProtocol(source, options) {\n if (!(this instanceof SimpleProtocol))\n return new SimpleProtocol(source, options);\n\n Readable.call(this, options);\n this._inBody = false;\n this._sawFirstCr = false;\n\n // source is a readable stream, such as a socket or file\n this._source = source;\n\n source.on('end', () => {\n this.push(null);\n });\n\n // give it a kick whenever the source is readable\n // read(0) will not consume any bytes\n source.on('readable', () => {\n this.read(0);\n });\n\n this._rawHeader = [];\n this.header = null;\n}\n\nSimpleProtocol.prototype._read = function(n) {\n if (!this._inBody) {\n var chunk = this._source.read();\n\n // if the source doesn't have data, we don't have data yet.\n if (chunk === null)\n return this.push('');\n\n // check if the chunk has a \\n\\n\n var split = -1;\n for (var i = 0; i < chunk.length; i++) {\n if (chunk[i] === 10) { // '\\n'\n if (this._sawFirstCr) {\n split = i;\n break;\n } else {\n this._sawFirstCr = true;\n }\n } else {\n this._sawFirstCr = false;\n }\n }\n\n if (split === -1) {\n // still waiting for the \\n\\n\n // stash the chunk, and try again.\n this._rawHeader.push(chunk);\n this.push('');\n } else {\n this._inBody = true;\n var h = chunk.slice(0, split);\n this._rawHeader.push(h);\n var header = Buffer.concat(this._rawHeader).toString();\n try {\n this.header = JSON.parse(header);\n } catch (er) {\n this.emit('error', new Error('invalid simple protocol data'));\n return;\n }\n // now, because we got some extra data, unshift the rest\n // back into the read queue so that our consumer will see it.\n var b = chunk.slice(split);\n this.unshift(b);\n // calling unshift by itself does not reset the reading state\n // of the stream; since we're inside _read, doing an additional\n // push('') will reset the state appropriately.\n this.push('');\n\n // and let them know that we are done parsing the header.\n this.emit('header', this.header);\n }\n } else {\n // from there on, just provide the data to our consumer.\n // careful not to push(null), since that would indicate EOF.\n var chunk = this._source.read();\n if (chunk) this.push(chunk);\n }\n};\n\n// Usage:\n// var parser = new SimpleProtocol(source);\n// Now parser is a readable stream that will emit 'header'\n// with the parsed header data.
\n"
}
]
},
{
"textRaw": "Class: stream.Transform",
"type": "class",
"name": "stream.Transform",
"desc": "A "transform" stream is a duplex stream where the output is causally\nconnected in some way to the input, such as a [zlib][] stream or a\n[crypto][] stream.\n\n
\nThere is no requirement that the output be the same size as the input,\nthe same number of chunks, or arrive at the same time. For example, a\nHash stream will only ever have a single chunk of output which is\nprovided when the input is ended. A zlib stream will produce output\nthat is either much smaller or much larger than its input.\n\n
\nRather than implement the [stream._read()
][stream-_read] and\n[stream._write()
][stream-_write] methods, Transform classes must implement the\n[stream._transform()
][stream-_transform] method, and may optionally\nalso implement the [stream._flush()
][stream-_flush] method. (See below.)\n\n
In classes that extend the Transform class, make sure to call the\nconstructor so that the buffering settings can be properly\ninitialized.\n\n
\n" }, { "textRaw": "transform.\\_flush(callback)", "type": "method", "name": "\\_flush", "signatures": [ { "params": [ { "textRaw": "`callback` {Function} Call this function (optionally with an error argument) when you are done flushing any remaining data. ", "name": "callback", "type": "Function", "desc": "Call this function (optionally with an error argument) when you are done flushing any remaining data." } ] }, { "params": [ { "name": "callback" } ] } ], "desc": "Note: This function MUST NOT be called directly. It MAY be implemented\nby child classes, and if so, will be called by the internal Transform\nclass methods only.\n\n
\nIn some cases, your transform operation may need to emit a bit more\ndata at the end of the stream. For example, a Zlib
compression\nstream will store up some internal state so that it can optimally\ncompress the output. At the end, however, it needs to do the best it\ncan with what is left, so that the data will be complete.\n\n
In those cases, you can implement a _flush()
method, which will be\ncalled at the very end, after all the written data is consumed, but\nbefore emitting ['end'
][] to signal the end of the readable side. Just\nlike with [stream._transform()
][stream-_transform], call\ntransform.push(chunk)
zero or more times, as appropriate, and call callback
\nwhen the flush operation is complete.\n\n
This method is prefixed with an underscore because it is internal to\nthe class that defines it, and should not be called directly by user\nprograms. However, you are expected to override this method in\nyour own extension classes.\n\n
\n" }, { "textRaw": "transform.\\_transform(chunk, encoding, callback)", "type": "method", "name": "\\_transform", "signatures": [ { "params": [ { "textRaw": "`chunk` {Buffer|String} The chunk to be transformed. Will **always** be a buffer unless the `decodeStrings` option was set to `false`. ", "name": "chunk", "type": "Buffer|String", "desc": "The chunk to be transformed. Will **always** be a buffer unless the `decodeStrings` option was set to `false`." }, { "textRaw": "`encoding` {String} If the chunk is a string, then this is the encoding type. If chunk is a buffer, then this is the special value - 'buffer', ignore it in this case. ", "name": "encoding", "type": "String", "desc": "If the chunk is a string, then this is the encoding type. If chunk is a buffer, then this is the special value - 'buffer', ignore it in this case." }, { "textRaw": "`callback` {Function} Call this function (optionally with an error argument and data) when you are done processing the supplied chunk. ", "name": "callback", "type": "Function", "desc": "Call this function (optionally with an error argument and data) when you are done processing the supplied chunk." } ] }, { "params": [ { "name": "chunk" }, { "name": "encoding" }, { "name": "callback" } ] } ], "desc": "Note: This function MUST NOT be called directly. It should be\nimplemented by child classes, and called by the internal Transform\nclass methods only.\n\n
\nAll Transform stream implementations must provide a _transform()
\nmethod to accept input and produce output.\n\n
_transform()
should do whatever has to be done in this specific\nTransform class, to handle the bytes being written, and pass them off\nto the readable portion of the interface. Do asynchronous I/O,\nprocess things, and so on.\n\n
Call transform.push(outputChunk)
0 or more times to generate output\nfrom this input chunk, depending on how much data you want to output\nas a result of this chunk.\n\n
Call the callback function only when the current chunk is completely\nconsumed. Note that there may or may not be output as a result of any\nparticular input chunk. If you supply a second argument to the callback\nit will be passed to the push method. In other words the following are\nequivalent:\n\n
\ntransform.prototype._transform = function (data, encoding, callback) {\n this.push(data);\n callback();\n};\n\ntransform.prototype._transform = function (data, encoding, callback) {\n callback(null, data);\n};
\nThis method is prefixed with an underscore because it is internal to\nthe class that defines it, and should not be called directly by user\nprograms. However, you are expected to override this method in\nyour own extension classes.\n\n
\nSimpleProtocol
parser v2The example here of a simple\nprotocol parser can be implemented simply by using the higher level\n[Transform][] stream class, similar to the parseHeader
and SimpleProtocol\nv1
examples.\n\n
In this example, rather than providing the input as an argument, it\nwould be piped into the parser, which is a more idiomatic Node.js stream\napproach.\n\n
\nconst util = require('util');\nconst Transform = require('stream').Transform;\nutil.inherits(SimpleProtocol, Transform);\n\nfunction SimpleProtocol(options) {\n if (!(this instanceof SimpleProtocol))\n return new SimpleProtocol(options);\n\n Transform.call(this, options);\n this._inBody = false;\n this._sawFirstCr = false;\n this._rawHeader = [];\n this.header = null;\n}\n\nSimpleProtocol.prototype._transform = function(chunk, encoding, done) {\n if (!this._inBody) {\n // check if the chunk has a \\n\\n\n var split = -1;\n for (var i = 0; i < chunk.length; i++) {\n if (chunk[i] === 10) { // '\\n'\n if (this._sawFirstCr) {\n split = i;\n break;\n } else {\n this._sawFirstCr = true;\n }\n } else {\n this._sawFirstCr = false;\n }\n }\n\n if (split === -1) {\n // still waiting for the \\n\\n\n // stash the chunk, and try again.\n this._rawHeader.push(chunk);\n } else {\n this._inBody = true;\n var h = chunk.slice(0, split);\n this._rawHeader.push(h);\n var header = Buffer.concat(this._rawHeader).toString();\n try {\n this.header = JSON.parse(header);\n } catch (er) {\n this.emit('error', new Error('invalid simple protocol data'));\n return;\n }\n // and let them know that we are done parsing the header.\n this.emit('header', this.header);\n\n // now, because we got some extra data, emit this first.\n this.push(chunk.slice(split));\n }\n } else {\n // from there on, just provide the data to our consumer as-is.\n this.push(chunk);\n }\n done();\n};\n\n// Usage:\n// var parser = new SimpleProtocol();\n// source.pipe(parser)\n// Now parser is a readable stream that will emit 'header'\n// with the parsed header data.
\n"
}
],
"modules": [
{
"textRaw": "Events: 'finish' and 'end'",
"name": "events:_'finish'_and_'end'",
"desc": "The ['finish'
][] and ['end'
][] events are from the parent Writable\nand Readable classes respectively. The 'finish'
event is fired after\n[stream.end()
][stream-end] is called and all chunks have been processed by\n[stream._transform()
][stream-_transform], 'end'
is fired after all data has\nbeen output which is after the callback in [stream._flush()
][stream-_flush]\nhas been called.\n\n
stream.Writable
is an abstract class designed to be extended with an\nunderlying implementation of the\n[stream._write(chunk, encoding, callback)
][stream-_write] method.\n\n
Please see [API for Stream Consumers][] for how to consume\nwritable streams in your programs. What follows is an explanation of\nhow to implement Writable streams in your programs.\n\n
\n", "methods": [ { "textRaw": "new stream.Writable([options])", "type": "method", "name": "Writable", "signatures": [ { "params": [ { "textRaw": "`options` {Object} ", "options": [ { "textRaw": "`highWaterMark` {Number} Buffer level when [`stream.write()`][stream-write] starts returning `false`. Default = `16384` (16kb), or `16` for `objectMode` streams. ", "name": "highWaterMark", "type": "Number", "desc": "Buffer level when [`stream.write()`][stream-write] starts returning `false`. Default = `16384` (16kb), or `16` for `objectMode` streams." }, { "textRaw": "`decodeStrings` {Boolean} Whether or not to decode strings into Buffers before passing them to [`stream._write()`][stream-_write]. Default = `true` ", "name": "decodeStrings", "type": "Boolean", "desc": "Whether or not to decode strings into Buffers before passing them to [`stream._write()`][stream-_write]. Default = `true`" }, { "textRaw": "`objectMode` {Boolean} Whether or not the [`stream.write(anyObj)`][stream-write] is a valid operation. If set you can write arbitrary data instead of only `Buffer` / `String` data. Default = `false` ", "name": "objectMode", "type": "Boolean", "desc": "Whether or not the [`stream.write(anyObj)`][stream-write] is a valid operation. If set you can write arbitrary data instead of only `Buffer` / `String` data. Default = `false`" }, { "textRaw": "`write` {Function} Implementation for the [`stream._write()`][stream-_write] method. ", "name": "write", "type": "Function", "desc": "Implementation for the [`stream._write()`][stream-_write] method." }, { "textRaw": "`writev` {Function} Implementation for the [`stream._writev()`][stream-_writev] method. ", "name": "writev", "type": "Function", "desc": "Implementation for the [`stream._writev()`][stream-_writev] method." } ], "name": "options", "type": "Object", "optional": true } ] }, { "params": [ { "name": "options", "optional": true } ] } ], "desc": "In classes that extend the Writable class, make sure to call the\nconstructor so that the buffering settings can be properly\ninitialized.\n\n
\n" }, { "textRaw": "writable.\\_write(chunk, encoding, callback)", "type": "method", "name": "\\_write", "signatures": [ { "params": [ { "textRaw": "`chunk` {Buffer|String} The chunk to be written. Will **always** be a buffer unless the `decodeStrings` option was set to `false`. ", "name": "chunk", "type": "Buffer|String", "desc": "The chunk to be written. Will **always** be a buffer unless the `decodeStrings` option was set to `false`." }, { "textRaw": "`encoding` {String} If the chunk is a string, then this is the encoding type. If chunk is a buffer, then this is the special value - 'buffer', ignore it in this case. ", "name": "encoding", "type": "String", "desc": "If the chunk is a string, then this is the encoding type. If chunk is a buffer, then this is the special value - 'buffer', ignore it in this case." }, { "textRaw": "`callback` {Function} Call this function (optionally with an error argument) when you are done processing the supplied chunk. ", "name": "callback", "type": "Function", "desc": "Call this function (optionally with an error argument) when you are done processing the supplied chunk." } ] }, { "params": [ { "name": "chunk" }, { "name": "encoding" }, { "name": "callback" } ] } ], "desc": "All Writable stream implementations must provide a\n[stream._write()
][stream-_write] method to send data to the underlying\nresource.\n\n
Note: This function MUST NOT be called directly. It should be\nimplemented by child classes, and called by the internal Writable\nclass methods only.\n\n
\nCall the callback using the standard callback(error)
pattern to\nsignal that the write completed successfully or with an error.\n\n
If the decodeStrings
flag is set in the constructor options, then\nchunk
may be a string rather than a Buffer, and encoding
will\nindicate the sort of string that it is. This is to support\nimplementations that have an optimized handling for certain string\ndata encodings. If you do not explicitly set the decodeStrings
\noption to false
, then you can safely ignore the encoding
argument,\nand assume that chunk
will always be a Buffer.\n\n
This method is prefixed with an underscore because it is internal to\nthe class that defines it, and should not be called directly by user\nprograms. However, you are expected to override this method in\nyour own extension classes.\n\n
\n" }, { "textRaw": "writable.\\_writev(chunks, callback)", "type": "method", "name": "\\_writev", "signatures": [ { "params": [ { "textRaw": "`chunks` {Array} The chunks to be written. Each chunk has following format: `{ chunk: ..., encoding: ... }`. ", "name": "chunks", "type": "Array", "desc": "The chunks to be written. Each chunk has following format: `{ chunk: ..., encoding: ... }`." }, { "textRaw": "`callback` {Function} Call this function (optionally with an error argument) when you are done processing the supplied chunks. ", "name": "callback", "type": "Function", "desc": "Call this function (optionally with an error argument) when you are done processing the supplied chunks." } ] }, { "params": [ { "name": "chunks" }, { "name": "callback" } ] } ], "desc": "Note: This function MUST NOT be called directly. It may be\nimplemented by child classes, and called by the internal Writable\nclass methods only.\n\n
\nThis function is completely optional to implement. In most cases it is\nunnecessary. If implemented, it will be called with all the chunks\nthat are buffered in the write queue.\n\n\n
\n" } ] } ] }, { "textRaw": "Simplified Constructor API", "name": "Simplified Constructor API", "type": "misc", "desc": "In simple cases there is now the added benefit of being able to construct a\nstream without inheritance.\n\n
\nThis can be done by passing the appropriate methods as constructor options:\n\n
\nExamples:\n\n
\n", "miscs": [ { "textRaw": "Duplex", "name": "duplex", "desc": "var duplex = new stream.Duplex({\n read: function(n) {\n // sets this._read under the hood\n\n // push data onto the read queue, passing null\n // will signal the end of the stream (EOF)\n this.push(chunk);\n },\n write: function(chunk, encoding, next) {\n // sets this._write under the hood\n\n // An optional error can be passed as the first argument\n next()\n }\n});\n\n// or\n\nvar duplex = new stream.Duplex({\n read: function(n) {\n // sets this._read under the hood\n\n // push data onto the read queue, passing null\n // will signal the end of the stream (EOF)\n this.push(chunk);\n },\n writev: function(chunks, next) {\n // sets this._writev under the hood\n\n // An optional error can be passed as the first argument\n next()\n }\n});
\n",
"type": "misc",
"displayName": "Duplex"
},
{
"textRaw": "Readable",
"name": "readable",
"desc": "var readable = new stream.Readable({\n read: function(n) {\n // sets this._read under the hood\n\n // push data onto the read queue, passing null\n // will signal the end of the stream (EOF)\n this.push(chunk);\n }\n});
\n",
"type": "misc",
"displayName": "Readable"
},
{
"textRaw": "Transform",
"name": "transform",
"desc": "var transform = new stream.Transform({\n transform: function(chunk, encoding, next) {\n // sets this._transform under the hood\n\n // generate output as many times as needed\n // this.push(chunk);\n\n // call when the current chunk is consumed\n next();\n },\n flush: function(done) {\n // sets this._flush under the hood\n\n // generate output as many times as needed\n // this.push(chunk);\n\n done();\n }\n});
\n",
"type": "misc",
"displayName": "Transform"
},
{
"textRaw": "Writable",
"name": "writable",
"desc": "var writable = new stream.Writable({\n write: function(chunk, encoding, next) {\n // sets this._write under the hood\n\n // An optional error can be passed as the first argument\n next()\n }\n});\n\n// or\n\nvar writable = new stream.Writable({\n writev: function(chunks, next) {\n // sets this._writev under the hood\n\n // An optional error can be passed as the first argument\n next()\n }\n});
\n",
"type": "misc",
"displayName": "Writable"
}
]
},
{
"textRaw": "Streams: Under the Hood",
"name": "Streams: Under the Hood",
"type": "misc",
"miscs": [
{
"textRaw": "Buffering",
"name": "Buffering",
"type": "misc",
"desc": "Both Writable and Readable streams will buffer data on an internal\nobject which can be retrieved from _writableState.getBuffer()
or\n_readableState.buffer
, respectively.\n\n
The amount of data that will potentially be buffered depends on the\nhighWaterMark
option which is passed into the constructor.\n\n
Buffering in Readable streams happens when the implementation calls\n[stream.push(chunk)
][stream-push]. If the consumer of the Stream does not\ncall [stream.read()
][stream-read], then the data will sit in the internal\nqueue until it is consumed.\n\n
Buffering in Writable streams happens when the user calls\n[stream.write(chunk)
][stream-write] repeatedly, even when it returns false
.\n\n
The purpose of streams, especially with the [stream.pipe()
][] method, is to\nlimit the buffering of data to acceptable levels, so that sources and\ndestinations of varying speed will not overwhelm the available memory.\n\n
In versions of Node.js prior to v0.10, the Readable stream interface was\nsimpler, but also less powerful and less useful.\n\n
\nstream.read()
][stream-read] method,\n['data'
][] events would start emitting immediately. If you needed to do\nsome I/O to decide how to handle data, then you had to store the chunks\nin some kind of buffer so that they would not be lost.stream.pause()
][stream-pause] method was advisory, rather than\nguaranteed. This meant that you still had to be prepared to receive\n['data'
][] events even when the stream was in a paused state.In Node.js v0.10, the [Readable][] class was added.\nFor backwards compatibility with older Node.js programs, Readable streams\nswitch into "flowing mode" when a ['data'
][] event handler is added, or\nwhen the [stream.resume()
][stream-resume] method is called. The effect is\nthat, even if you are not using the new [stream.read()
][stream-read] method\nand ['readable'
][] event, you no longer have to worry about losing\n['data'
][] chunks.\n\n
Most programs will continue to function normally. However, this\nintroduces an edge case in the following conditions:\n\n
\n'data'
][] event handler is added.stream.resume()
][stream-resume] method is never called.For example, consider the following code:\n\n
\n// WARNING! BROKEN!\nnet.createServer((socket) => {\n\n // we add an 'end' method, but never consume the data\n socket.on('end', () => {\n // It will never get here.\n socket.end('I got your message (but didnt read it)\\n');\n });\n\n}).listen(1337);
\nIn versions of Node.js prior to v0.10, the incoming message data would be\nsimply discarded. However, in Node.js v0.10 and beyond,\nthe socket will remain paused forever.\n\n
\nThe workaround in this situation is to call the\n[stream.resume()
][stream-resume] method to start the flow of data:\n\n
// Workaround\nnet.createServer((socket) => {\n\n socket.on('end', () => {\n socket.end('I got your message (but didnt read it)\\n');\n });\n\n // start the flow of data, discarding it.\n socket.resume();\n\n}).listen(1337);
\nIn addition to new Readable streams switching into flowing mode,\npre-v0.10 style streams can be wrapped in a Readable class using the\n[stream.wrap()
][] method.\n\n\n
Normally, Streams operate on Strings and Buffers exclusively.\n\n
\nStreams that are in object mode can emit generic JavaScript values\nother than Buffers and Strings.\n\n
\nA Readable stream in object mode will always return a single item from\na call to [stream.read(size)
][stream-read], regardless of what the size\nargument is.\n\n
A Writable stream in object mode will always ignore the encoding
\nargument to [stream.write(data, encoding)
][stream-write].\n\n
The special value null
still retains its special value for object\nmode streams. That is, for object mode readable streams, null
as a\nreturn value from [stream.read()
][stream-read] indicates that there is no more\ndata, and [stream.push(null)
][stream-push] will signal the end of stream data\n(EOF
).\n\n
No streams in Node.js core are object mode streams. This pattern is only\nused by userland streaming libraries.\n\n
\nYou should set objectMode
in your stream child class constructor on\nthe options object. Setting objectMode
mid-stream is not safe.\n\n
For Duplex streams objectMode
can be set exclusively for readable or\nwritable side with readableObjectMode
and writableObjectMode
\nrespectively. These options can be used to implement parsers and\nserializers with Transform streams.\n\n
const util = require('util');\nconst StringDecoder = require('string_decoder').StringDecoder;\nconst Transform = require('stream').Transform;\nutil.inherits(JSONParseStream, Transform);\n\n// Gets \\n-delimited JSON string data, and emits the parsed objects\nfunction JSONParseStream() {\n if (!(this instanceof JSONParseStream))\n return new JSONParseStream();\n\n Transform.call(this, { readableObjectMode : true });\n\n this._buffer = '';\n this._decoder = new StringDecoder('utf8');\n}\n\nJSONParseStream.prototype._transform = function(chunk, encoding, cb) {\n this._buffer += this._decoder.write(chunk);\n // split on newlines\n var lines = this._buffer.split(/\\r?\\n/);\n // keep the last partial line buffered\n this._buffer = lines.pop();\n for (var l = 0; l < lines.length; l++) {\n var line = lines[l];\n try {\n var obj = JSON.parse(line);\n } catch (er) {\n this.emit('error', er);\n return;\n }\n // push the parsed object out to the readable consumer\n this.push(obj);\n }\n cb();\n};\n\nJSONParseStream.prototype._flush = function(cb) {\n // Just handle any leftover\n var rem = this._buffer.trim();\n if (rem) {\n try {\n var obj = JSON.parse(rem);\n } catch (er) {\n this.emit('error', er);\n return;\n }\n // push the parsed object out to the readable consumer\n this.push(obj);\n }\n cb();\n};
\n"
},
{
"textRaw": "`stream.read(0)`",
"name": "`stream.read(0)`",
"desc": "There are some cases where you want to trigger a refresh of the\nunderlying readable stream mechanisms, without actually consuming any\ndata. In that case, you can call stream.read(0)
, which will always\nreturn null.\n\n
If the internal read buffer is below the highWaterMark
, and the\nstream is not currently reading, then calling stream.read(0)
will trigger\na low-level [stream._read()
][stream-_read] call.\n\n
There is almost never a need to do this. However, you will see some\ncases in Node.js's internals where this is done, particularly in the\nReadable stream class internals.\n\n
\n", "type": "misc", "displayName": "`stream.read(0)`" }, { "textRaw": "`stream.push('')`", "name": "`stream.push('')`", "desc": "Pushing a zero-byte string or Buffer (when not in [Object mode][]) has an\ninteresting side effect. Because it is a call to\n[stream.push()
][stream-push], it will end the reading
process. However, it\ndoes not add any data to the readable buffer, so there's nothing for\na user to consume.\n\n
Very rarely, there are cases where you have no data to provide now,\nbut the consumer of your stream (or, perhaps, another bit of your own\ncode) will know when to check again, by calling [stream.read(0)
][stream-read].\nIn those cases, you may call stream.push('')
.\n\n
So far, the only use case for this functionality is in the\n[tls.CryptoStream
][] class, which is deprecated in Node.js/io.js v1.0. If you\nfind that you have to use stream.push('')
, please consider another\napproach, because it almost certainly indicates that something is\nhorribly wrong.\n\n
To use this module, do require('string_decoder')
. StringDecoder decodes a\nbuffer to a string. It is a simple interface to buffer.toString()
but provides\nadditional support for utf8.\n\n
const StringDecoder = require('string_decoder').StringDecoder;\nconst decoder = new StringDecoder('utf8');\n\nconst cent = Buffer.from([0xC2, 0xA2]);\nconsole.log(decoder.write(cent));\n\nconst euro = Buffer.from([0xE2, 0x82, 0xAC]);\nconsole.log(decoder.write(euro));
\n",
"classes": [
{
"textRaw": "Class: StringDecoder",
"type": "class",
"name": "StringDecoder",
"desc": "Accepts a single argument, encoding
which defaults to 'utf8'
.\n\n
Returns any trailing bytes that were left in the buffer.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "decoder.write(buffer)", "type": "method", "name": "write", "desc": "Returns a decoded string.\n\n
\n", "signatures": [ { "params": [ { "name": "buffer" } ] } ] } ] } ], "type": "module", "displayName": "StringDecoder" }, { "textRaw": "Timers", "name": "timers", "stability": 3, "stabilityText": "Locked", "desc": "All of the timer functions are globals. You do not need to require()
\nthis module in order to use them.\n\n
Stops an immediateObject
, as created by [setImmediate
][], from triggering.\n\n
Stops an intervalObject
, as created by [setInterval
][], from triggering.\n\n
Prevents a timeoutObject
, as created by [setTimeout
][], from triggering.\n\n
If a timer was previously unref()
d, then ref()
can be called to explicitly\nrequest the timer hold the program open. If the timer is already ref
d calling\nref
again will have no effect.\n\n
Returns the timer.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "setImmediate(callback[, arg][, ...])", "type": "method", "name": "setImmediate", "desc": "Schedules "immediate" execution of callback
after I/O events'\ncallbacks and before timers set by [setTimeout
][] and [setInterval
][] are\ntriggered. Returns an immediateObject
for possible use with\n[clearImmediate
][]. Additional optional arguments may be passed to the\ncallback.\n\n
Callbacks for immediates are queued in the order in which they were created.\nThe entire callback queue is processed every event loop iteration. If an\nimmediate is queued from inside an executing callback, that immediate won't fire\nuntil the next event loop iteration.\n\n
\nIf callback
is not a function setImmediate()
will throw immediately.\n\n
Schedules repeated execution of callback
every delay
milliseconds.\nReturns a intervalObject
for possible use with [clearInterval
][]. Additional\noptional arguments may be passed to the callback.\n\n
To follow browser behavior, when using delays larger than 2147483647\nmilliseconds (approximately 25 days) or less than 1, Node.js will use 1 as the\ndelay
.\n\n
If callback
is not a function setInterval()
will throw immediately.\n\n
Schedules execution of a one-time callback
after delay
milliseconds.\nReturns a timeoutObject
for possible use with [clearTimeout
][]. Additional\noptional arguments may be passed to the callback.\n\n
The callback will likely not be invoked in precisely delay
milliseconds.\nNode.js makes no guarantees about the exact timing of when callbacks will fire,\nnor of their ordering. The callback will be called as close as possible to the\ntime specified.\n\n
To follow browser behavior, when using delays larger than 2147483647\nmilliseconds (approximately 25 days) or less than 1, the timeout is executed\nimmediately, as if the delay
was set to 1.\n\n
If callback
is not a function setTimeout()
will throw immediately.\n\n
The opaque value returned by [setTimeout
][] and [setInterval
][] also has the\nmethod timer.unref()
which allows the creation of a timer that is active but\nif it is the only item left in the event loop, it won't keep the program\nrunning. If the timer is already unref
d calling unref
again will have no\neffect.\n\n
In the case of [setTimeout
][], unref
creates a separate timer that will\nwakeup the event loop, creating too many of these may adversely effect event\nloop performance -- use wisely.\n\n
Returns the timer.\n\n
\n", "signatures": [ { "params": [] } ] } ], "type": "module", "displayName": "Timers" }, { "textRaw": "TLS (SSL)", "name": "tls_(ssl)", "stability": 2, "stabilityText": "Stable", "desc": "Use require('tls')
to access this module.\n\n
The tls
module uses OpenSSL to provide Transport Layer Security and/or\nSecure Socket Layer: encrypted stream communication.\n\n
TLS/SSL is a public/private key infrastructure. Each client and each\nserver must have a private key. A private key is created like this:\n\n
\nopenssl genrsa -out ryans-key.pem 2048
\nAll servers and some clients need to have a certificate. Certificates are public\nkeys signed by a Certificate Authority or self-signed. The first step to\ngetting a certificate is to create a "Certificate Signing Request" (CSR)\nfile. This is done with:\n\n
\nopenssl req -new -sha256 -key ryans-key.pem -out ryans-csr.pem
\nTo create a self-signed certificate with the CSR, do this:\n\n
\nopenssl x509 -req -in ryans-csr.pem -signkey ryans-key.pem -out ryans-cert.pem
\nAlternatively you can send the CSR to a Certificate Authority for signing.\n\n
\nFor Perfect Forward Secrecy, it is required to generate Diffie-Hellman\nparameters:\n\n
\nopenssl dhparam -outform PEM -out dhparam.pem 2048
\nTo create a .pfx or .p12, do this:\n\n
\nopenssl pkcs12 -export -in agent5-cert.pem -inkey agent5-key.pem \\\n -certfile ca-cert.pem -out agent5.pfx
\nin
: certificateinkey
: private keycertfile
: all CA certs concatenated in one file like\ncat ca1-cert.pem ca2-cert.pem > ca-cert.pem
ALPN (Application-Layer Protocol Negotiation Extension), NPN (Next\nProtocol Negotiation) and, SNI (Server Name Indication) are TLS\nhandshake extensions:\n\n
\nThe TLS protocol lets the client renegotiate certain aspects of the TLS session.\nUnfortunately, session renegotiation requires a disproportionate amount of\nserver-side resources, which makes it a potential vector for denial-of-service\nattacks.\n\n
\nTo mitigate this, renegotiation is limited to three times every 10 minutes. An\nerror is emitted on the [tls.TLSSocket
][] instance when the threshold is\nexceeded. These limits are configurable:\n\n
tls.CLIENT_RENEG_LIMIT
: renegotiation limit, default is 3.
tls.CLIENT_RENEG_WINDOW
: renegotiation window in seconds, default is\n10 minutes.
Do not change the defaults without a full understanding of the implications.\n\n
\nTo test the server, connect to it with openssl s_client -connect address:port
\nand tap R<CR>
(i.e., the letter R
followed by a carriage return) a few\ntimes.\n\n
The term "[Forward Secrecy]" or "Perfect Forward Secrecy" describes a feature of\nkey-agreement (i.e., key-exchange) methods. Practically it means that even if\nthe private key of a server is compromised, communication can only be\ndecrypted by eavesdroppers if they manage to obtain the key-pair specifically\ngenerated for each session.\n\n
\nThis is achieved by randomly generating a key pair for key-agreement on every\nhandshake (in contrast to using the same key for all sessions). Methods\nimplementing this technique, thus offering Perfect Forward Secrecy, are\ncalled "ephemeral".\n\n
\nCurrently two methods are commonly used to achieve Perfect Forward Secrecy (note\nthe character "E" appended to the traditional abbreviations):\n\n
\nEphemeral methods may have some performance drawbacks, because key generation\nis expensive.\n\n
\n" } ], "modules": [ { "textRaw": "Modifying the Default TLS Cipher suite", "name": "modifying_the_default_tls_cipher_suite", "desc": "Node.js is built with a default suite of enabled and disabled TLS ciphers.\nCurrently, the default cipher suite is:\n\n
\nECDHE-RSA-AES128-GCM-SHA256:\nECDHE-ECDSA-AES128-GCM-SHA256:\nECDHE-RSA-AES256-GCM-SHA384:\nECDHE-ECDSA-AES256-GCM-SHA384:\nDHE-RSA-AES128-GCM-SHA256:\nECDHE-RSA-AES128-SHA256:\nDHE-RSA-AES128-SHA256:\nECDHE-RSA-AES256-SHA384:\nDHE-RSA-AES256-SHA384:\nECDHE-RSA-AES256-SHA256:\nDHE-RSA-AES256-SHA256:\nHIGH:\n!aNULL:\n!eNULL:\n!EXPORT:\n!DES:\n!RC4:\n!MD5:\n!PSK:\n!SRP:\n!CAMELLIA
\nThis default can be overriden entirely using the --tls-cipher-list
command\nline switch. For instance, the following makes\nECDHE-RSA-AES128-GCM-SHA256:!RC4
the default TLS cipher suite:\n\n
node --tls-cipher-list="ECDHE-RSA-AES128-GCM-SHA256:!RC4"
\nNote that the default cipher suite included within Node.js has been carefully\nselected to reflect current security best practices and risk mitigation.\nChanging the default cipher suite can have a significant impact on the security\nof an application. The --tls-cipher-list
switch should by used only if\nabsolutely necessary.\n\n
This is an encrypted stream.\n\n
\n", "properties": [ { "textRaw": "cryptoStream.bytesWritten", "name": "bytesWritten", "desc": "A proxy to the underlying socket's bytesWritten accessor, this will return\nthe total bytes written to the socket, including the TLS overhead.\n\n
\n" } ] }, { "textRaw": "Class: SecurePair", "type": "class", "name": "SecurePair", "stability": 0, "stabilityText": "Deprecated: Use [`tls.TLSSocket`][] instead.", "desc": "Returned by tls.createSecurePair.\n\n
\n", "events": [ { "textRaw": "Event: 'secure'", "type": "event", "name": "secure", "desc": "This event is emitted from the SecurePair once the pair has successfully\nestablished a secure connection.\n\n
\nAs with checking for the server secureConnection
\nevent, pair.cleartext.authorized
should be inspected to confirm whether the\ncertificate used is properly authorized.\n\n
This class is a subclass of net.Server
and has the same methods on it.\nInstead of accepting only raw TCP connections, this accepts encrypted\nconnections using TLS or SSL.\n\n
function (exception, tlsSocket) { }
\n\n
When a client connection emits an 'error'
event before a secure connection is\nestablished it will be forwarded here.\n\n
tlsSocket
is the [tls.TLSSocket
][] that the error originated from.\n\n
function (sessionId, sessionData, callback) { }
\n\n
Emitted on creation of a TLS session. May be used to store sessions in external\nstorage. callback
must be invoked eventually, otherwise no data will be\nsent or received from the secure connection.\n\n
NOTE: adding this event listener will only have an effect on connections\nestablished after the addition of the event listener.\n\n
\n", "params": [] }, { "textRaw": "Event: 'OCSPRequest'", "type": "event", "name": "OCSPRequest", "desc": "function (certificate, issuer, callback) { }
\n\n
Emitted when the client sends a certificate status request. The server's\ncurrent certificate can be parsed to obtain the OCSP URL and certificate ID;\nafter obtaining an OCSP response callback(null, resp)
is then invoked, where\nresp
is a Buffer
instance. Both certificate
and issuer
are Buffer
\nDER-representations of the primary and issuer's certificates. They can be used\nto obtain the OCSP certificate ID and OCSP endpoint URL.\n\n
Alternatively, callback(null, null)
may be called, meaning that there was no\nOCSP response.\n\n
Calling callback(err)
will result in a socket.destroy(err)
call.\n\n
Typical flow:\n\n
\n'OCSPRequest'
to it (via status\ninfo extension in ClientHello).'OCSPRequest'
event listener\nif present.certificate
or issuer
and\nperforms an [OCSP request] to the CA.OCSPResponse
from the CA and sends it back to the client\nvia the callback
argumentNOTE: issuer
could be null
if the certificate is self-signed or if the\nissuer is not in the root certificates list. (An issuer may be provided via the\nca
option.)\n\n
NOTE: adding this event listener will only have an effect on connections\nestablished after the addition of the event listener.\n\n
\nNOTE: An npm module like [asn1.js] may be used to parse the certificates.\n\n
\n", "params": [] }, { "textRaw": "Event: 'resumeSession'", "type": "event", "name": "resumeSession", "desc": "function (sessionId, callback) { }
\n\n
Emitted when the client wants to resume the previous TLS session. The event\nlistener may perform a lookup in external storage using the given sessionId
\nand invoke callback(null, sessionData)
once finished. If the session can't be\nresumed (i.e., doesn't exist in storage) one may call callback(null, null)
.\nCalling callback(err)
will terminate incoming connection and destroy the\nsocket.\n\n
NOTE: adding this event listener will only have an effect on connections\nestablished after the addition of the event listener.\n\n
\nHere's an example for using TLS session resumption:\n\n
\nvar tlsSessionStore = {};\nserver.on('newSession', (id, data, cb) => {\n tlsSessionStore[id.toString('hex')] = data;\n cb();\n});\nserver.on('resumeSession', (id, cb) => {\n cb(null, tlsSessionStore[id.toString('hex')] || null);\n});
\n",
"params": []
},
{
"textRaw": "Event: 'secureConnection'",
"type": "event",
"name": "secureConnection",
"desc": "function (tlsSocket) {}
\n\n
This event is emitted after the handshaking process for a new connection has\nsuccessfully completed. The argument is an instance of [tls.TLSSocket
][] and\nhas all the common stream methods and events.\n\n
socket.authorized
is a boolean value which indicates if the\nclient has been verified by one of the supplied certificate authorities for the\nserver. If socket.authorized
is false, then socket.authorizationError
is\nset to describe how authorization failed. Implied but worth mentioning:\ndepending on the settings of the TLS server, unauthorized connections may\nbe accepted.\n\n
socket.npnProtocol
is a string containing the selected NPN protocol\nand socket.alpnProtocol
is a string containing the selected ALPN\nprotocol. When both NPN and ALPN extensions are received, ALPN takes\nprecedence over NPN and the next protocol is selected by ALPN. When\nALPN has no selected protocol, this returns false.\n\n
socket.servername
is a string containing the server name requested with\nSNI.\n\n
Add secure context that will be used if the client request's SNI hostname\nmatches the supplied hostname
(wildcards can be used). context
can contain\nkey
, cert
, ca
or any other properties from\n[tls.createSecureContext()
][] options
argument.\n\n
Returns the bound address, the address family name, and port of the\nserver as reported by the operating system. See [net.Server.address()
][] for\nmore information.\n\n
Stops the server from accepting new connections. This function is\nasynchronous, the server is finally closed when the server emits a 'close'
\nevent. Optionally, you can pass a callback to listen for the 'close'
event.\n\n
Returns a Buffer
instance holding the keys currently used for\nencryption/decryption of the [TLS Session Tickets][]\n\n
Begin accepting connections on the specified port
and hostname
. If the\nhostname
is omitted, the server will accept connections on any IPv6 address\n(::
) when IPv6 is available, or any IPv4 address (0.0.0.0
) otherwise. A\nport value of zero will assign a random port.\n\n
This function is asynchronous. The last parameter callback
will be called\nwhen the server has been bound.\n\n
See net.Server
for more information.\n\n
Updates the keys for encryption/decryption of the [TLS Session Tickets][].\n\n
\nNOTE: the buffer should be 48 bytes long. See ticketKeys
option in\ntls.createServer for\nmore information on how it is used.\n\n
NOTE: the change is effective only for future server connections. Existing\nor currently pending server connections will use the previous keys.\n\n
\n", "signatures": [ { "params": [ { "name": "keys" } ] } ] } ], "properties": [ { "textRaw": "server.connections", "name": "connections", "desc": "The number of concurrent connections on the server.\n\n
\n" }, { "textRaw": "server.maxConnections", "name": "maxConnections", "desc": "Set this property to reject connections when the server's connection count\nexceeds the specified threshold.\n\n\n
\n" } ] }, { "textRaw": "Class: tls.TLSSocket", "type": "class", "name": "tls.TLSSocket", "desc": "This is a wrapped version of [net.Socket
][] that does transparent encryption\nof written data and all required TLS negotiation.\n\n
This instance implements the duplex [Stream][] interface. It has all the\ncommon stream methods and events.\n\n
\nMethods that return TLS connection metadata (e.g.\n[tls.TLSSocket.getPeerCertificate()
][] will only return data while the\nconnection is open.\n\n
Construct a new TLSSocket object from an existing TCP socket.\n\n
\nsocket
is an instance of [net.Socket
][]\n\n
options
is an optional object that might contain following properties:\n\n
secureContext
: An optional TLS context object from\n [tls.createSecureContext()
][]
isServer
: If true
the TLS socket will be instantiated in server-mode.\nDefault: false
server
: An optional [net.Server
][] instance
requestCert
: Optional, see [tls.createServer()
][]
rejectUnauthorized
: Optional, see [tls.createServer()
][]
NPNProtocols
: Optional, see [tls.createServer()
][]
ALPNProtocols
: Optional, see [tls.createServer()
][]
SNICallback
: Optional, see [tls.createServer()
][]
session
: Optional, a Buffer
instance, containing a TLS session
requestOCSP
: Optional, if true
the OCSP status request extension will\nbe added to the client hello and an 'OCSPResponse'
event will be emitted\non the socket before establishing a secure communication
Returns the bound address, the address family name, and port of the\nunderlying socket as reported by the operating system. Returns an\nobject with three properties, e.g.,\n{ port: 12346, family: 'IPv4', address: '127.0.0.1' }
\n\n
Returns an object representing the cipher name and the SSL/TLS protocol version\nthat first defined the cipher.\n\n
\nExample:\n{ name: 'AES256-SHA', version: 'TLSv1/SSLv3' }
\n\n
See SSL_CIPHER_get_name() and SSL_CIPHER_get_version() in\nhttps://www.openssl.org/docs/manmaster/ssl/SSL_CIPHER_get_name.html for more\ninformation.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "tlsSocket.getEphemeralKeyInfo()", "type": "method", "name": "getEphemeralKeyInfo", "desc": "Returns an object representing the type, name, and size of parameter of\nan ephemeral key exchange in [Perfect Forward Secrecy][] on a client\nconnection. It returns an empty object when the key exchange is not\nephemeral. As this is only supported on a client socket, it returns null
\nif called on a server socket. The supported types are 'DH' and 'ECDH'. The\nname
property is only available in 'ECDH'.\n\n
Example:\n\n
\n{ type: 'ECDH', name: 'prime256v1', size: 256 }
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "tlsSocket.getPeerCertificate([ detailed ])",
"type": "method",
"name": "getPeerCertificate",
"desc": "Returns an object representing the peer's certificate. The returned object has\nsome properties corresponding to the fields of the certificate. If the\ndetailed
argument is true
the full chain with the issuer
property will be\nreturned, if false
only the top certificate without the issuer
property.\n\n
Example:\n\n
\n{ subject:\n { C: 'UK',\n ST: 'Acknack Ltd',\n L: 'Rhys Jones',\n O: 'node.js',\n OU: 'Test TLS Certificate',\n CN: 'localhost' },\n issuerInfo:\n { C: 'UK',\n ST: 'Acknack Ltd',\n L: 'Rhys Jones',\n O: 'node.js',\n OU: 'Test TLS Certificate',\n CN: 'localhost' },\n issuer:\n { ... another certificate ... },\n raw: < RAW DER buffer >,\n valid_from: 'Nov 11 09:52:22 2009 GMT',\n valid_to: 'Nov 6 09:52:22 2029 GMT',\n fingerprint: '2A:7A:C2:DD:E5:F9:CC:53:72:35:99:7A:02:5A:71:38:52:EC:8A:DF',\n serialNumber: 'B9B0D332A1AA5635' }
\nIf the peer does not provide a certificate, it returns null
or an empty\nobject.\n\n
Returns a string containing the negotiated SSL/TLS protocol version of the\ncurrent connection. 'unknown'
will be returned for connected sockets that have\nnot completed the handshaking process. null
will be returned for server\nsockets or disconnected client sockets.\n\n
Examples:\n
\n'SSLv3'\n'TLSv1'\n'TLSv1.1'\n'TLSv1.2'\n'unknown'
\nSee https://www.openssl.org/docs/manmaster/ssl/SSL_get_version.html for more\ninformation.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "tlsSocket.getSession()", "type": "method", "name": "getSession", "desc": "Returns the ASN.1 encoded TLS session or undefined
if none was negotiated.\nCould be used to speed up handshake establishment when reconnecting to the\nserver.\n\n
NOTE: Works only with client TLS sockets. Useful only for debugging, for\nsession reuse provide session
option to [tls.connect()
][].\n\n
Returns the TLS session ticket or undefined
if none was negotiated.\n\n
Initiate TLS renegotiation process. The options
object may contain the\nfollowing fields: rejectUnauthorized
, requestCert
. (See [tls.createServer\n()
][] for details.) callback(err)
will be executed with null
as err
,\nonce the renegotiation is successfully completed.\n\n
NOTE: Can be used to request peer's certificate after the secure connection\nhas been established.\n\n
\nANOTHER NOTE: When running as the server, socket will be destroyed\nwith an error after handshakeTimeout
timeout.\n\n
Set maximum TLS fragment size (default and maximum value is: 16384
, minimum\nis: 512
). Returns true
on success, false
otherwise.\n\n
Smaller fragment sizes decrease the buffering latency on the client: larger\nfragments are buffered by the TLS layer until the entire fragment is received\nand its integrity is verified; large fragments can span multiple roundtrips\nand their processing can be delayed due to packet loss or reordering. However,\nsmaller fragments add extra TLS framing bytes and CPU overhead, which may\ndecrease overall server throughput.\n\n\n
\n", "signatures": [ { "params": [ { "name": "size" } ] } ] } ], "events": [ { "textRaw": "Event: 'OCSPResponse'", "type": "event", "name": "OCSPResponse", "desc": "function (response) { }
\n\n
This event will be emitted if the requestOCSP
option was set. response
is a\nBuffer
containing the server's OCSP response.\n\n
Traditionally, the response
is a signed object from the server's CA that\ncontains information about server's certificate revocation status.\n\n
This event is emitted after the handshaking process for a new connection has\nsuccessfully completed. The listener will be called regardless of whether or not\nthe server's certificate has been authorized. It is the user's responsibility to\ntest tlsSocket.authorized
to see if the server certificate was signed by one\nof the specified CAs. If tlsSocket.authorized === false
then the error can be\nfound in tlsSocket.authorizationError
. Also, if either ALPN or NPN was used\ntlsSocket.alpnProtocol
or tlsSocket.npnProtocol
can be checked for the\nnegotiated protocol.\n\n
A boolean that is true
if the peer certificate was signed by one of the\nspecified CAs, otherwise false
.\n\n
The reason why the peer's certificate has not been verified. This property\nbecomes available only when tlsSocket.authorized === false
.\n\n
Static boolean value, always true
. May be used to distinguish TLS sockets\nfrom regular ones.\n\n
The string representation of the local IP address.\n\n
\n" }, { "textRaw": "tlsSocket.localPort", "name": "localPort", "desc": "The numeric representation of the local port.\n\n
\n" }, { "textRaw": "tlsSocket.remoteAddress", "name": "remoteAddress", "desc": "The string representation of the remote IP address. For example,\n'74.125.127.100'
or '2001:4860:a005::68'
.\n\n
The string representation of the remote IP family. 'IPv4'
or 'IPv6'
.\n\n
The numeric representation of the remote port. For example, 443
.\n\n
Creates a new client connection to the given port
and host
(old API) or\noptions.port
and options.host
. (If host
is omitted, it defaults to\nlocalhost
.) options
should be an object which specifies:\n\n
host
: Host the client should connect to.
port
: Port the client should connect to.
socket
: Establish secure connection on a given socket rather than\ncreating a new socket. If this option is specified, host
and port
\nare ignored.
path
: Creates unix socket connection to path. If this option is\nspecified, host
and port
are ignored.
pfx
: A string or Buffer
containing the private key, certificate, and\nCA certs of the client in PFX or PKCS12 format.
key
: A string, Buffer
, array of strings, or array of Buffer
s\ncontaining the private key of the client in PEM format.
passphrase
: A string containing the passphrase for the private key or pfx.
cert
: A string, Buffer
, array of strings, or array of Buffer
s\ncontaining the certificate key of the client in PEM format.
ca
: A string, Buffer
, array of strings, or array of Buffer
s of trusted\ncertificates in PEM format. If this is omitted several well known "root"\nCAs (like VeriSign) will be used. These are used to authorize connections.
ciphers
: A string describing the ciphers to use or exclude, separated by\n:
. Uses the same default cipher suite as [tls.createServer()
][].
rejectUnauthorized
: If true
, the server certificate is verified against\nthe list of supplied CAs. An 'error'
event is emitted if verification\nfails; err.code
contains the OpenSSL error code. Default: true
.
NPNProtocols
: An array of strings or Buffer
s containing supported NPN\nprotocols. Buffer
s should have the following format:\n0x05hello0x05world
, where the first byte is the next protocol name's\nlength. (Passing an array is usually be much simpler: ['hello', 'world']
.)
ALPNProtocols
: An array of strings or Buffer
s containing the\nsupported ALPN protocols. Buffer
s should have following format:\n0x05hello0x05world
, where the first byte is the next protocol\nname's length. (Passing an array is usually be much simpler:\n['hello', 'world']
.)
servername
: Server name for the SNI (Server Name Indication) TLS\nextension.
checkServerIdentity(servername, cert)
: Provide an override for checking\nthe server's hostname against the certificate. Should return an error if\nverification fails. Returns undefined
if passing.
secureProtocol
: The SSL method to use, e.g., SSLv3_method
to force\nSSL version 3. The possible values depend on the version of OpenSSL\ninstalled in the environment and are defined in the constant\n[SSL_METHODS][].
secureContext
: An optional TLS context object from\ntls.createSecureContext( ... )
. It can be used for caching client\ncertificates, keys, and CA certificates.
session
: A Buffer
instance, containing TLS session.
minDHSize
: Minimum size of the DH parameter in bits to accept a TLS\nconnection. When a server offers a DH parameter with a size less\nthan this, the TLS connection is destroyed and an error is thrown. Default:\n1024.
The callback
parameter will be added as a listener for the\n['secureConnect'
][] event.\n\n
tls.connect()
returns a [tls.TLSSocket
][] object.\n\n
Here is an example of a client of echo server as described previously:\n\n
\nconst tls = require('tls');\nconst fs = require('fs');\n\nconst options = {\n // These are necessary only if using the client certificate authentication\n key: fs.readFileSync('client-key.pem'),\n cert: fs.readFileSync('client-cert.pem'),\n\n // This is necessary only if the server uses the self-signed certificate\n ca: [ fs.readFileSync('server-cert.pem') ]\n};\n\nvar socket = tls.connect(8000, options, () => {\n console.log('client connected',\n socket.authorized ? 'authorized' : 'unauthorized');\n process.stdin.pipe(socket);\n process.stdin.resume();\n});\nsocket.setEncoding('utf8');\nsocket.on('data', (data) => {\n console.log(data);\n});\nsocket.on('end', () => {\n server.close();\n});
\nOr\n\n
\nconst tls = require('tls');\nconst fs = require('fs');\n\nconst options = {\n pfx: fs.readFileSync('client.pfx')\n};\n\nvar socket = tls.connect(8000, options, () => {\n console.log('client connected',\n socket.authorized ? 'authorized' : 'unauthorized');\n process.stdin.pipe(socket);\n process.stdin.resume();\n});\nsocket.setEncoding('utf8');\nsocket.on('data', (data) => {\n console.log(data);\n});\nsocket.on('end', () => {\n server.close();\n});
\n",
"signatures": [
{
"params": [
{
"name": "port"
},
{
"name": "host",
"optional": true
},
{
"name": "options",
"optional": true
},
{
"name": "callback",
"optional": true
}
]
},
{
"params": [
{
"name": "options"
},
{
"name": "callback",
"optional": true
}
]
}
]
},
{
"textRaw": "tls.connect(port[, host][, options][, callback])",
"type": "method",
"name": "connect",
"desc": "Creates a new client connection to the given port
and host
(old API) or\noptions.port
and options.host
. (If host
is omitted, it defaults to\nlocalhost
.) options
should be an object which specifies:\n\n
host
: Host the client should connect to.
port
: Port the client should connect to.
socket
: Establish secure connection on a given socket rather than\ncreating a new socket. If this option is specified, host
and port
\nare ignored.
path
: Creates unix socket connection to path. If this option is\nspecified, host
and port
are ignored.
pfx
: A string or Buffer
containing the private key, certificate, and\nCA certs of the client in PFX or PKCS12 format.
key
: A string, Buffer
, array of strings, or array of Buffer
s\ncontaining the private key of the client in PEM format.
passphrase
: A string containing the passphrase for the private key or pfx.
cert
: A string, Buffer
, array of strings, or array of Buffer
s\ncontaining the certificate key of the client in PEM format.
ca
: A string, Buffer
, array of strings, or array of Buffer
s of trusted\ncertificates in PEM format. If this is omitted several well known "root"\nCAs (like VeriSign) will be used. These are used to authorize connections.
ciphers
: A string describing the ciphers to use or exclude, separated by\n:
. Uses the same default cipher suite as [tls.createServer()
][].
rejectUnauthorized
: If true
, the server certificate is verified against\nthe list of supplied CAs. An 'error'
event is emitted if verification\nfails; err.code
contains the OpenSSL error code. Default: true
.
NPNProtocols
: An array of strings or Buffer
s containing supported NPN\nprotocols. Buffer
s should have the following format:\n0x05hello0x05world
, where the first byte is the next protocol name's\nlength. (Passing an array is usually be much simpler: ['hello', 'world']
.)
ALPNProtocols
: An array of strings or Buffer
s containing the\nsupported ALPN protocols. Buffer
s should have following format:\n0x05hello0x05world
, where the first byte is the next protocol\nname's length. (Passing an array is usually be much simpler:\n['hello', 'world']
.)
servername
: Server name for the SNI (Server Name Indication) TLS\nextension.
checkServerIdentity(servername, cert)
: Provide an override for checking\nthe server's hostname against the certificate. Should return an error if\nverification fails. Returns undefined
if passing.
secureProtocol
: The SSL method to use, e.g., SSLv3_method
to force\nSSL version 3. The possible values depend on the version of OpenSSL\ninstalled in the environment and are defined in the constant\n[SSL_METHODS][].
secureContext
: An optional TLS context object from\ntls.createSecureContext( ... )
. It can be used for caching client\ncertificates, keys, and CA certificates.
session
: A Buffer
instance, containing TLS session.
minDHSize
: Minimum size of the DH parameter in bits to accept a TLS\nconnection. When a server offers a DH parameter with a size less\nthan this, the TLS connection is destroyed and an error is thrown. Default:\n1024.
The callback
parameter will be added as a listener for the\n['secureConnect'
][] event.\n\n
tls.connect()
returns a [tls.TLSSocket
][] object.\n\n
Here is an example of a client of echo server as described previously:\n\n
\nconst tls = require('tls');\nconst fs = require('fs');\n\nconst options = {\n // These are necessary only if using the client certificate authentication\n key: fs.readFileSync('client-key.pem'),\n cert: fs.readFileSync('client-cert.pem'),\n\n // This is necessary only if the server uses the self-signed certificate\n ca: [ fs.readFileSync('server-cert.pem') ]\n};\n\nvar socket = tls.connect(8000, options, () => {\n console.log('client connected',\n socket.authorized ? 'authorized' : 'unauthorized');\n process.stdin.pipe(socket);\n process.stdin.resume();\n});\nsocket.setEncoding('utf8');\nsocket.on('data', (data) => {\n console.log(data);\n});\nsocket.on('end', () => {\n server.close();\n});
\nOr\n\n
\nconst tls = require('tls');\nconst fs = require('fs');\n\nconst options = {\n pfx: fs.readFileSync('client.pfx')\n};\n\nvar socket = tls.connect(8000, options, () => {\n console.log('client connected',\n socket.authorized ? 'authorized' : 'unauthorized');\n process.stdin.pipe(socket);\n process.stdin.resume();\n});\nsocket.setEncoding('utf8');\nsocket.on('data', (data) => {\n console.log(data);\n});\nsocket.on('end', () => {\n server.close();\n});
\n",
"signatures": [
{
"params": [
{
"name": "port"
},
{
"name": "host",
"optional": true
},
{
"name": "options",
"optional": true
},
{
"name": "callback",
"optional": true
}
]
}
]
},
{
"textRaw": "tls.createSecureContext(options)",
"type": "method",
"name": "createSecureContext",
"desc": "Creates a credentials object; the options
object may contain the following\nfields:\n\n
pfx
: A string or Buffer
holding the PFX or PKCS12 encoded private\nkey, certificate, and CA certificates.key
: A string or Buffer
containing the private key of the server in\nPEM format. To support multiple keys using different algorithms, an array\ncan be provided. It can either be a plain array of keys or an array of\nobjects in the format {pem: key, passphrase: passphrase}
. (Required)passphrase
: A string containing the passphrase for the private key or pfx.cert
: A string containing the PEM encoded certificateca
: A string, Buffer
, array of strings, or array of Buffer
s of trusted\ncertificates in PEM format. If this is omitted several well known "root"\nCAs (like VeriSign) will be used. These are used to authorize connections.crl
: Either a string or list of strings of PEM encoded CRLs\n(Certificate Revocation List).ciphers
: A string describing the ciphers to use or exclude.\nConsult\nhttps://www.openssl.org/docs/apps/ciphers.html#CIPHER_LIST_FORMAT\nfor details on the format.honorCipherOrder
: When choosing a cipher, use the server's preferences\ninstead of the client preferences. For further details see tls
module\ndocumentation.If no 'CA' details are given, then Node.js will use the default\npublicly trusted list of CAs as given in\n
\nhttp://mxr.mozilla.org/mozilla/source/security/nss/lib/ckfw/builtins/certdata.txt.\n\n
\n", "signatures": [ { "params": [ { "name": "options" } ] } ] }, { "textRaw": "tls.createSecurePair([context][, isServer][, requestCert][, rejectUnauthorized][, options])", "type": "method", "name": "createSecurePair", "stability": 0, "stabilityText": "Deprecated: Use [`tls.TLSSocket`][] instead.", "desc": "Creates a new secure pair object with two streams, one of which reads and writes\nthe encrypted data and the other of which reads and writes the cleartext data.\nGenerally, the encrypted stream is piped to/from an incoming encrypted data\nstream and the cleartext one is used as a replacement for the initial encrypted\nstream.\n\n
\ncredentials
: A secure context object from tls.createSecureContext( ... )
.
isServer
: A boolean indicating whether this TLS connection should be\nopened as a server or a client.
requestCert
: A boolean indicating whether a server should request a\ncertificate from a connecting client. Only applies to server connections.
rejectUnauthorized
: A boolean indicating whether a server should\nautomatically reject clients with invalid certificates. Only applies to\nservers with requestCert
enabled.
options
: An object with common SSL options. See [tls.TLSSocket
][].
tls.createSecurePair()
returns a SecurePair object with cleartext
and\nencrypted
stream properties.\n\n
NOTE: cleartext
has the same API as [tls.TLSSocket
][]\n\n
Deprecated tls.createSecurePair()
is now deprecated in favor of\ntls.TLSSocket()
. For example:\n\n
pair = tls.createSecurePair( ... );\npair.encrypted.pipe(socket);\nsocket.pipe(pair.encrypted);
\ncan be replaced with:\n\n
\nsecure_socket = tls.TLSSocket(socket, options);
\nwhere secure_socket
has the same API as pair.cleartext
.\n\n
Creates a new [tls.Server][]. The connectionListener
argument is\nautomatically set as a listener for the ['secureConnection'
][] event. The\noptions
object may contain the following fields:\n\n
pfx
: A string or Buffer
containing the private key, certificate and\nCA certs of the server in PFX or PKCS12 format. (Mutually exclusive with\nthe key
, cert
, and ca
options.)
key
: A string or Buffer
containing the private key of the server in\nPEM format. To support multiple keys using different algorithms an array\ncan be provided. It can either be a plain array of keys or an array of\nobjects in the format {pem: key, passphrase: passphrase}
. (Required)
passphrase
: A string containing the passphrase for the private key or pfx.
cert
: A string, Buffer
, array of strings, or array of Buffer
s\ncontaining the certificate key of the server in PEM format. (Required)
ca
: A string, Buffer
, array of strings, or array of Buffer
s of trusted\ncertificates in PEM format. If this is omitted several well known "root"\nCAs (like VeriSign) will be used. These are used to authorize connections.
crl
: Either a string or array of strings of PEM encoded CRLs (Certificate\nRevocation List).
ciphers
: A string describing the ciphers to use or exclude, separated by\n:
. The default cipher suite is:
ECDHE-RSA-AES128-GCM-SHA256:\nECDHE-ECDSA-AES128-GCM-SHA256:\nECDHE-RSA-AES256-GCM-SHA384:\nECDHE-ECDSA-AES256-GCM-SHA384:\nDHE-RSA-AES128-GCM-SHA256:\nECDHE-RSA-AES128-SHA256:\nDHE-RSA-AES128-SHA256:\nECDHE-RSA-AES256-SHA384:\nDHE-RSA-AES256-SHA384:\nECDHE-RSA-AES256-SHA256:\nDHE-RSA-AES256-SHA256:\nHIGH:\n!aNULL:\n!eNULL:\n!EXPORT:\n!DES:\n!RC4:\n!MD5:\n!PSK:\n!SRP:\n!CAMELLIA
\nThe default cipher suite prefers GCM ciphers for [Chrome's 'modern\ncryptography' setting] and also prefers ECDHE and DHE ciphers for Perfect\nForward Secrecy, while offering some backward compatibility.
\n128 bit AES is preferred over 192 and 256 bit AES in light of [specific\nattacks affecting larger AES key sizes].
\nOld clients that rely on insecure and deprecated RC4 or DES-based ciphers\n(like Internet Explorer 6) cannot complete the handshaking process with\nthe default configuration. If these clients must be supported, the\n[TLS recommendations] may offer a compatible cipher suite. For more details\non the format, see the [OpenSSL cipher list format documentation].
\necdhCurve
: A string describing a named curve to use for ECDH key agreement\nor false to disable ECDH.
Defaults to prime256v1
(NIST P-256). Use [crypto.getCurves()
][] to\nobtain a list of available curve names. On recent releases,\nopenssl ecparam -list_curves
will also display the name and description of\neach available elliptic curve.
dhparam
: A string or Buffer
containing Diffie Hellman parameters,\nrequired for Perfect Forward Secrecy. Use openssl dhparam
to create it.\nIts key length should be greater than or equal to 1024 bits, otherwise\nit throws an error. It is strongly recommended to use 2048 bits or\nlarger for stronger security. If omitted or invalid, it is silently\ndiscarded and DHE ciphers won't be available.
handshakeTimeout
: Abort the connection if the SSL/TLS handshake does not\nfinish in the specified number of milliseconds. The default is 120 seconds.
A 'clientError'
is emitted on the tls.Server
object whenever a handshake\ntimes out.
honorCipherOrder
: When choosing a cipher, use the server's preferences\ninstead of the client preferences. Default: true
.
requestCert
: If true
the server will request a certificate from\nclients that connect and attempt to verify that certificate. Default:\nfalse
.
rejectUnauthorized
: If true
the server will reject any connection\nwhich is not authorized with the list of supplied CAs. This option only\nhas an effect if requestCert
is true
. Default: false
.
NPNProtocols
: An array or Buffer
of possible NPN protocols. (Protocols\nshould be ordered by their priority.)
ALPNProtocols
: An array or Buffer
of possible ALPN\nprotocols. (Protocols should be ordered by their priority.) When\nthe server receives both NPN and ALPN extensions from the client,\nALPN takes precedence over NPN and the server does not send an NPN\nextension to the client.
SNICallback(servername, cb)
: A function that will be called if the client\nsupports SNI TLS extension. Two arguments will be passed to it:\nservername
and cb
. SNICallback
should invoke cb(null, ctx)
, where\nctx
is a SecureContext instance. (tls.createSecureContext(...)
can be\nused to get a proper SecureContext.) If SNICallback
wasn't provided the\ndefault callback with high-level API will be used (see below).
sessionTimeout
: An integer specifying the number of seconds after which\nthe TLS session identifiers and TLS session tickets created by the server\nwill time out. See [SSL_CTX_set_timeout] for more details.
ticketKeys
: A 48-byte Buffer
instance consisting of a 16-byte prefix,\na 16-byte HMAC key, and a 16-byte AES key. This can be used to accept TLS\nsession tickets on multiple instances of the TLS server.
NOTE: Automatically shared between cluster
module workers.
sessionIdContext
: A string containing an opaque identifier for session\nresumption. If requestCert
is true
, the default is a 128 bit\ntruncated SHA1 hash value generated from the command-line. Otherwise, a\ndefault is not provided.
secureProtocol
: The SSL method to use, e.g., SSLv3_method
to force\nSSL version 3. The possible values depend on the version of OpenSSL\ninstalled in the environment and are defined in the constant [SSL_METHODS][].
Here is a simple example echo server:\n\n
\nconst tls = require('tls');\nconst fs = require('fs');\n\nconst options = {\n key: fs.readFileSync('server-key.pem'),\n cert: fs.readFileSync('server-cert.pem'),\n\n // This is necessary only if using the client certificate authentication.\n requestCert: true,\n\n // This is necessary only if the client uses the self-signed certificate.\n ca: [ fs.readFileSync('client-cert.pem') ]\n};\n\nvar server = tls.createServer(options, (socket) => {\n console.log('server connected',\n socket.authorized ? 'authorized' : 'unauthorized');\n socket.write('welcome!\\n');\n socket.setEncoding('utf8');\n socket.pipe(socket);\n});\nserver.listen(8000, () => {\n console.log('server bound');\n});
\nOr\n\n
\nconst tls = require('tls');\nconst fs = require('fs');\n\nconst options = {\n pfx: fs.readFileSync('server.pfx'),\n\n // This is necessary only if using the client certificate authentication.\n requestCert: true,\n\n};\n\nvar server = tls.createServer(options, (socket) => {\n console.log('server connected',\n socket.authorized ? 'authorized' : 'unauthorized');\n socket.write('welcome!\\n');\n socket.setEncoding('utf8');\n socket.pipe(socket);\n});\nserver.listen(8000, () => {\n console.log('server bound');\n});
\nYou can test this server by connecting to it with openssl s_client
:\n\n
openssl s_client -connect 127.0.0.1:8000
\n",
"signatures": [
{
"params": [
{
"name": "options"
},
{
"name": "secureConnectionListener",
"optional": true
}
]
}
]
},
{
"textRaw": "tls.getCiphers()",
"type": "method",
"name": "getCiphers",
"desc": "Returns an array with the names of the supported SSL ciphers.\n\n
\nExample:\n\n
\nvar ciphers = tls.getCiphers();\nconsole.log(ciphers); // ['AES128-SHA', 'AES256-SHA', ...]
\n",
"signatures": [
{
"params": []
}
]
}
],
"type": "module",
"displayName": "TLS (SSL)"
},
{
"textRaw": "TTY",
"name": "tty",
"stability": 2,
"stabilityText": "Stable",
"desc": "The tty
module houses the tty.ReadStream
and tty.WriteStream
classes. In\nmost cases, you will not need to use this module directly.\n\n
When Node.js detects that it is being run inside a TTY context, then process.stdin
\nwill be a tty.ReadStream
instance and process.stdout
will be\na tty.WriteStream
instance. The preferred way to check if Node.js is being run\nin a TTY context is to check process.stdout.isTTY
:\n\n
$ node -p -e "Boolean(process.stdout.isTTY)"\ntrue\n$ node -p -e "Boolean(process.stdout.isTTY)" | cat\nfalse
\n",
"classes": [
{
"textRaw": "Class: ReadStream",
"type": "class",
"name": "ReadStream",
"desc": "A net.Socket
subclass that represents the readable portion of a tty. In normal\ncircumstances, process.stdin
will be the only tty.ReadStream
instance in any\nNode.js program (only when isatty(0)
is true).\n\n
A Boolean
that is initialized to false
. It represents the current "raw" state\nof the tty.ReadStream
instance.\n\n
mode
should be true
or false
. This sets the properties of the\ntty.ReadStream
to act either as a raw device or default. isRaw
will be set\nto the resulting mode.\n\n
A net.Socket
subclass that represents the writable portion of a tty. In normal\ncircumstances, process.stdout
will be the only tty.WriteStream
instance\never created (and only when isatty(1)
is true).\n\n
function () {}
\n\n
Emitted by refreshSize()
when either of the columns
or rows
properties\nhas changed.\n\n
process.stdout.on('resize', () => {\n console.log('screen size has changed!');\n console.log(`${process.stdout.columns}x${process.stdout.rows}`);\n});
\n",
"params": []
}
],
"properties": [
{
"textRaw": "ws.columns",
"name": "columns",
"desc": "A Number
that gives the number of columns the TTY currently has. This property\ngets updated on 'resize'
events.\n\n
A Number
that gives the number of rows the TTY currently has. This property\ngets updated on 'resize'
events.\n\n
Returns true
or false
depending on if the fd
is associated with a\nterminal.\n\n
This module has utilities for URL resolution and parsing.\nCall require('url')
to use it.\n\n
Parsed URL objects have some or all of the following fields, depending on\nwhether or not they exist in the URL string. Any parts that are not in the URL\nstring will not be in the parsed object. Examples are shown for the URL\n\n
\n'http://user:pass@host.com:8080/p/a/t/h?query=string#hash'
\n\n
href
: The full URL that was originally parsed. Both the protocol and host are lowercased.
Example: 'http://user:pass@host.com:8080/p/a/t/h?query=string#hash'
protocol
: The request protocol, lowercased.
Example: 'http:'
slashes
: The protocol requires slashes after the colon.
Example: true or false
\nhost
: The full lowercased host portion of the URL, including port\ninformation.
Example: 'host.com:8080'
auth
: The authentication information portion of a URL.
Example: 'user:pass'
hostname
: Just the lowercased hostname portion of the host.
Example: 'host.com'
port
: The port number portion of the host.
Example: '8080'
pathname
: The path section of the URL, that comes after the host and\nbefore the query, including the initial slash if present. No decoding is\nperformed.
Example: '/p/a/t/h'
search
: The 'query string' portion of the URL, including the leading\nquestion mark.
Example: '?query=string'
path
: Concatenation of pathname
and search
. No decoding is performed.
Example: '/p/a/t/h?query=string'
query
: Either the 'params' portion of the query string, or a\nquerystring-parsed object.
Example: 'query=string'
or {'query':'string'}
hash
: The 'fragment' portion of the URL including the pound-sign.
Example: '#hash'
Spaces (' '
) and the following characters will be automatically escaped in the\nproperties of URL objects:\n\n
< > " ` \\r \\n \\t { } | \\ ^ '
\nThe following methods are provided by the URL module:\n\n
\n", "type": "module", "displayName": "Escaped Characters" } ], "type": "module", "displayName": "URL Parsing" } ], "methods": [ { "textRaw": "url.format(urlObj)", "type": "method", "name": "format", "desc": "Take a parsed URL object, and return a formatted URL string.\n\n
\nHere's how the formatting process works:\n\n
\nhref
will be ignored.path
will be ignored.protocol
is treated the same with or without the trailing :
(colon).http
, https
, ftp
, gopher
, file
will be\npostfixed with ://
(colon-slash-slash) as long as host
/hostname
are present.mailto
, xmpp
, aim
, sftp
, foo
, etc will\nbe postfixed with :
(colon).slashes
set to true
if the protocol requires ://
(colon-slash-slash)mongodb://localhost:8000/
, or if host
/hostname
are absent.auth
will be used if present.hostname
will only be used if host
is absent.port
will only be used if host
is absent.host
will be used in place of hostname
and port
.pathname
is treated the same with or without the leading /
(slash).query
(object; see querystring
) will only be used if search
is absent.search
will be used in place of query
.?
(question mark).hash
is treated the same with or without the leading #
(pound sign, anchor).Take a URL string, and return an object.\n\n
\nPass true
as the second argument to also parse the query string using the\nquerystring
module. If true
then the query
property will always be\nassigned an object, and the search
property will always be a (possibly\nempty) string. If false
then the query
property will not be parsed or\ndecoded. Defaults to false
.\n\n
Pass true
as the third argument to treat //foo/bar
as\n{ host: 'foo', pathname: '/bar' }
rather than\n{ pathname: '//foo/bar' }
. Defaults to false
.\n\n
Take a base URL, and a href URL, and resolve them as a browser would for\nan anchor tag. Examples:\n\n
\nurl.resolve('/one/two/three', 'four') // '/one/two/four'\nurl.resolve('http://example.com/', '/one') // 'http://example.com/one'\nurl.resolve('http://example.com/one', '/two') // 'http://example.com/two'
\n",
"signatures": [
{
"params": [
{
"name": "from"
},
{
"name": "to"
}
]
}
]
}
],
"type": "module",
"displayName": "URL"
},
{
"textRaw": "util",
"name": "util",
"stability": 2,
"stabilityText": "Stable",
"desc": "These functions are in the module 'util'
. Use require('util')
to\naccess them.\n\n
The util
module is primarily designed to support the needs of Node.js's\ninternal APIs. Many of these utilities are useful for your own\nprograms. If you find that these functions are lacking for your\npurposes, however, you are encouraged to write your own utilities. We\nare not interested in any future additions to the util
module that\nare unnecessary for Node.js's internal functionality.\n\n
Deprecated predecessor of console.error
.\n\n
This is used to create a function which conditionally writes to stderr\nbased on the existence of a NODE_DEBUG
environment variable. If the\nsection
name appears in that environment variable, then the returned\nfunction will be similar to console.error()
. If not, then the\nreturned function is a no-op.\n\n
For example:\n\n
\nvar debuglog = util.debuglog('foo');\n\nvar bar = 123;\ndebuglog('hello from foo [%d]', bar);
\nIf this program is run with NODE_DEBUG=foo
in the environment, then\nit will output something like:\n\n
FOO 3245: hello from foo [123]
\nwhere 3245
is the process id. If it is not run with that\nenvironment variable set, then it will not print anything.\n\n
You may separate multiple NODE_DEBUG
environment variables with a\ncomma. For example, NODE_DEBUG=fs,net,tls
.\n\n
Marks that a method should not be used any more.\n\n
\nconst util = require('util');\n\nexports.puts = util.deprecate(() => {\n for (var i = 0, len = arguments.length; i < len; ++i) {\n process.stdout.write(arguments[i] + '\\n');\n }\n}, 'util.puts: Use console.log instead');
\nIt returns a modified function which warns once by default.\n\n
\nIf --no-deprecation
is set then this function is a NO-OP. Configurable\nat run-time through the process.noDeprecation
boolean (only effective\nwhen set before a module is loaded.)\n\n
If --trace-deprecation
is set, a warning and a stack trace are logged\nto the console the first time the deprecated API is used. Configurable\nat run-time through the process.traceDeprecation
boolean.\n\n
If --throw-deprecation
is set then the application throws an exception\nwhen the deprecated API is used. Configurable at run-time through the\nprocess.throwDeprecation
boolean.\n\n
process.throwDeprecation
takes precedence over process.traceDeprecation
.\n\n
Deprecated predecessor of console.error
.\n\n
Returns a formatted string using the first argument as a printf
-like format.\n\n
The first argument is a string that contains zero or more placeholders.\nEach placeholder is replaced with the converted value from its corresponding\nargument. Supported placeholders are:\n\n
\n%s
- String.%d
- Number (both integer and float).%j
- JSON. Replaced with the string '[Circular]'
if the argument\ncontains circular references.%%
- single percent sign ('%'
). This does not consume an argument.If the placeholder does not have a corresponding argument, the placeholder is\nnot replaced.\n\n
\nutil.format('%s:%s', 'foo'); // 'foo:%s'
\nIf there are more arguments than placeholders, the extra arguments are\ncoerced to strings (for objects and symbols, util.inspect()
is used)\nand then concatenated, delimited by a space.\n\n
util.format('%s:%s', 'foo', 'bar', 'baz'); // 'foo:bar baz'
\nIf the first argument is not a format string then util.format()
returns\na string that is the concatenation of all its arguments separated by spaces.\nEach argument is converted to a string with util.inspect()
.\n\n
util.format(1, 2, 3); // '1 2 3'
\n",
"signatures": [
{
"params": [
{
"name": "format"
},
{
"name": "...",
"optional": true
}
]
}
]
},
{
"textRaw": "util.inherits(constructor, superConstructor)",
"type": "method",
"name": "inherits",
"desc": "Inherit the prototype methods from one [constructor][] into another. The\nprototype of constructor
will be set to a new object created from\nsuperConstructor
.\n\n
As an additional convenience, superConstructor
will be accessible\nthrough the constructor.super_
property.\n\n
const util = require('util');\nconst EventEmitter = require('events');\n\nfunction MyStream() {\n EventEmitter.call(this);\n}\n\nutil.inherits(MyStream, EventEmitter);\n\nMyStream.prototype.write = function(data) {\n this.emit('data', data);\n}\n\nvar stream = new MyStream();\n\nconsole.log(stream instanceof EventEmitter); // true\nconsole.log(MyStream.super_ === EventEmitter); // true\n\nstream.on('data', (data) => {\n console.log(`Received data: "${data}"`);\n})\nstream.write('It works!'); // Received data: "It works!"
\n",
"signatures": [
{
"params": [
{
"name": "constructor"
},
{
"name": "superConstructor"
}
]
}
]
},
{
"textRaw": "util.inspect(object[, options])",
"type": "method",
"name": "inspect",
"desc": "Return a string representation of object
, which is useful for debugging.\n\n
An optional options object may be passed that alters certain aspects of the\nformatted string:\n\n
\nshowHidden
- if true
then the object's non-enumerable and symbol\nproperties will be shown too. Defaults to false
.
depth
- tells inspect
how many times to recurse while formatting the\nobject. This is useful for inspecting large complicated objects. Defaults to\n2
. To make it recurse indefinitely pass null
.
colors
- if true
, then the output will be styled with ANSI color codes.\nDefaults to false
. Colors are customizable, see [Customizing\nutil.inspect
colors][].
customInspect
- if false
, then custom inspect(depth, opts)
functions\ndefined on the objects being inspected won't be called. Defaults to true
.
showProxy
- if true
, then objects and functions that are Proxy objects\nwill be introspected to show their target
and hander
objects. Defaults to\nfalse
.
maxArrayLength
- specifies the maximum number of Array and TypedArray\nelements to include when formatting. Defaults to 100
. Set to null
to\nshow all array elements. Set to 0
or negative to show no array elements.
Example of inspecting all properties of the util
object:\n\n
const util = require('util');\n\nconsole.log(util.inspect(util, { showHidden: true, depth: null }));
\nValues may supply their own custom inspect(depth, opts)
functions, when\ncalled they receive the current depth in the recursive inspection, as well as\nthe options object passed to util.inspect()
.\n\n
Color output (if enabled) of util.inspect
is customizable globally\nvia util.inspect.styles
and util.inspect.colors
objects.\n\n
util.inspect.styles
is a map assigning each style a color\nfrom util.inspect.colors
.\nHighlighted styles and their default values are:\n number
(yellow)\n boolean
(yellow)\n string
(green)\n date
(magenta)\n regexp
(red)\n null
(bold)\n undefined
(grey)\n special
- only function at this time (cyan)\n * name
(intentionally no styling)\n\n
Predefined color codes are: white
, grey
, black
, blue
, cyan
,\ngreen
, magenta
, red
and yellow
.\nThere are also bold
, italic
, underline
and inverse
codes.\n\n
Objects also may define their own inspect(depth)
function which util.inspect()
\nwill invoke and use the result of when inspecting the object:\n\n
const util = require('util');\n\nvar obj = { name: 'nate' };\nobj.inspect = function(depth) {\n return `{${this.name}}`;\n};\n\nutil.inspect(obj);\n // "{nate}"
\nYou may also return another Object entirely, and the returned String will be\nformatted according to the returned Object. This is similar to how\nJSON.stringify()
works:\n\n
var obj = { foo: 'this will not show up in the inspect() output' };\nobj.inspect = function(depth) {\n return { bar: 'baz' };\n};\n\nutil.inspect(obj);\n // "{ bar: 'baz' }"
\n"
}
],
"signatures": [
{
"params": [
{
"name": "object"
},
{
"name": "options",
"optional": true
}
]
}
]
},
{
"textRaw": "util.isArray(object)",
"type": "method",
"name": "isArray",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Internal alias for [Array.isArray
][].\n\n
Returns true
if the given "object" is an Array
. Otherwise, returns false
.\n\n
const util = require('util');\n\nutil.isArray([])\n // true\nutil.isArray(new Array)\n // true\nutil.isArray({})\n // false
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isBoolean(object)",
"type": "method",
"name": "isBoolean",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is a Boolean
. Otherwise, returns false
.\n\n
const util = require('util');\n\nutil.isBoolean(1)\n // false\nutil.isBoolean(0)\n // false\nutil.isBoolean(false)\n // true
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isBuffer(object)",
"type": "method",
"name": "isBuffer",
"stability": 0,
"stabilityText": "Deprecated: Use [`Buffer.isBuffer()`][] instead.",
"desc": "Returns true
if the given "object" is a Buffer
. Otherwise, returns false
.\n\n
const util = require('util');\n\nutil.isBuffer({ length: 0 })\n // false\nutil.isBuffer([])\n // false\nutil.isBuffer(Buffer.from('hello world'))\n // true
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isDate(object)",
"type": "method",
"name": "isDate",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is a Date
. Otherwise, returns false
.\n\n
const util = require('util');\n\nutil.isDate(new Date())\n // true\nutil.isDate(Date())\n // false (without 'new' returns a String)\nutil.isDate({})\n // false
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isError(object)",
"type": "method",
"name": "isError",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is an [Error
][]. Otherwise, returns\nfalse
.\n\n
const util = require('util');\n\nutil.isError(new Error())\n // true\nutil.isError(new TypeError())\n // true\nutil.isError({ name: 'Error', message: 'an error occurred' })\n // false
\nNote that this method relies on Object.prototype.toString()
behavior. It is\npossible to obtain an incorrect result when the object
argument manipulates\n@@toStringTag
.\n\n
const util = require('util');\nconst obj = { name: 'Error', message: 'an error occurred' };\n\nutil.isError(obj);\n // false\nobj[Symbol.toStringTag] = 'Error';\nutil.isError(obj);\n // true
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isFunction(object)",
"type": "method",
"name": "isFunction",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is a Function
. Otherwise, returns\nfalse
.\n\n
const util = require('util');\n\nfunction Foo() {}\nvar Bar = function() {};\n\nutil.isFunction({})\n // false\nutil.isFunction(Foo)\n // true\nutil.isFunction(Bar)\n // true
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isNull(object)",
"type": "method",
"name": "isNull",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is strictly null
. Otherwise, returns\nfalse
.\n\n
const util = require('util');\n\nutil.isNull(0)\n // false\nutil.isNull(undefined)\n // false\nutil.isNull(null)\n // true
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isNullOrUndefined(object)",
"type": "method",
"name": "isNullOrUndefined",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is null
or undefined
. Otherwise,\nreturns false
.\n\n
const util = require('util');\n\nutil.isNullOrUndefined(0)\n // false\nutil.isNullOrUndefined(undefined)\n // true\nutil.isNullOrUndefined(null)\n // true
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isNumber(object)",
"type": "method",
"name": "isNumber",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is a Number
. Otherwise, returns false
.\n\n
const util = require('util');\n\nutil.isNumber(false)\n // false\nutil.isNumber(Infinity)\n // true\nutil.isNumber(0)\n // true\nutil.isNumber(NaN)\n // true
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isObject(object)",
"type": "method",
"name": "isObject",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is strictly an Object
and not a\nFunction
. Otherwise, returns false
.\n\n
const util = require('util');\n\nutil.isObject(5)\n // false\nutil.isObject(null)\n // false\nutil.isObject({})\n // true\nutil.isObject(function(){})\n // false
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isPrimitive(object)",
"type": "method",
"name": "isPrimitive",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is a primitive type. Otherwise, returns\nfalse
.\n\n
const util = require('util');\n\nutil.isPrimitive(5)\n // true\nutil.isPrimitive('foo')\n // true\nutil.isPrimitive(false)\n // true\nutil.isPrimitive(null)\n // true\nutil.isPrimitive(undefined)\n // true\nutil.isPrimitive({})\n // false\nutil.isPrimitive(function() {})\n // false\nutil.isPrimitive(/^$/)\n // false\nutil.isPrimitive(new Date())\n // false
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isRegExp(object)",
"type": "method",
"name": "isRegExp",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is a RegExp
. Otherwise, returns false
.\n\n
const util = require('util');\n\nutil.isRegExp(/some regexp/)\n // true\nutil.isRegExp(new RegExp('another regexp'))\n // true\nutil.isRegExp({})\n // false
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isString(object)",
"type": "method",
"name": "isString",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is a String
. Otherwise, returns false
.\n\n
const util = require('util');\n\nutil.isString('')\n // true\nutil.isString('foo')\n // true\nutil.isString(String('foo'))\n // true\nutil.isString(5)\n // false
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isSymbol(object)",
"type": "method",
"name": "isSymbol",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is a Symbol
. Otherwise, returns false
.\n\n
const util = require('util');\n\nutil.isSymbol(5)\n // false\nutil.isSymbol('foo')\n // false\nutil.isSymbol(Symbol('foo'))\n // true
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.isUndefined(object)",
"type": "method",
"name": "isUndefined",
"stability": 0,
"stabilityText": "Deprecated",
"desc": "Returns true
if the given "object" is undefined
. Otherwise, returns false
.\n\n
const util = require('util');\n\nvar foo;\nutil.isUndefined(5)\n // false\nutil.isUndefined(foo)\n // true\nutil.isUndefined(null)\n // false
\n",
"signatures": [
{
"params": [
{
"name": "object"
}
]
}
]
},
{
"textRaw": "util.log(string)",
"type": "method",
"name": "log",
"stability": 0,
"stabilityText": "Deprecated: Use a third party module instead.",
"desc": "Output with timestamp on stdout
.\n\n
require('util').log('Timestamped message.');
\n",
"signatures": [
{
"params": [
{
"name": "string"
}
]
}
]
},
{
"textRaw": "util.print([...])",
"type": "method",
"name": "print",
"stability": 0,
"stabilityText": "Deprecated: Use [`console.log()`][] instead.",
"desc": "Deprecated predecessor of console.log
.\n\n
Deprecated predecessor of console.log
.\n\n
_extend
was never intended to be used outside of internal NodeJS modules. The\ncommunity found and used it anyway.\n\n
It is deprecated and should not be used in new code. JavaScript comes with very\nsimilar built-in functionality through Object.assign
.\n\n
This module exposes events and interfaces specific to the version of [V8][]\nbuilt with Node.js. These interfaces are subject to change by upstream and are\ntherefore not covered under the stability index.\n\n
\n", "methods": [ { "textRaw": "getHeapStatistics()", "type": "method", "name": "getHeapStatistics", "desc": "Returns an object with the following properties\n\n
\n{\n total_heap_size: 7326976,\n total_heap_size_executable: 4194304,\n total_physical_size: 7326976,\n total_available_size: 1152656,\n used_heap_size: 3476208,\n heap_size_limit: 1535115264\n}
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "getHeapSpaceStatistics()",
"type": "method",
"name": "getHeapSpaceStatistics",
"desc": "Returns statistics about the V8 heap spaces, i.e. the segments which make up\nthe V8 heap. Order of heap spaces nor availability of a heap space can be\nguaranteed as the statistics are provided via the V8 GetHeapSpaceStatistics
\nfunction.\n\n
Example result:\n\n
\n[\n {\n "space_name": "new_space",\n "space_size": 2063872,\n "space_used_size": 951112,\n "space_available_size": 80824,\n "physical_space_size": 2063872\n },\n {\n "space_name": "old_space",\n "space_size": 3090560,\n "space_used_size": 2493792,\n "space_available_size": 0,\n "physical_space_size": 3090560\n },\n {\n "space_name": "code_space",\n "space_size": 1260160,\n "space_used_size": 644256,\n "space_available_size": 960,\n "physical_space_size": 1260160\n },\n {\n "space_name": "map_space",\n "space_size": 1094160,\n "space_used_size": 201608,\n "space_available_size": 0,\n "physical_space_size": 1094160\n },\n {\n "space_name": "large_object_space",\n "space_size": 0,\n "space_used_size": 0,\n "space_available_size": 1490980608,\n "physical_space_size": 0\n }\n]
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "setFlagsFromString(string)",
"type": "method",
"name": "setFlagsFromString",
"desc": "Set additional V8 command line flags. Use with care; changing settings\nafter the VM has started may result in unpredictable behavior, including\ncrashes and data loss. Or it may simply do nothing.\n\n
\nThe V8 options available for a version of Node.js may be determined by running\nnode --v8-options
. An unofficial, community-maintained list of options\nand their effects is available [here][].\n\n
Usage:\n\n
\n// Print GC events to stdout for one minute.\nconst v8 = require('v8');\nv8.setFlagsFromString('--trace_gc');\nsetTimeout(function() { v8.setFlagsFromString('--notrace_gc'); }, 60e3);
\n",
"signatures": [
{
"params": [
{
"name": "string"
}
]
}
]
}
],
"type": "module",
"displayName": "V8"
},
{
"textRaw": "Executing JavaScript",
"name": "vm",
"stability": 2,
"stabilityText": "Stable",
"desc": "You can access this module with:\n\n
\nconst vm = require('vm');
\nJavaScript code can be compiled and run immediately or compiled, saved, and run\nlater.\n\n
\n", "classes": [ { "textRaw": "Class: Script", "type": "class", "name": "Script", "desc": "A class for holding precompiled scripts, and running them in specific sandboxes.\n\n
\n", "methods": [ { "textRaw": "new vm.Script(code, options)", "type": "method", "name": "Script", "desc": "Creating a new Script
compiles code
but does not run it. Instead, the\ncreated vm.Script
object represents this compiled code. This script can be run\nlater many times using methods below. The returned script is not bound to any\nglobal object. It is bound before each run, just for that run.\n\n
The options when creating a script are:\n\n
\nfilename
: allows you to control the filename that shows up in any stack\ntraces produced from this script.lineOffset
: allows you to add an offset to the line number that is\ndisplayed in stack tracescolumnOffset
: allows you to add an offset to the column number that is\ndisplayed in stack tracesdisplayErrors
: if true
, on error, attach the line of code that caused\nthe error to the stack trace. Applies only to syntax errors compiling the\ncode; errors while running the code are controlled by the options to the\nscript's methods.timeout
: a number of milliseconds to execute code
before terminating\nexecution. If execution is terminated, an [Error
][] will be thrown.cachedData
: an optional Buffer
with V8's code cache data for the supplied\nsource. When supplied cachedDataRejected
value will be set to either\ntrue
or false
depending on acceptance of the data by V8.produceCachedData
: if true
and no cachedData
is present - V8 tries to\nproduce code cache data for code
. Upon success, a Buffer
with V8's code\ncache data will be produced and stored in cachedData
property of the\nreturned vm.Script
instance. cachedDataProduced
value will be set to\neither true
or false
depending on whether code cache data is produced\nsuccessfully.Similar to [vm.runInContext()
][] but a method of a precompiled Script
\nobject. script.runInContext()
runs script
's compiled code in\ncontextifiedSandbox
and returns the result. Running code does not have access\nto local scope.\n\n
script.runInContext()
takes the same options as\n[script.runInThisContext()
][].\n\n
Example: compile code that increments a global variable and sets one, then\nexecute the code multiple times. These globals are contained in the sandbox.\n\n
\nconst util = require('util');\nconst vm = require('vm');\n\nvar sandbox = {\n animal: 'cat',\n count: 2\n};\n\nvar context = new vm.createContext(sandbox);\nvar script = new vm.Script('count += 1; name = "kitty"');\n\nfor (var i = 0; i < 10; ++i) {\n script.runInContext(context);\n}\n\nconsole.log(util.inspect(sandbox));\n\n// { animal: 'cat', count: 12, name: 'kitty' }
\nNote that running untrusted code is a tricky business requiring great care.\nscript.runInContext()
is quite useful, but safely running untrusted code\nrequires a separate process.\n\n
Similar to [vm.runInNewContext()
][] but a method of a precompiled Script
\nobject. script.runInNewContext()
contextifies sandbox
if passed or creates a\nnew contextified sandbox if it's omitted, and then runs script
's compiled code\nwith the sandbox as the global object and returns the result. Running code does\nnot have access to local scope.\n\n
script.runInNewContext()
takes the same options as\n[script.runInThisContext()
][].\n\n
Example: compile code that sets a global variable, then execute the code\nmultiple times in different contexts. These globals are set on and contained in\nthe sandboxes.\n\n
\nconst util = require('util');\nconst vm = require('vm');\n\nconst sandboxes = [{}, {}, {}];\n\nconst script = new vm.Script('globalVar = "set"');\n\nsandboxes.forEach((sandbox) => {\n script.runInNewContext(sandbox);\n});\n\nconsole.log(util.inspect(sandboxes));\n\n// [{ globalVar: 'set' }, { globalVar: 'set' }, { globalVar: 'set' }]
\nNote that running untrusted code is a tricky business requiring great care.\nscript.runInNewContext()
is quite useful, but safely running untrusted code\nrequires a separate process.\n\n
Similar to [vm.runInThisContext()
][] but a method of a precompiled Script
\nobject. script.runInThisContext()
runs script
's compiled code and returns\nthe result. Running code does not have access to local scope, but does have\naccess to the current global
object.\n\n
Example of using script.runInThisContext()
to compile code once and run it\nmultiple times:\n\n
const vm = require('vm');\n\nglobal.globalVar = 0;\n\nconst script = new vm.Script('globalVar += 1', { filename: 'myfile.vm' });\n\nfor (var i = 0; i < 1000; ++i) {\n script.runInThisContext();\n}\n\nconsole.log(globalVar);\n\n// 1000
\nThe options for running a script are:\n\n
\nfilename
: allows you to control the filename that shows up in any stack\ntraces produced.lineOffset
: allows you to add an offset to the line number that is\ndisplayed in stack tracescolumnOffset
: allows you to add an offset to the column number that is\ndisplayed in stack tracesdisplayErrors
: if true
, on error, attach the line of code that caused\nthe error to the stack trace. Applies only to runtime errors executing the\ncode; it is impossible to create a Script
instance with syntax errors, as\nthe constructor will throw.timeout
: a number of milliseconds to execute the script before terminating\nexecution. If execution is terminated, an [Error
][] will be thrown.If given a sandbox
object, will "contextify" that sandbox so that it can be\nused in calls to [vm.runInContext()
][] or [script.runInContext()
][]. Inside\nscripts run as such, sandbox
will be the global object, retaining all its\nexisting properties but also having the built-in objects and functions any\nstandard [global object][] has. Outside of scripts run by the vm module,\nsandbox
will be unchanged.\n\n
If not given a sandbox object, returns a new, empty contextified sandbox object\nyou can use.\n\n
\nThis function is useful for creating a sandbox that can be used to run multiple\nscripts, e.g. if you were emulating a web browser it could be used to create a\nsingle sandbox representing a window's global object, then run all <script>
\ntags together inside that sandbox.\n\n
Returns whether or not a sandbox object has been contextified by calling\n[vm.createContext()
][] on it.\n\n
vm.runInContext()
compiles code
, then runs it in contextifiedSandbox
and\nreturns the result. Running code does not have access to local scope. The\ncontextifiedSandbox
object must have been previously contextified via\n[vm.createContext()
][]; it will be used as the global object for code
.\n\n
vm.runInContext()
takes the same options as [vm.runInThisContext()
][].\n\n
Example: compile and execute different scripts in a single existing context.\n\n
\nconst util = require('util');\nconst vm = require('vm');\n\nconst sandbox = { globalVar: 1 };\nvm.createContext(sandbox);\n\nfor (var i = 0; i < 10; ++i) {\n vm.runInContext('globalVar *= 2;', sandbox);\n}\nconsole.log(util.inspect(sandbox));\n\n// { globalVar: 1024 }
\nNote that running untrusted code is a tricky business requiring great care.\nvm.runInContext()
is quite useful, but safely running untrusted code requires\na separate process.\n\n
vm.runInDebugContext()
compiles and executes code
inside the V8 debug\ncontext. The primary use case is to get access to the V8 debug object:\n\n
const Debug = vm.runInDebugContext('Debug');\nDebug.scripts().forEach((script) => { console.log(script.name); });
\nNote that the debug context and object are intrinsically tied to V8's debugger\nimplementation and may change (or even get removed) without prior warning.\n\n
\nThe debug object can also be exposed with the --expose_debug_as=
switch.\n\n
vm.runInNewContext()
compiles code
, contextifies sandbox
if passed or\ncreates a new contextified sandbox if it's omitted, and then runs the code with\nthe sandbox as the global object and returns the result.\n\n
vm.runInNewContext()
takes the same options as [vm.runInThisContext()
][].\n\n
Example: compile and execute code that increments a global variable and sets a\nnew one. These globals are contained in the sandbox.\n\n
\nconst util = require('util');\nconst vm = require('vm');\n\nconst sandbox = {\n animal: 'cat',\n count: 2\n};\n\nvm.runInNewContext('count += 1; name = "kitty"', sandbox);\nconsole.log(util.inspect(sandbox));\n\n// { animal: 'cat', count: 3, name: 'kitty' }
\nNote that running untrusted code is a tricky business requiring great care.\nvm.runInNewContext()
is quite useful, but safely running untrusted code requires\na separate process.\n\n
vm.runInThisContext()
compiles code
, runs it and returns the result. Running\ncode does not have access to local scope, but does have access to the current\nglobal
object.\n\n
Example of using vm.runInThisContext()
and [eval()
][] to run the same code:\n\n
const vm = require('vm');\nvar localVar = 'initial value';\n\nconst vmResult = vm.runInThisContext('localVar = "vm";');\nconsole.log('vmResult: ', vmResult);\nconsole.log('localVar: ', localVar);\n\nconst evalResult = eval('localVar = "eval";');\nconsole.log('evalResult: ', evalResult);\nconsole.log('localVar: ', localVar);\n\n// vmResult: 'vm', localVar: 'initial value'\n// evalResult: 'eval', localVar: 'eval'
\nvm.runInThisContext()
does not have access to the local scope, so localVar
\nis unchanged. [eval()
][] does have access to the local scope, so localVar
is\nchanged.\n\n
In this way vm.runInThisContext()
is much like an [indirect eval()
call][],\ne.g. (0,eval)('code')
. However, it also has the following additional options:\n\n
filename
: allows you to control the filename that shows up in any stack\ntraces produced.lineOffset
: allows you to add an offset to the line number that is\ndisplayed in stack tracescolumnOffset
: allows you to add an offset to the column number that is\ndisplayed in stack tracesdisplayErrors
: if true
, on error, attach the line of code that caused\nthe error to the stack trace. Will capture both syntax errors from compiling\ncode
and runtime errors thrown by executing the compiled code. Defaults to\ntrue
.timeout
: a number of milliseconds to execute code
before terminating\nexecution. If execution is terminated, an [Error
][] will be thrown.The context of .runInThisContext()
refers to the V8 context. The code passed\nto this VM context will have it's own isolated scope. To run a simple web server\nusing the http
module, for instance, the code passed to the context must either\ncall require('http')
on its own, or have a reference to the http
module passed\nto it. For instance:\n\n
'use strict';\nconst vm = require('vm');\n\nlet code =\n`(function(require) {\n\n const http = require('http');\n\n http.createServer( (request, response) => {\n response.writeHead(200, {'Content-Type': 'text/plain'});\n response.end('Hello World\\\\n');\n }).listen(8124);\n\n console.log('Server running at http://127.0.0.1:8124/');\n })`;\n\n vm.runInThisContext(code)(require);
\nNote: require()
in the above case shares the state with context it is passed\nfrom. This might introduce risks when unknown code is executed, e.g. altering\nobjects from the calling thread's context in unwanted ways. It is advisable to\nrun vm
code in a separate process.\n\n
You can access this module with:\n\n
\nconst zlib = require('zlib');
\nThis provides bindings to Gzip/Gunzip, Deflate/Inflate, and\nDeflateRaw/InflateRaw classes. Each class takes the same options, and\nis a readable/writable Stream.\n\n
\nCompressing or decompressing a file can be done by piping an\nfs.ReadStream into a zlib stream, then into an fs.WriteStream.\n\n
\nconst gzip = zlib.createGzip();\nconst fs = require('fs');\nconst inp = fs.createReadStream('input.txt');\nconst out = fs.createWriteStream('input.txt.gz');\n\ninp.pipe(gzip).pipe(out);
\nCompressing or decompressing data in one step can be done by using\nthe convenience methods.\n\n
\nconst input = '.................................';\nzlib.deflate(input, (err, buffer) => {\n if (!err) {\n console.log(buffer.toString('base64'));\n } else {\n // handle error\n }\n});\n\nconst buffer = Buffer.from('eJzT0yMAAGTvBe8=', 'base64');\nzlib.unzip(buffer, (err, buffer) => {\n if (!err) {\n console.log(buffer.toString());\n } else {\n // handle error\n }\n});
\nTo use this module in an HTTP client or server, use the [accept-encoding][]\non requests, and the [content-encoding][] header on responses.\n\n
\nNote: these examples are drastically simplified to show\nthe basic concept. Zlib encoding can be expensive, and the results\nought to be cached. See [Memory Usage Tuning][] for more information\non the speed/memory/compression tradeoffs involved in zlib usage.\n\n
\n// client request example\nconst zlib = require('zlib');\nconst http = require('http');\nconst fs = require('fs');\nconst request = http.get({ host: 'izs.me',\n path: '/',\n port: 80,\n headers: { 'accept-encoding': 'gzip,deflate' } });\nrequest.on('response', (response) => {\n var output = fs.createWriteStream('izs.me_index.html');\n\n switch (response.headers['content-encoding']) {\n // or, just use zlib.createUnzip() to handle both cases\n case 'gzip':\n response.pipe(zlib.createGunzip()).pipe(output);\n break;\n case 'deflate':\n response.pipe(zlib.createInflate()).pipe(output);\n break;\n default:\n response.pipe(output);\n break;\n }\n});\n\n// server example\n// Running a gzip operation on every request is quite expensive.\n// It would be much more efficient to cache the compressed buffer.\nconst zlib = require('zlib');\nconst http = require('http');\nconst fs = require('fs');\nhttp.createServer((request, response) => {\n var raw = fs.createReadStream('index.html');\n var acceptEncoding = request.headers['accept-encoding'];\n if (!acceptEncoding) {\n acceptEncoding = '';\n }\n\n // Note: this is not a conformant accept-encoding parser.\n // See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.3\n if (acceptEncoding.match(/\\bdeflate\\b/)) {\n response.writeHead(200, { 'content-encoding': 'deflate' });\n raw.pipe(zlib.createDeflate()).pipe(response);\n } else if (acceptEncoding.match(/\\bgzip\\b/)) {\n response.writeHead(200, { 'content-encoding': 'gzip' });\n raw.pipe(zlib.createGzip()).pipe(response);\n } else {\n response.writeHead(200, {});\n raw.pipe(response);\n }\n}).listen(1337);
\nBy default, the zlib methods with throw an error when decompressing\ntruncated data. However, if it is known that the data is incomplete, or\nthe desire is to inspect only the beginning of a compressed file, it is\npossible to suppress the default error handling by changing the flushing\nmethod that is used to compressed the last chunk of input data:\n\n
\n// This is a truncated version of the buffer from the above examples\nconst buffer = Buffer.from('eJzT0yMA', 'base64');\n\nzlib.unzip(buffer, { finishFlush: zlib.Z_SYNC_FLUSH }, (err, buffer) => {\n if (!err) {\n console.log(buffer.toString());\n } else {\n // handle error\n }\n});
\nThis will not change the behavior in other error-throwing situations, e.g.\nwhen the input data has an invalid format. Using this method, it will not be\npossible to determine whether the input ended prematurely or lacks the\nintegrity checks, making it necessary to manually check that the\ndecompressed result is valid.\n\n
\n", "miscs": [ { "textRaw": "Memory Usage Tuning", "name": "Memory Usage Tuning", "type": "misc", "desc": "From zlib/zconf.h
, modified to node.js's usage:\n\n
The memory requirements for deflate are (in bytes):\n\n
\n(1 << (windowBits+2)) + (1 << (memLevel+9))
\nthat is: 128K for windowBits=15 + 128K for memLevel = 8\n(default values) plus a few kilobytes for small objects.\n\n
\nFor example, if you want to reduce\nthe default memory requirements from 256K to 128K, set the options to:\n\n
\n{ windowBits: 14, memLevel: 7 }
\nOf course this will generally degrade compression (there's no free lunch).\n\n
\nThe memory requirements for inflate are (in bytes)\n\n
\n1 << windowBits
\nthat is, 32K for windowBits=15 (default value) plus a few kilobytes\nfor small objects.\n\n
\nThis is in addition to a single internal output slab buffer of size\nchunkSize
, which defaults to 16K.\n\n
The speed of zlib compression is affected most dramatically by the\nlevel
setting. A higher level will result in better compression, but\nwill take longer to complete. A lower level will result in less\ncompression, but will be much faster.\n\n
In general, greater memory usage options will mean that node.js has to make\nfewer calls to zlib, since it'll be able to process more data in a\nsingle write
operation. So, this is another factor that affects the\nspeed, at the cost of memory usage.\n\n
All of the constants defined in zlib.h are also defined on\nrequire('zlib')
.\nIn the normal course of operations, you will not need to ever set any of\nthese. They are documented here so that their presence is not\nsurprising. This section is taken almost directly from the\n[zlib documentation][]. See http://zlib.net/manual.html#Constants for more\ndetails.\n\n
Allowed flush values.\n\n
\nzlib.Z_NO_FLUSH
zlib.Z_PARTIAL_FLUSH
zlib.Z_SYNC_FLUSH
zlib.Z_FULL_FLUSH
zlib.Z_FINISH
zlib.Z_BLOCK
zlib.Z_TREES
Return codes for the compression/decompression functions. Negative\nvalues are errors, positive values are used for special but normal\nevents.\n\n
\nzlib.Z_OK
zlib.Z_STREAM_END
zlib.Z_NEED_DICT
zlib.Z_ERRNO
zlib.Z_STREAM_ERROR
zlib.Z_DATA_ERROR
zlib.Z_MEM_ERROR
zlib.Z_BUF_ERROR
zlib.Z_VERSION_ERROR
Compression levels.\n\n
\nzlib.Z_NO_COMPRESSION
zlib.Z_BEST_SPEED
zlib.Z_BEST_COMPRESSION
zlib.Z_DEFAULT_COMPRESSION
Compression strategy.\n\n
\nzlib.Z_FILTERED
zlib.Z_HUFFMAN_ONLY
zlib.Z_RLE
zlib.Z_FIXED
zlib.Z_DEFAULT_STRATEGY
Possible values of the data_type field.\n\n
\nzlib.Z_BINARY
zlib.Z_TEXT
zlib.Z_ASCII
zlib.Z_UNKNOWN
The deflate compression method (the only one supported in this version).\n\n
\nzlib.Z_DEFLATED
For initializing zalloc, zfree, opaque.\n\n
\nzlib.Z_NULL
Each class takes an options object. All options are optional.\n\n
\nNote that some options are only relevant when compressing, and are\nignored by the decompression classes.\n\n
\nzlib.Z_NO_FLUSH
)zlib.Z_FINISH
)See the description of deflateInit2
and inflateInit2
at\n
http://zlib.net/manual.html#Advanced for more information on these.\n\n
\n" }, { "textRaw": "Convenience Methods", "name": "Convenience Methods", "type": "misc", "desc": "All of these take a [Buffer][] or string as the first argument, an optional second\nargument to supply options to the zlib classes and will call the supplied\ncallback with callback(error, result)
.\n\n
Every method has a *Sync
counterpart, which accept the same arguments, but\nwithout a callback.\n\n
Compress a Buffer or string with Deflate.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] }, { "params": [ { "name": "buf" }, { "name": "options", "optional": true }, { "name": "callback" } ] } ] }, { "textRaw": "zlib.deflateSync(buf[, options])", "type": "method", "name": "deflateSync", "desc": "Compress a Buffer or string with Deflate.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.deflateRaw(buf[, options], callback)", "type": "method", "name": "deflateRaw", "desc": "Compress a Buffer or string with DeflateRaw.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] }, { "params": [ { "name": "buf" }, { "name": "options", "optional": true }, { "name": "callback" } ] } ] }, { "textRaw": "zlib.deflateRawSync(buf[, options])", "type": "method", "name": "deflateRawSync", "desc": "Compress a Buffer or string with DeflateRaw.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.gunzip(buf[, options], callback)", "type": "method", "name": "gunzip", "desc": "Decompress a Buffer or string with Gunzip.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] }, { "params": [ { "name": "buf" }, { "name": "options", "optional": true }, { "name": "callback" } ] } ] }, { "textRaw": "zlib.gunzipSync(buf[, options])", "type": "method", "name": "gunzipSync", "desc": "Decompress a Buffer or string with Gunzip.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.gzip(buf[, options], callback)", "type": "method", "name": "gzip", "desc": "Compress a Buffer or string with Gzip.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] }, { "params": [ { "name": "buf" }, { "name": "options", "optional": true }, { "name": "callback" } ] } ] }, { "textRaw": "zlib.gzipSync(buf[, options])", "type": "method", "name": "gzipSync", "desc": "Compress a Buffer or string with Gzip.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.inflate(buf[, options], callback)", "type": "method", "name": "inflate", "desc": "Decompress a Buffer or string with Inflate.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] }, { "params": [ { "name": "buf" }, { "name": "options", "optional": true }, { "name": "callback" } ] } ] }, { "textRaw": "zlib.inflateSync(buf[, options])", "type": "method", "name": "inflateSync", "desc": "Decompress a Buffer or string with Inflate.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.inflateRaw(buf[, options], callback)", "type": "method", "name": "inflateRaw", "desc": "Decompress a Buffer or string with InflateRaw.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] }, { "params": [ { "name": "buf" }, { "name": "options", "optional": true }, { "name": "callback" } ] } ] }, { "textRaw": "zlib.inflateRawSync(buf[, options])", "type": "method", "name": "inflateRawSync", "desc": "Decompress a Buffer or string with InflateRaw.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.unzip(buf[, options], callback)", "type": "method", "name": "unzip", "desc": "Decompress a Buffer or string with Unzip.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] }, { "params": [ { "name": "buf" }, { "name": "options", "optional": true }, { "name": "callback" } ] } ] }, { "textRaw": "zlib.unzipSync(buf[, options])", "type": "method", "name": "unzipSync", "desc": "Decompress a Buffer or string with Unzip.\n\n
\n", "signatures": [ { "params": [ { "name": "buf" }, { "name": "options", "optional": true } ] } ] } ] } ], "modules": [ { "textRaw": "Flushing", "name": "flushing", "desc": "Calling [.flush()
][] on a compression stream will make zlib return as much\noutput as currently possible. This may come at the cost of degraded compression\nquality, but can be useful when data needs to be available as soon as possible.\n\n
In the following example, flush()
is used to write a compressed partial\nHTTP response to the client:\n
const zlib = require('zlib');\nconst http = require('http');\n\nhttp.createServer((request, response) => {\n // For the sake of simplicity, the Accept-Encoding checks are omitted.\n response.writeHead(200, { 'content-encoding': 'gzip' });\n const output = zlib.createGzip();\n output.pipe(response);\n\n setInterval(() => {\n output.write(`The current time is ${Date()}\\n`, () => {\n // The data has been passed to zlib, but the compression algorithm may\n // have decided to buffer the data for more efficient compression.\n // Calling .flush() will make the data available as soon as the client\n // is ready to receive it.\n output.flush();\n });\n }, 1000);\n}).listen(1337);
\n",
"type": "module",
"displayName": "Flushing"
}
],
"classes": [
{
"textRaw": "Class: zlib.Deflate",
"type": "class",
"name": "zlib.Deflate",
"desc": "Compress data using deflate.\n\n
\n" }, { "textRaw": "Class: zlib.DeflateRaw", "type": "class", "name": "zlib.DeflateRaw", "desc": "Compress data using deflate, and do not append a zlib header.\n\n
\n" }, { "textRaw": "Class: zlib.Gunzip", "type": "class", "name": "zlib.Gunzip", "desc": "Decompress a gzip stream.\n\n
\n" }, { "textRaw": "Class: zlib.Gzip", "type": "class", "name": "zlib.Gzip", "desc": "Compress data using gzip.\n\n
\n" }, { "textRaw": "Class: zlib.Inflate", "type": "class", "name": "zlib.Inflate", "desc": "Decompress a deflate stream.\n\n
\n" }, { "textRaw": "Class: zlib.InflateRaw", "type": "class", "name": "zlib.InflateRaw", "desc": "Decompress a raw deflate stream.\n\n
\n" }, { "textRaw": "Class: zlib.Unzip", "type": "class", "name": "zlib.Unzip", "desc": "Decompress either a Gzip- or Deflate-compressed stream by auto-detecting\nthe header.\n\n
\n" }, { "textRaw": "Class: zlib.Zlib", "type": "class", "name": "zlib.Zlib", "desc": "Not exported by the zlib
module. It is documented here because it is the base\nclass of the compressor/decompressor classes.\n\n
kind
defaults to zlib.Z_FULL_FLUSH
.\n\n
Flush pending data. Don't call this frivolously, premature flushes negatively\nimpact the effectiveness of the compression algorithm.\n\n
\nCalling this only flushes data from the internal zlib state, and does not\nperform flushing of any kind on the streams level. Rather, it behaves like a\nnormal call to .write()
, i.e. it will be queued up behind other pending\nwrites and will only produce output when data is being read from the stream.\n\n
Dynamically update the compression level and compression strategy.\nOnly applicable to deflate algorithm.\n\n
\n", "signatures": [ { "params": [ { "name": "level" }, { "name": "strategy" }, { "name": "callback" } ] } ] }, { "textRaw": "zlib.reset()", "type": "method", "name": "reset", "desc": "Reset the compressor/decompressor to factory defaults. Only applicable to\nthe inflate and deflate algorithms.\n\n
\n", "signatures": [ { "params": [] } ] } ] } ], "methods": [ { "textRaw": "zlib.createDeflate([options])", "type": "method", "name": "createDeflate", "desc": "Returns a new [Deflate][] object with an [options][].\n\n
\n", "signatures": [ { "params": [ { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.createDeflateRaw([options])", "type": "method", "name": "createDeflateRaw", "desc": "Returns a new [DeflateRaw][] object with an [options][].\n\n
\n", "signatures": [ { "params": [ { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.createGunzip([options])", "type": "method", "name": "createGunzip", "desc": "Returns a new [Gunzip][] object with an [options][].\n\n
\n", "signatures": [ { "params": [ { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.createGzip([options])", "type": "method", "name": "createGzip", "desc": "Returns a new [Gzip][] object with an [options][].\n\n
\n", "signatures": [ { "params": [ { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.createInflate([options])", "type": "method", "name": "createInflate", "desc": "Returns a new [Inflate][] object with an [options][].\n\n
\n", "signatures": [ { "params": [ { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.createInflateRaw([options])", "type": "method", "name": "createInflateRaw", "desc": "Returns a new [InflateRaw][] object with an [options][].\n\n
\n", "signatures": [ { "params": [ { "name": "options", "optional": true } ] } ] }, { "textRaw": "zlib.createUnzip([options])", "type": "method", "name": "createUnzip", "desc": "Returns a new [Unzip][] object with an [options][].\n\n
\n", "signatures": [ { "params": [ { "name": "options", "optional": true } ] } ] } ], "type": "module", "displayName": "Zlib" } ], "stability": 2, "stabilityText": "Stable", "classes": [ { "textRaw": "Class: Error", "type": "class", "name": "Error", "desc": "A generic JavaScript Error
object that does not denote any specific\ncircumstance of why the error occurred. Error
objects capture a "stack trace"\ndetailing the point in the code at which the Error
was instantiated, and may\nprovide a text description of the error.\n\n
All errors generated by Node.js, including all System and JavaScript errors,\nwill either be instances of, or inherit from, the Error
class.\n\n
Creates a .stack
property on targetObject
, which when accessed returns\na string representing the location in the code at which\nError.captureStackTrace()
was called.\n\n
const myObject = {};\nError.captureStackTrace(myObject);\nmyObject.stack // similar to `new Error().stack`
\nThe first line of the trace, instead of being prefixed with ErrorType:\nmessage
, will be the result of calling targetObject.toString()
.\n\n
The optional constructorOpt
argument accepts a function. If given, all frames\nabove constructorOpt
, including constructorOpt
, will be omitted from the\ngenerated stack trace.\n\n
The constructorOpt
argument is useful for hiding implementation\ndetails of error generation from an end user. For instance:\n\n
function MyError() {\n Error.captureStackTrace(this, MyError);\n}\n\n// Without passing MyError to captureStackTrace, the MyError\n// frame would should up in the .stack property. by passing\n// the constructor, we omit that frame and all frames above it.\nnew MyError().stack
\n",
"signatures": [
{
"params": [
{
"name": "targetObject"
},
{
"name": "constructorOpt",
"optional": true
}
]
}
]
}
],
"properties": [
{
"textRaw": "Error.stackTraceLimit",
"name": "stackTraceLimit",
"desc": "The Error.stackTraceLimit
property specifies the number of stack frames\ncollected by a stack trace (whether generated by new Error().stack
or\nError.captureStackTrace(obj)
).\n\n
The default value is 10
but may be set to any valid JavaScript number. Changes\nwill affect any stack trace captured after the value has been changed.\n\n
If set to a non-number value, or set to a negative number, stack traces will\nnot capture any frames.\n\n
\n", "properties": [ { "textRaw": "error.message", "name": "message", "desc": "Returns the string description of error as set by calling new Error(message)
.\nThe message
passed to the constructor will also appear in the first line of\nthe stack trace of the Error
, however changing this property after the\nError
object is created may not change the first line of the stack trace.\n\n
const err = new Error('The message');\nconsole.log(err.message);\n // Prints: The message
\n"
},
{
"textRaw": "error.stack",
"name": "stack",
"desc": "Returns a string describing the point in the code at which the Error
was\ninstantiated.\n\n
For example:\n\n
\nError: Things keep happening!\n at /home/gbusey/file.js:525:2\n at Frobnicator.refrobulate (/home/gbusey/business-logic.js:424:21)\n at Actor.<anonymous> (/home/gbusey/actors.js:400:8)\n at increaseSynergy (/home/gbusey/actors.js:701:6)
\nThe first line is formatted as <error class name>: <error message>
, and\nis followed by a series of stack frames (each line beginning with "at ").\nEach frame describes a call site within the code that lead to the error being\ngenerated. V8 attempts to display a name for each function (by variable name,\nfunction name, or object method name), but occasionally it will not be able to\nfind a suitable name. If V8 cannot determine a name for the function, only\nlocation information will be displayed for that frame. Otherwise, the\ndetermined function name will be displayed with location information appended\nin parentheses.\n\n
It is important to note that frames are only generated for JavaScript\nfunctions. If, for example, execution synchronously passes through a C++ addon\nfunction called cheetahify
, which itself calls a JavaScript function, the\nframe representing the cheetahify
call will not be present in the stack\ntraces:\n\n
const cheetahify = require('./native-binding.node');\n\nfunction makeFaster() {\n // cheetahify *synchronously* calls speedy.\n cheetahify(function speedy() {\n throw new Error('oh no!');\n });\n}\n\nmakeFaster(); // will throw:\n // /home/gbusey/file.js:6\n // throw new Error('oh no!');\n // ^\n // Error: oh no!\n // at speedy (/home/gbusey/file.js:6:11)\n // at makeFaster (/home/gbusey/file.js:5:3)\n // at Object.<anonymous> (/home/gbusey/file.js:10:1)\n // at Module._compile (module.js:456:26)\n // at Object.Module._extensions..js (module.js:474:10)\n // at Module.load (module.js:356:32)\n // at Function.Module._load (module.js:312:12)\n // at Function.Module.runMain (module.js:497:10)\n // at startup (node.js:119:16)\n // at node.js:906:3
\nThe location information will be one of:\n\n
\nnative
, if the frame represents a call internal to V8 (as in [].forEach
).plain-filename.js:line:column
, if the frame represents a call internal\n to Node.js./absolute/path/to/file.js:line:column
, if the frame represents a call in\na user program, or its dependencies.The string representing the stack trace is lazily generated when the\nerror.stack
property is accessed.\n\n
The number of frames captured by the stack trace is bounded by the smaller of\nError.stackTraceLimit
or the number of available frames on the current event\nloop tick.\n\n
System-level errors are generated as augmented Error
instances, which are\ndetailed here.\n\n
Creates a new Error
object and sets the error.message
property to the\nprovided text message. If an object is passed as message
, the text message\nis generated by calling message.toString()
. The error.stack
property will\nrepresent the point in the code at which new Error()
was called. Stack traces\nare dependent on [V8's stack trace API][]. Stack traces extend only to either\n(a) the beginning of synchronous code execution, or (b) the number of frames\ngiven by the property Error.stackTraceLimit
, whichever is smaller.\n\n
A subclass of Error
that indicates that a provided argument was not within the\nset or range of acceptable values for a function; whether that is a numeric\nrange, or outside the set of options for a given function parameter.\n\n
For example:\n\n
\nrequire('net').connect(-1);\n // throws RangeError, port should be > 0 && < 65536
\nNode.js will generate and throw RangeError
instances immediately as a form\nof argument validation.\n\n
A subclass of Error
that indicates that an attempt is being made to access a\nvariable that is not defined. Such errors commonly indicate typos in code, or\nan otherwise broken program.\n\n
While client code may generate and propagate these errors, in practice, only V8\nwill do so.\n\n
\ndoesNotExist;\n // throws ReferenceError, doesNotExist is not a variable in this program.
\nReferenceError
instances will have an error.arguments
property whose value\nis an array containing a single element: a string representing the variable\nthat was not defined.\n\n
const assert = require('assert');\ntry {\n doesNotExist;\n} catch(err) {\n assert(err.arguments[0], 'doesNotExist');\n}
\nUnless an application is dynamically generating and running code,\nReferenceError
instances should always be considered a bug in the code\nor its dependencies.\n\n
A subclass of Error
that indicates that a program is not valid JavaScript.\nThese errors may only be generated and propagated as a result of code\nevaluation. Code evaluation may happen as a result of eval
, Function
,\nrequire
, or [vm][]. These errors are almost always indicative of a broken\nprogram.\n\n
try {\n require('vm').runInThisContext('binary ! isNotOk');\n} catch(err) {\n // err will be a SyntaxError\n}
\nSyntaxError
instances are unrecoverable in the context that created them –\nthey may only be caught by other contexts.\n\n
A subclass of Error
that indicates that a provided argument is not an\nallowable type. For example, passing a function to a parameter which expects a\nstring would be considered a TypeError.\n\n
require('url').parse(() => { });\n // throws TypeError, since it expected a string
\nNode.js will generate and throw TypeError
instances immediately as a form\nof argument validation.\n\n
Used to handle binary data. See the [buffer section][].\n\n
\n" }, { "textRaw": "clearImmediate(immediateObject)", "type": "global", "name": "clearImmediate", "desc": "[clearImmediate
] is described in the [timers][] section.\n\n
[clearInterval
] is described in the [timers][] section.\n\n
[clearTimeout
] is described in the [timers][] section.\n\n
Used to print to stdout and stderr. See the [console
][] section.\n\n
In browsers, the top-level scope is the global scope. That means that in\nbrowsers if you're in the global scope var something
will define a global\nvariable. In Node.js this is different. The top-level scope is not the global\nscope; var something
inside an Node.js module will be local to that module.\n\n
The process object. See the [process
object][] section.\n\n
[setImmediate
] is described in the [timers][] section.\n\n
[setInterval
] is described in the [timers][] section.\n\n
[setTimeout
] is described in the [timers][] section.\n\n
The process
object is a global object and can be accessed from anywhere.\nIt is an instance of [EventEmitter
][].\n\n
This event is emitted when Node.js empties its event loop and has nothing else\nto schedule. Normally, Node.js exits when there is no work scheduled, but a\nlistener for 'beforeExit'
can make asynchronous calls, and cause Node.js to\ncontinue.\n\n
'beforeExit'
is not emitted for conditions causing explicit termination, such\nas [process.exit()
][] or uncaught exceptions, and should not be used as an\nalternative to the 'exit'
event unless the intention is to schedule more work.\n\n
If process is spawned with an IPC channel, 'disconnect'
will be emitted when\nIPC channel is closed. Read more in [child_process 'disconnect'
event][] doc.\n\n
Emitted when the process is about to exit. There is no way to prevent the\nexiting of the event loop at this point, and once all 'exit'
listeners have\nfinished running the process will exit. Therefore you must only perform\nsynchronous operations in this handler. This is a good hook to perform\nchecks on the module's state (like for unit tests). The callback takes one\nargument, the code the process is exiting with.\n\n
This event is only emitted when Node.js exits explicitly by process.exit() or\nimplicitly by the event loop draining.\n\n
\nExample of listening for 'exit'
:\n\n
process.on('exit', (code) => {\n // do *NOT* do this\n setTimeout(() => {\n console.log('This will not run');\n }, 0);\n console.log('About to exit with code:', code);\n});
\n",
"params": []
},
{
"textRaw": "Event: 'message'",
"type": "event",
"name": "message",
"params": [],
"desc": "Messages sent by [ChildProcess.send()
][] are obtained using the 'message'
\nevent on the child's process object.\n\n
Emitted whenever a Promise was rejected and an error handler was attached to it\n(for example with [promise.catch()
][]) later than after an event loop turn. This event\nis emitted with the following arguments:\n\n
p
the promise that was previously emitted in an 'unhandledRejection'
\nevent, but which has now gained a rejection handler.There is no notion of a top level for a promise chain at which rejections can\nalways be handled. Being inherently asynchronous in nature, a promise rejection\ncan be handled at a future point in time — possibly much later than the\nevent loop turn it takes for the 'unhandledRejection'
event to be emitted.\n\n
Another way of stating this is that, unlike in synchronous code where there is\nan ever-growing list of unhandled exceptions, with promises there is a\ngrowing-and-shrinking list of unhandled rejections. In synchronous code, the\n'uncaughtException'
event tells you when the list of unhandled exceptions\ngrows. And in asynchronous code, the 'unhandledRejection'
event tells you\nwhen the list of unhandled rejections grows, while the 'rejectionHandled'
\nevent tells you when the list of unhandled rejections shrinks.\n\n
For example using the rejection detection hooks in order to keep a map of all\nthe rejected promise reasons at a given time:\n\n
\nconst unhandledRejections = new Map();\nprocess.on('unhandledRejection', (reason, p) => {\n unhandledRejections.set(p, reason);\n});\nprocess.on('rejectionHandled', (p) => {\n unhandledRejections.delete(p);\n});
\nThis map will grow and shrink over time, reflecting rejections that start\nunhandled and then become handled. You could record the errors in some error\nlog, either periodically (probably best for long-running programs, allowing\nyou to clear the map, which in the case of a very buggy program could grow\nindefinitely) or upon process exit (more convenient for scripts).\n\n
\n", "params": [] }, { "textRaw": "Event: 'uncaughtException'", "type": "event", "name": "uncaughtException", "desc": "The 'uncaughtException'
event is emitted when an exception bubbles all the\nway back to the event loop. By default, Node.js handles such exceptions by\nprinting the stack trace to stderr and exiting. Adding a handler for the\n'uncaughtException'
event overrides this default behavior.\n\n
For example:\n\n
\nprocess.on('uncaughtException', (err) => {\n console.log(`Caught exception: ${err}`);\n});\n\nsetTimeout(() => {\n console.log('This will still run.');\n}, 500);\n\n// Intentionally cause an exception, but don't catch it.\nnonexistentFunc();\nconsole.log('This will not run.');
\n",
"modules": [
{
"textRaw": "Warning: Using `'uncaughtException'` correctly",
"name": "warning:_using_`'uncaughtexception'`_correctly",
"desc": "Note that 'uncaughtException'
is a crude mechanism for exception handling\nintended to be used only as a last resort. The event should not be used as\nan equivalent to On Error Resume Next
. Unhandled exceptions inherently mean\nthat an application is in an undefined state. Attempting to resume application\ncode without properly recovering from the exception can cause additional\nunforeseen and unpredictable issues.\n\n
Exceptions thrown from within the event handler will not be caught. Instead the\nprocess will exit with a non zero exit code and the stack trace will be printed.\nThis is to avoid infinite recursion.\n\n
\nAttempting to resume normally after an uncaught exception can be similar to\npulling out of the power cord when upgrading a computer -- nine out of ten\ntimes nothing happens - but the 10th time, the system becomes corrupted.\n\n
\nThe correct use of 'uncaughtException'
is to perform synchronous cleanup\nof allocated resources (e.g. file descriptors, handles, etc) before shutting\ndown the process. It is not safe to resume normal operation after\n'uncaughtException'
.\n\n
Emitted whenever a Promise
is rejected and no error handler is attached to\nthe promise within a turn of the event loop. When programming with promises\nexceptions are encapsulated as rejected promises. Such promises can be caught\nand handled using [promise.catch()
][] and rejections are propagated through\na promise chain. This event is useful for detecting and keeping track of\npromises that were rejected whose rejections were not handled yet. This event\nis emitted with the following arguments:\n\n
reason
the object with which the promise was rejected (usually an\n[Error
][] instance).p
the promise that was rejected.Here is an example that logs every unhandled rejection to the console\n\n
\nprocess.on('unhandledRejection', (reason, p) => {\n console.log("Unhandled Rejection at: Promise ", p, " reason: ", reason);\n // application specific logging, throwing an error, or other logic here\n});
\nFor example, here is a rejection that will trigger the 'unhandledRejection'
\nevent:\n\n
somePromise.then((res) => {\n return reportToUser(JSON.pasre(res)); // note the typo (`pasre`)\n}); // no `.catch` or `.then`
\nHere is an example of a coding pattern that will also trigger\n'unhandledRejection'
:\n\n
function SomeResource() {\n // Initially set the loaded status to a rejected promise\n this.loaded = Promise.reject(new Error('Resource not yet loaded!'));\n}\n\nvar resource = new SomeResource();\n// no .catch or .then on resource.loaded for at least a turn
\nIn cases like this, you may not want to track the rejection as a developer\nerror like you would for other 'unhandledRejection'
events. To address\nthis, you can either attach a dummy [.catch(() => { })
][promise.catch()
] handler to\nresource.loaded
, preventing the 'unhandledRejection'
event from being\nemitted, or you can use the ['rejectionHandled'
][] event.\n\n
Emitted whenever Node.js emits a process warning.\n\n
\nA process warning is similar to an error in that it describes exceptional\nconditions that are being brought to the user's attention. However, warnings\nare not part of the normal Node.js and JavaScript error handling flow.\nNode.js can emit warnings whenever it detects bad coding practices that could\nlead to sub-optimal application performance, bugs or security vulnerabilities.\n\n
\nThe event handler for 'warning'
events is called with a single warning
\nargument whose value is an Error
object. There are three key properties that\ndescribe the warning:\n\n
name
- The name of the warning (currently Warning
by default).message
- A system-provided description of the warning.stack
- A stack trace to the location in the code where the warning was\nissued.process.on('warning', (warning) => {\n console.warn(warning.name); // Print the warning name\n console.warn(warning.message); // Print the warning message\n console.warn(warning.stack); // Print the stack trace\n});
\nBy default, Node.js will print process warnings to stderr
. The --no-warnings
\ncommand-line option can be used to suppress the default console output but the\n'warning'
event will still be emitted by the process
object.\n\n
The following example illustrates the warning that is printed to stderr
when\ntoo many listeners have been added to an event\n\n
$ node\n> event.defaultMaxListeners = 1;\n> process.on('foo', () => {});\n> process.on('foo', () => {});\n> (node:38638) Warning: Possible EventEmitter memory leak detected. 2 foo\n... listeners added. Use emitter.setMaxListeners() to increase limit
\nIn contrast, the following example turns off the default warning output and\nadds a custom handler to the 'warning'
event:\n\n
$ node --no-warnings\n> var p = process.on('warning', (warning) => console.warn('Do not do that!'));\n> event.defaultMaxListeners = 1;\n> process.on('foo', () => {});\n> process.on('foo', () => {});\n> Do not do that!
\nThe --trace-warnings
command-line option can be used to have the default\nconsole output for warnings include the full stack trace of the warning.\n\n
The [process.emitWarning()
][process_emit_warning] method can be used to issue\ncustom or application specific warnings.\n\n
// Emit a warning using a string...\nprocess.emitWarning('Something happened!');\n // Prints: (node 12345) Warning: Something happened!\n\n// Emit a warning using an object...\nprocess.emitWarning('Something Happened!', 'CustomWarning');\n // Prints: (node 12345) CustomWarning: Something happened!\n\n// Emit a warning using a custom Error object...\nclass CustomWarning extends Error {\n constructor(message) {\n super(message);\n this.name = 'CustomWarning';\n Error.captureStackTrace(this, CustomWarning);\n }\n}\nconst myWarning = new CustomWarning('Something happened!');\nprocess.emitWarning(myWarning);\n // Prints: (node 12345) CustomWarning: Something happened!
\n",
"type": "module",
"displayName": "Emitting custom warnings"
},
{
"textRaw": "Emitting custom deprecation warnings",
"name": "emitting_custom_deprecation_warnings",
"desc": "Custom deprecation warnings can be emitted by setting the name
of a custom\nwarning to DeprecationWarning
. For instance:\n\n
process.emitWarning('This API is deprecated', 'DeprecationWarning');
\nOr,\n\n
\nconst err = new Error('This API is deprecated');\nerr.name = 'DeprecationWarning';\nprocess.emitWarning(err);
\nLaunching Node.js using the --throw-deprecation
command line flag will\ncause custom deprecation warnings to be thrown as exceptions.\n\n
Using the --trace-deprecation
command line flag will cause the custom\ndeprecation to be printed to stderr
along with the stack trace.\n\n
Using the --no-deprecation
command line flag will suppress all reporting\nof the custom deprecation.\n\n
The *-deprecation
command line flags only affect warnings that use the name\nDeprecationWarning
.\n\n
Emitted when the processes receives a signal. See sigaction(2) for a list of\nstandard POSIX signal names such as SIGINT
, SIGHUP
, etc.\n\n
Example of listening for SIGINT
:\n\n
// Start reading from stdin so we don't exit.\nprocess.stdin.resume();\n\nprocess.on('SIGINT', () => {\n console.log('Got SIGINT. Press Control-D to exit.');\n});
\nAn easy way to send the SIGINT
signal is with Control-C
in most terminal\nprograms.\n\n
Note:\n\n
\nSIGUSR1
is reserved by Node.js to start the debugger. It's possible to\ninstall a listener but that won't stop the debugger from starting.SIGTERM
and SIGINT
have default handlers on non-Windows platforms that\nresets the terminal mode before exiting with code 128 + signal number
. If\none of these signals has a listener installed, its default behavior will be\nremoved (Node.js will no longer exit).SIGPIPE
is ignored by default. It can have a listener installed.SIGHUP
is generated on Windows when the console window is closed, and on other\nplatforms under various similar conditions, see signal(7). It can have a\nlistener installed, however Node.js will be unconditionally terminated by\nWindows about 10 seconds later. On non-Windows platforms, the default\nbehavior of SIGHUP
is to terminate Node.js, but once a listener has been\ninstalled its default behavior will be removed.SIGTERM
is not supported on Windows, it can be listened on.SIGINT
from the terminal is supported on all platforms, and can usually be\ngenerated with CTRL+C
(though this may be configurable). It is not generated\nwhen terminal raw mode is enabled.SIGBREAK
is delivered on Windows when CTRL+BREAK
is pressed, on\nnon-Windows\nplatforms it can be listened on, but there is no way to send or generate it.SIGWINCH
is delivered when the console has been resized. On Windows, this\nwill only happen on write to the console when the cursor is being moved, or\nwhen a readable tty is used in raw mode.SIGKILL
cannot have a listener installed, it will unconditionally terminate\nNode.js on all platforms.SIGSTOP
cannot have a listener installed.Note that Windows does not support sending Signals, but Node.js offers some\nemulation with [process.kill()
][], and [ChildProcess.kill()
][]. Sending signal 0
\ncan be used to test for the existence of a process. Sending SIGINT
,\nSIGTERM
, and SIGKILL
cause the unconditional termination of the target\nprocess.\n\n
Node.js will normally exit with a 0
status code when no more async\noperations are pending. The following status codes are used in other\ncases:\n\n
1
Uncaught Fatal Exception - There was an uncaught exception,\nand it was not handled by a domain or an ['uncaughtException'
][] event\nhandler.2
- Unused (reserved by Bash for builtin misuse)3
Internal JavaScript Parse Error - The JavaScript source code\ninternal in Node.js's bootstrapping process caused a parse error. This\nis extremely rare, and generally can only happen during development\nof Node.js itself.4
Internal JavaScript Evaluation Failure - The JavaScript\nsource code internal in Node.js's bootstrapping process failed to\nreturn a function value when evaluated. This is extremely rare, and\ngenerally can only happen during development of Node.js itself.5
Fatal Error - There was a fatal unrecoverable error in V8.\nTypically a message will be printed to stderr with the prefix FATAL\nERROR
.6
Non-function Internal Exception Handler - There was an\nuncaught exception, but the internal fatal exception handler\nfunction was somehow set to a non-function, and could not be called.7
Internal Exception Handler Run-Time Failure - There was an\nuncaught exception, and the internal fatal exception handler\nfunction itself threw an error while attempting to handle it. This\ncan happen, for example, if a ['uncaughtException'
][] or\ndomain.on('error')
handler throws an error.8
- Unused. In previous versions of Node.js, exit code 8 sometimes\nindicated an uncaught exception.9
- Invalid Argument - Either an unknown option was specified,\nor an option requiring a value was provided without a value.10
Internal JavaScript Run-Time Failure - The JavaScript\nsource code internal in Node.js's bootstrapping process threw an error\nwhen the bootstrapping function was called. This is extremely rare,\nand generally can only happen during development of Node.js itself.12
Invalid Debug Argument - The --debug
and/or --debug-brk
\noptions were set, but an invalid port number was chosen.>128
Signal Exits - If Node.js receives a fatal signal such as\nSIGKILL
or SIGHUP
, then its exit code will be 128
plus the\nvalue of the signal code. This is a standard Unix practice, since\nexit codes are defined to be 7-bit integers, and signal exits set\nthe high-order bit, and then contain the value of the signal code.This causes Node.js to emit an abort. This will cause Node.js to exit and\ngenerate a core file.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "process.chdir(directory)", "type": "method", "name": "chdir", "desc": "Changes the current working directory of the process or throws an exception if that fails.\n\n
\nconsole.log(`Starting directory: ${process.cwd()}`);\ntry {\n process.chdir('/tmp');\n console.log(`New directory: ${process.cwd()}`);\n}\ncatch (err) {\n console.log(`chdir: ${err}`);\n}
\n",
"signatures": [
{
"params": [
{
"name": "directory"
}
]
}
]
},
{
"textRaw": "process.cpuUsage([previousValue])",
"type": "method",
"name": "cpuUsage",
"desc": "Returns the user and system CPU time usage of the current process, in an object\nwith properties user
and system
, whose values are microsecond values\n(millionth of a second). These values measure time spent in user and\nsystem code respectively, and may end up being greater than actual elapsed time\nif multiple CPU cores are performing work for this process.\n\n
The result of a previous call to process.cpuUsage()
can be passed as the\nargument to the function, to get a diff reading.\n\n
const startUsage = process.cpuUsage();\n// { user: 38579, system: 6986 }\n\n// spin the CPU for 500 milliseconds\nconst now = Date.now();\nwhile (Date.now() - now < 500);\n\nconsole.log(process.cpuUsage(startUsage));\n// { user: 514883, system: 11226 }
\n",
"signatures": [
{
"params": [
{
"name": "previousValue",
"optional": true
}
]
}
]
},
{
"textRaw": "process.cwd()",
"type": "method",
"name": "cwd",
"desc": "Returns the current working directory of the process.\n\n
\nconsole.log(`Current directory: ${process.cwd()}`);
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.disconnect()",
"type": "method",
"name": "disconnect",
"desc": "Close the IPC channel to the parent process, allowing this child to exit\ngracefully once there are no other connections keeping it alive.\n\n
\nIdentical to the parent process's [ChildProcess.disconnect()
][].\n\n
If Node.js was not spawned with an IPC channel, process.disconnect()
will be\nundefined.\n\n
The process.emitWarning()
method can be used to emit custom or application\nspecific process warnings. These can be listened for by adding a handler to the\n[process.on('warning')
][process_warning] event.\n\n
// Emit a warning using a string...\nprocess.emitWarning('Something happened!');\n // Emits: (node: 56338) Warning: Something happened!
\n// Emit a warning using a string and a name...\nprocess.emitWarning('Something Happened!', 'CustomWarning');\n // Emits: (node:56338) CustomWarning: Something Happened!
\nIn each of the previous examples, an Error
object is generated internally by\nprocess.emitWarning()
and passed through to the\n[process.on('warning')
][process_warning] event.\n\n
process.on('warning', (warning) => {\n console.warn(warning.name);\n console.warn(warning.message);\n console.warn(warning.stack);\n});
\nIf warning
is passed as an Error
object, it will be passed through to the\nprocess.on('warning')
event handler unmodified (and the optional name
\nand ctor
arguments will be ignored):\n\n
// Emit a warning using an Error object...\nconst myWarning = new Error('Warning! Something happened!');\nmyWarning.name = 'CustomWarning';\n\nprocess.emitWarning(myWarning);\n // Emits: (node:56338) CustomWarning: Warning! Something Happened!
\nA TypeError
is thrown if warning
is anything other than a string or Error
\nobject.\n\n
Note that while process warnings use Error
objects, the process warning\nmechanism is not a replacement for normal error handling mechanisms.\n\n
The following additional handling is implemented if the warning name
is\nDeprecationWarning
:\n\n
--throw-deprecation
command-line flag is used, the deprecation\nwarning is thrown as an exception rather than being emitted as an event.--no-deprecation
command-line flag is used, the deprecation\nwarning is suppressed.--trace-deprecation
command-line flag is used, the deprecation\nwarning is printed to stderr
along with the full stack trace.As a best practice, warnings should be emitted only once per process. To do\nso, it is recommended to place the emitWarning()
behind a simple boolean\nflag as illustrated in the example below:\n\n
var warned = false;\nfunction emitMyWarning() {\n if (!warned) {\n process.emitWarning('Only warn once!');\n warned = true;\n }\n}\nemitMyWarning();\n // Emits: (node: 56339) Warning: Only warn once!\nemitMyWarning();\n // Emits nothing
\n",
"type": "module",
"displayName": "Avoiding duplicate warnings"
}
]
},
{
"textRaw": "process.exit([code])",
"type": "method",
"name": "exit",
"signatures": [
{
"params": [
{
"textRaw": "`code` {Integer} The exit code. Defaults to `0`. ",
"name": "code",
"type": "Integer",
"desc": "The exit code. Defaults to `0`.",
"optional": true
}
]
},
{
"params": [
{
"name": "code",
"optional": true
}
]
}
],
"desc": "The process.exit()
method instructs Node.js to terminate the process as\nquickly as possible with the specified exit code
. If the code
is omitted, \nexit uses either the 'success' code 0
or the value of process.exitCode
if\nspecified.\n\n
To exit with a 'failure' code:\n\n
\nprocess.exit(1);
\nThe shell that executed Node.js should see the exit code as 1
.\n\n
It is important to note that calling process.exit()
will force the process to\nexit as quickly as possible even if there are still asynchronous operations \npending that have not yet completed fully, including I/O operations to\nprocess.stdout
and process.stderr
.\n\n
In most situations, it is not actually necessary to call process.exit()
\nexplicitly. The Node.js process will exit on it's own if there is no additional\nwork pending in the event loop. The process.exitCode
property can be set to\ntell the process which exit code to use when the process exits gracefully.\n\n
For instance, the following example illustrates a misuse of the \nprocess.exit()
method that could lead to data printed to stdout being \ntruncated and lost:\n\n
// This is an example of what *not* to do:\nif (someConditionNotMet()) {\n printUsageToStdout();\n process.exit(1);\n}
\nThe reason this is problematic is because writes to process.stdout
in Node.js\nare non-blocking and may occur over multiple ticks of the Node.js event loop.\nCalling process.exit()
, however, forces the process to exit before those\nadditional writes to stdout
can be performed.\n\n
Rather than calling process.exit()
directly, the code should set the\nprocess.exitCode
and allow the process to exit naturally by avoiding\nscheduling any additional work for the event loop:\n\n
// How to properly set the exit code while letting\n// the process exit gracefully.\nif (someConditionNotMet()) {\n printUsageToStdout();\n process.exitCode = 1;\n}
\nIf it is necessary to terminate the Node.js process due to an error condition,\nthrowing an uncaught error and allowing the process to terminate accordingly\nis safer than calling process.exit()
.\n\n
Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nGets the effective group identity of the process. (See getegid(2).)\nThis is the numerical group id, not the group name.\n\n
\nif (process.getegid) {\n console.log(`Current gid: ${process.getegid()}`);\n}
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.geteuid()",
"type": "method",
"name": "geteuid",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nGets the effective user identity of the process. (See geteuid(2).)\nThis is the numerical userid, not the username.\n\n
\nif (process.geteuid) {\n console.log(`Current uid: ${process.geteuid()}`);\n}
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.getgid()",
"type": "method",
"name": "getgid",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nGets the group identity of the process. (See getgid(2).)\nThis is the numerical group id, not the group name.\n\n
\nif (process.getgid) {\n console.log(`Current gid: ${process.getgid()}`);\n}
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.getgroups()",
"type": "method",
"name": "getgroups",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nReturns an array with the supplementary group IDs. POSIX leaves it unspecified\nif the effective group ID is included but Node.js ensures it always is.\n\n
\n", "signatures": [ { "params": [] } ] }, { "textRaw": "process.getuid()", "type": "method", "name": "getuid", "desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nGets the user identity of the process. (See getuid(2).)\nThis is the numerical userid, not the username.\n\n
\nif (process.getuid) {\n console.log(`Current uid: ${process.getuid()}`);\n}
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.hrtime()",
"type": "method",
"name": "hrtime",
"desc": "Returns the current high-resolution real time in a [seconds, nanoseconds]
\ntuple Array. It is relative to an arbitrary time in the past. It is not\nrelated to the time of day and therefore not subject to clock drift. The\nprimary use is for measuring performance between intervals.\n\n
You may pass in the result of a previous call to process.hrtime()
to get\na diff reading, useful for benchmarks and measuring intervals:\n\n
var time = process.hrtime();\n// [ 1800216, 25 ]\n\nsetTimeout(() => {\n var diff = process.hrtime(time);\n // [ 1, 552 ]\n\n console.log('benchmark took %d nanoseconds', diff[0] * 1e9 + diff[1]);\n // benchmark took 1000000527 nanoseconds\n}, 1000);
\n",
"signatures": [
{
"params": []
}
]
},
{
"textRaw": "process.initgroups(user, extra_group)",
"type": "method",
"name": "initgroups",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nReads /etc/group and initializes the group access list, using all groups of\nwhich the user is a member. This is a privileged operation, meaning you need\nto be root or have the CAP_SETGID
capability.\n\n
user
is a user name or user ID. extra_group
is a group name or group ID.\n\n
Some care needs to be taken when dropping privileges. Example:\n\n
\nconsole.log(process.getgroups()); // [ 0 ]\nprocess.initgroups('bnoordhuis', 1000); // switch user\nconsole.log(process.getgroups()); // [ 27, 30, 46, 1000, 0 ]\nprocess.setgid(1000); // drop root gid\nconsole.log(process.getgroups()); // [ 27, 30, 46, 1000 ]
\n",
"signatures": [
{
"params": [
{
"name": "user"
},
{
"name": "extra_group"
}
]
}
]
},
{
"textRaw": "process.kill(pid[, signal])",
"type": "method",
"name": "kill",
"desc": "Send a signal to a process. pid
is the process id and signal
is the\nstring describing the signal to send. Signal names are strings like\n'SIGINT'
or 'SIGHUP'
. If omitted, the signal will be 'SIGTERM'
.\nSee [Signal Events][] and kill(2) for more information.\n\n
Will throw an error if target does not exist, and as a special case, a signal\nof 0
can be used to test for the existence of a process. Windows platforms\nwill throw an error if the pid
is used to kill a process group.\n\n
Note that even though the name of this function is process.kill
, it is really\njust a signal sender, like the kill
system call. The signal sent may do\nsomething other than kill the target process.\n\n
Example of sending a signal to yourself:\n\n
\nprocess.on('SIGHUP', () => {\n console.log('Got SIGHUP signal.');\n});\n\nsetTimeout(() => {\n console.log('Exiting.');\n process.exit(0);\n}, 100);\n\nprocess.kill(process.pid, 'SIGHUP');
\nNote: When SIGUSR1 is received by Node.js it starts the debugger, see\n[Signal Events][].\n\n
\n", "signatures": [ { "params": [ { "name": "pid" }, { "name": "signal", "optional": true } ] } ] }, { "textRaw": "process.memoryUsage()", "type": "method", "name": "memoryUsage", "desc": "Returns an object describing the memory usage of the Node.js process\nmeasured in bytes.\n\n
\nconst util = require('util');\n\nconsole.log(util.inspect(process.memoryUsage()));
\nThis will generate:\n\n
\n{ rss: 4935680,\n heapTotal: 1826816,\n heapUsed: 650472 }
\nheapTotal
and heapUsed
refer to V8's memory usage.\n\n\n
Once the current event loop turn runs to completion, call the callback\nfunction.\n\n
\nThis is not a simple alias to [setTimeout(fn, 0)
][], it's much more\nefficient. It runs before any additional I/O events (including\ntimers) fire in subsequent ticks of the event loop.\n\n
console.log('start');\nprocess.nextTick(() => {\n console.log('nextTick callback');\n});\nconsole.log('scheduled');\n// Output:\n// start\n// scheduled\n// nextTick callback
\nThis is important in developing APIs where you want to give the user the\nchance to assign event handlers after an object has been constructed,\nbut before any I/O has occurred.\n\n
\nfunction MyThing(options) {\n this.setupOptions(options);\n\n process.nextTick(() => {\n this.startDoingStuff();\n });\n}\n\nvar thing = new MyThing();\nthing.getReadyForStuff();\n\n// thing.startDoingStuff() gets called now, not before.
\nIt is very important for APIs to be either 100% synchronous or 100%\nasynchronous. Consider this example:\n\n
\n// WARNING! DO NOT USE! BAD UNSAFE HAZARD!\nfunction maybeSync(arg, cb) {\n if (arg) {\n cb();\n return;\n }\n\n fs.stat('file', cb);\n}
\nThis API is hazardous. If you do this:\n\n
\nmaybeSync(true, () => {\n foo();\n});\nbar();
\nthen it's not clear whether foo()
or bar()
will be called first.\n\n
This approach is much better:\n\n
\nfunction definitelyAsync(arg, cb) {\n if (arg) {\n process.nextTick(cb);\n return;\n }\n\n fs.stat('file', cb);\n}
\nNote: the nextTick queue is completely drained on each pass of the\nevent loop before additional I/O is processed. As a result,\nrecursively setting nextTick callbacks will block any I/O from\nhappening, just like a while(true);
loop.\n\n
When Node.js is spawned with an IPC channel attached, it can send messages to its\nparent process using process.send()
. Each will be received as a\n['message'
][] event on the parent's [ChildProcess
][] object.\n\n
Note: this function uses [JSON.stringify()
][] internally to serialize the message
.\n\n
If Node.js was not spawned with an IPC channel, process.send()
will be undefined.\n\n
Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nSets the effective group identity of the process. (See setegid(2).)\nThis accepts either a numerical ID or a group name string. If a group name\nis specified, this method blocks while resolving it to a numerical ID.\n\n
\nif (process.getegid && process.setegid) {\n console.log(`Current gid: ${process.getegid()}`);\n try {\n process.setegid(501);\n console.log(`New gid: ${process.getegid()}`);\n }\n catch (err) {\n console.log(`Failed to set gid: ${err}`);\n }\n}
\n",
"signatures": [
{
"params": [
{
"name": "id"
}
]
}
]
},
{
"textRaw": "process.seteuid(id)",
"type": "method",
"name": "seteuid",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nSets the effective user identity of the process. (See seteuid(2).)\nThis accepts either a numerical ID or a username string. If a username\nis specified, this method blocks while resolving it to a numerical ID.\n\n
\nif (process.geteuid && process.seteuid) {\n console.log(`Current uid: ${process.geteuid()}`);\n try {\n process.seteuid(501);\n console.log(`New uid: ${process.geteuid()}`);\n }\n catch (err) {\n console.log(`Failed to set uid: ${err}`);\n }\n}
\n",
"signatures": [
{
"params": [
{
"name": "id"
}
]
}
]
},
{
"textRaw": "process.setgid(id)",
"type": "method",
"name": "setgid",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nSets the group identity of the process. (See setgid(2).) This accepts either\na numerical ID or a group name string. If a group name is specified, this method\nblocks while resolving it to a numerical ID.\n\n
\nif (process.getgid && process.setgid) {\n console.log(`Current gid: ${process.getgid()}`);\n try {\n process.setgid(501);\n console.log(`New gid: ${process.getgid()}`);\n }\n catch (err) {\n console.log(`Failed to set gid: ${err}`);\n }\n}
\n",
"signatures": [
{
"params": [
{
"name": "id"
}
]
}
]
},
{
"textRaw": "process.setgroups(groups)",
"type": "method",
"name": "setgroups",
"desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nSets the supplementary group IDs. This is a privileged operation, meaning you\nneed to be root or have the CAP_SETGID
capability.\n\n
The list can contain group IDs, group names or both.\n\n
\n", "signatures": [ { "params": [ { "name": "groups" } ] } ] }, { "textRaw": "process.setuid(id)", "type": "method", "name": "setuid", "desc": "Note: this function is only available on POSIX platforms (i.e. not Windows,\nAndroid)\n\n
\nSets the user identity of the process. (See setuid(2).) This accepts either\na numerical ID or a username string. If a username is specified, this method\nblocks while resolving it to a numerical ID.\n\n
\nif (process.getuid && process.setuid) {\n console.log(`Current uid: ${process.getuid()}`);\n try {\n process.setuid(501);\n console.log(`New uid: ${process.getuid()}`);\n }\n catch (err) {\n console.log(`Failed to set uid: ${err}`);\n }\n}
\n",
"signatures": [
{
"params": [
{
"name": "id"
}
]
}
]
},
{
"textRaw": "process.umask([mask])",
"type": "method",
"name": "umask",
"desc": "Sets or reads the process's file mode creation mask. Child processes inherit\nthe mask from the parent process. Returns the old mask if mask
argument is\ngiven, otherwise returns the current mask.\n\n
const newmask = 0o022;\nconst oldmask = process.umask(newmask);\nconsole.log(\n `Changed umask from ${oldmask.toString(8)} to ${newmask.toString(8)}`\n);
\n",
"signatures": [
{
"params": [
{
"name": "mask",
"optional": true
}
]
}
]
},
{
"textRaw": "process.uptime()",
"type": "method",
"name": "uptime",
"desc": "Number of seconds Node.js has been running.\n\n
\n", "signatures": [ { "params": [] } ] } ], "properties": [ { "textRaw": "process.arch", "name": "arch", "desc": "What processor architecture you're running on: 'arm'
, 'ia32'
, or 'x64'
.\n\n
console.log('This processor architecture is ' + process.arch);
\n"
},
{
"textRaw": "process.argv",
"name": "argv",
"desc": "An array containing the command line arguments. The first element will be\n'node', the second element will be the name of the JavaScript file. The\nnext elements will be any additional command line arguments.\n\n
\n// print process.argv\nprocess.argv.forEach((val, index, array) => {\n console.log(`${index}: ${val}`);\n});
\nThis will generate:\n\n
\n$ node process-2.js one two=three four\n0: node\n1: /Users/mjr/work/node/process-2.js\n2: one\n3: two=three\n4: four
\n"
},
{
"textRaw": "process.config",
"name": "config",
"desc": "An Object containing the JavaScript representation of the configure options\nthat were used to compile the current Node.js executable. This is the same as\nthe config.gypi
file that was produced when running the ./configure
script.\n\n
An example of the possible output looks like:\n\n
\n{\n target_defaults:\n { cflags: [],\n default_configuration: 'Release',\n defines: [],\n include_dirs: [],\n libraries: [] },\n variables:\n {\n host_arch: 'x64',\n node_install_npm: 'true',\n node_prefix: '',\n node_shared_cares: 'false',\n node_shared_http_parser: 'false',\n node_shared_libuv: 'false',\n node_shared_zlib: 'false',\n node_use_dtrace: 'false',\n node_use_openssl: 'true',\n node_shared_openssl: 'false',\n strict_aliasing: 'true',\n target_arch: 'x64',\n v8_use_snapshot: 'true'\n }\n}
\nNote: the process.config
property is not read-only and there are existing\nmodules in the ecosystem that are known to extend, modify, or entirely replace\nthe value of process.config
.\n\n
If process.connected
is false
, it is no longer possible to send messages.\n\n
An object containing the user environment. See environ(7).\n\n
\nAn example of this object looks like:\n\n
\n{ TERM: 'xterm-256color',\n SHELL: '/usr/local/bin/bash',\n USER: 'maciej',\n PATH: '~/.bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin',\n PWD: '/Users/maciej',\n EDITOR: 'vim',\n SHLVL: '1',\n HOME: '/Users/maciej',\n LOGNAME: 'maciej',\n _: '/usr/local/bin/node' }
\nYou can write to this object, but changes won't be reflected outside of your\nprocess. That means that the following won't work:\n\n
\n$ node -e 'process.env.foo = "bar"' && echo $foo
\nBut this will:\n\n
\nprocess.env.foo = 'bar';\nconsole.log(process.env.foo);
\nAssigning a property on process.env
will implicitly convert the value\nto a string.\n\n
Example:\n\n
\nprocess.env.test = null;\nconsole.log(process.env.test);\n// => 'null'\nprocess.env.test = undefined;\nconsole.log(process.env.test);\n// => 'undefined'
\nUse delete
to delete a property from process.env
.\n\n
Example:\n\n
\nprocess.env.TEST = 1;\ndelete process.env.TEST;\nconsole.log(process.env.TEST);\n// => undefined
\n"
},
{
"textRaw": "process.execArgv",
"name": "execArgv",
"desc": "This is the set of Node.js-specific command line options from the\nexecutable that started the process. These options do not show up in\n[process.argv
][], and do not include the Node.js executable, the name of\nthe script, or any options following the script name. These options\nare useful in order to spawn child processes with the same execution\nenvironment as the parent.\n\n
Example:\n\n
\n$ node --harmony script.js --version
\nresults in process.execArgv:\n\n
\n['--harmony']
\nand process.argv:\n\n
\n['/usr/local/bin/node', 'script.js', '--version']
\n"
},
{
"textRaw": "process.execPath",
"name": "execPath",
"desc": "This is the absolute pathname of the executable that started the process.\n\n
\nExample:\n\n
\n/usr/local/bin/node
\n"
},
{
"textRaw": "process.exitCode",
"name": "exitCode",
"desc": "A number which will be the process exit code, when the process either\nexits gracefully, or is exited via [process.exit()
][] without specifying\na code.\n\n
Specifying a code to [process.exit(code)
][process.exit()
] will override any \nprevious setting of process.exitCode
.\n\n\n
Alternate way to retrieve [require.main
][]. The difference is that if the main\nmodule changes at runtime, [require.main
][] might still refer to the original main\nmodule in modules that were required before the change occurred. Generally it's\nsafe to assume that the two refer to the same module.\n\n
As with [require.main
][], it will be undefined
if there was no entry script.\n\n
The PID of the process.\n\n
\nconsole.log(`This process is pid ${process.pid}`);
\n"
},
{
"textRaw": "process.platform",
"name": "platform",
"desc": "What platform you're running on:\n'darwin'
, 'freebsd'
, 'linux'
, 'sunos'
or 'win32'
\n\n
console.log(`This platform is ${process.platform}`);
\n"
},
{
"textRaw": "process.release",
"name": "release",
"desc": "An Object containing metadata related to the current release, including URLs\nfor the source tarball and headers-only tarball.\n\n
\nprocess.release
contains the following properties:\n\n
name
: a string with a value that will always be 'node'
for Node.js. For\nlegacy io.js releases, this will be 'io.js'
.sourceUrl
: a complete URL pointing to a .tar.gz file containing the\nsource of the current release.headersUrl
: a complete URL pointing to a .tar.gz file containing only\nthe header files for the current release. This file is significantly smaller\nthan the full source file and can be used for compiling add-ons against\nNode.js.libUrl
: a complete URL pointing to an node.lib file matching the\narchitecture and version of the current release. This file is used for\ncompiling add-ons against Node.js. This property is only present on Windows\nbuilds of Node.js and will be missing on all other platforms.e.g.\n\n
\n{ name: 'node',\n sourceUrl: 'https://nodejs.org/download/release/v4.0.0/node-v4.0.0.tar.gz',\n headersUrl: 'https://nodejs.org/download/release/v4.0.0/node-v4.0.0-headers.tar.gz',\n libUrl: 'https://nodejs.org/download/release/v4.0.0/win-x64/node.lib' }
\nIn custom builds from non-release versions of the source tree, only the\nname
property may be present. The additional properties should not be\nrelied upon to exist.\n\n
A writable stream to stderr (on fd 2
).\n\n
process.stderr
and process.stdout
are unlike other streams in Node.js in\nthat they cannot be closed ([end()
][] will throw), they never emit the ['finish'
][]\nevent and that writes can block when output is redirected to a file (although\ndisks are fast and operating systems normally employ write-back caching so it\nshould be a very rare occurrence indeed.)\n\n
A Readable Stream
for stdin (on fd 0
).\n\n
Example of opening standard input and listening for both events:\n\n
\nprocess.stdin.setEncoding('utf8');\n\nprocess.stdin.on('readable', () => {\n var chunk = process.stdin.read();\n if (chunk !== null) {\n process.stdout.write(`data: ${chunk}`);\n }\n});\n\nprocess.stdin.on('end', () => {\n process.stdout.write('end');\n});
\nAs a Stream, process.stdin
can also be used in "old" mode that is compatible\nwith scripts written for node.js prior to v0.10.\nFor more information see [Stream compatibility][].\n\n
In "old" Streams mode the stdin stream is paused by default, so one\nmust call process.stdin.resume()
to read from it. Note also that calling\nprocess.stdin.resume()
itself would switch stream to "old" mode.\n\n
If you are starting a new project you should prefer a more recent "new" Streams\nmode over "old" one.\n\n
\n" }, { "textRaw": "process.stdout", "name": "stdout", "desc": "A Writable Stream
to stdout
(on fd 1
).\n\n
For example, a console.log
equivalent could look like this:\n\n
console.log = (msg) => {\n process.stdout.write(`${msg}\\n`);\n};
\nprocess.stderr
and process.stdout
are unlike other streams in Node.js in\nthat they cannot be closed ([end()
][] will throw), they never emit the ['finish'
][]\nevent and that writes can block when output is redirected to a file (although\ndisks are fast and operating systems normally employ write-back caching so it\nshould be a very rare occurrence indeed.)\n\n
To check if Node.js is being run in a TTY context, read the isTTY
property\non process.stderr
, process.stdout
, or process.stdin
:\n\n
$ node -p "Boolean(process.stdin.isTTY)"\ntrue\n$ echo "foo" | node -p "Boolean(process.stdin.isTTY)"\nfalse\n\n$ node -p "Boolean(process.stdout.isTTY)"\ntrue\n$ node -p "Boolean(process.stdout.isTTY)" | cat\nfalse
\nSee [the tty docs][] for more information.\n\n
\n" }, { "textRaw": "process.title", "name": "title", "desc": "Getter/setter to set what is displayed in ps
.\n\n
When used as a setter, the maximum length is platform-specific and probably\nshort.\n\n
\nOn Linux and OS X, it's limited to the size of the binary name plus the\nlength of the command line arguments because it overwrites the argv memory.\n\n
\nv0.8 allowed for longer process title strings by also overwriting the environ\nmemory but that was potentially insecure/confusing in some (rather obscure)\ncases.\n\n
\n" }, { "textRaw": "process.version", "name": "version", "desc": "A compiled-in property that exposes NODE_VERSION
.\n\n
console.log(`Version: ${process.version}`);
\n"
},
{
"textRaw": "process.versions",
"name": "versions",
"desc": "A property exposing version strings of Node.js and its dependencies.\n\n
\nconsole.log(process.versions);
\nWill print something like:\n\n
\n{ http_parser: '2.3.0',\n node: '1.1.1',\n v8: '4.1.0.14',\n uv: '1.3.0',\n zlib: '1.2.8',\n ares: '1.10.0-DEV',\n modules: '43',\n icu: '55.1',\n openssl: '1.0.1k' }
\n"
}
]
}
],
"vars": [
{
"textRaw": "\\_\\_dirname",
"name": "\\_\\_dirname",
"type": "var",
"desc": "The name of the directory that the currently executing script resides in.\n\n
\nExample: running node example.js
from /Users/mjr
\n\n
console.log(__dirname);\n// /Users/mjr
\n__dirname
isn't actually a global but rather local to each module.\n\n
For instance, given two modules: a
and b
, where b
is a dependency of\na
and there is a directory structure of:\n\n
/Users/mjr/app/a.js
/Users/mjr/app/node_modules/b/b.js
References to __dirname
within b.js
will return\n/Users/mjr/app/node_modules/b
while references to __dirname
within a.js
\nwill return /Users/mjr/app
.\n\n
The filename of the code being executed. This is the resolved absolute path\nof this code file. For a main program this is not necessarily the same\nfilename used in the command line. The value inside a module is the path\nto that module file.\n\n
\nExample: running node example.js
from /Users/mjr
\n\n
console.log(__filename);\n// /Users/mjr/example.js
\n__filename
isn't actually a global but rather local to each module.\n\n
A reference to the module.exports
that is shorter to type.\nSee [module system documentation][] for details on when to use exports
and\nwhen to use module.exports
.\n\n
exports
isn't actually a global but rather local to each module.\n\n
See the [module system documentation][] for more information.\n\n
\n" }, { "textRaw": "module", "name": "module", "type": "var", "desc": "A reference to the current module. In particular\nmodule.exports
is used for defining what a module exports and makes\navailable through require()
.\n\n
module
isn't actually a global but rather local to each module.\n\n
See the [module system documentation][] for more information.\n\n
\n" }, { "textRaw": "require()", "type": "var", "name": "require", "desc": "To require modules. See the [Modules][] section. require
isn't actually a\nglobal but rather local to each module.\n\n
Modules are cached in this object when they are required. By deleting a key\nvalue from this object, the next require
will reload the module. Note that\nthis does not apply to [native addons][], for which reloading will result in an\nError.\n\n
Instruct require
on how to handle certain file extensions.\n\n
Process files with the extension .sjs
as .js
:\n\n
require.extensions['.sjs'] = require.extensions['.js'];
\nDeprecated In the past, this list has been used to load\nnon-JavaScript modules into Node.js by compiling them on-demand.\nHowever, in practice, there are much better ways to do this, such as\nloading modules via some other Node.js program, or compiling them to\nJavaScript ahead of time.\n\n
\nSince the Module system is locked, this feature will probably never go\naway. However, it may have subtle bugs and complexities that are best\nleft untouched.\n\n
\n" } ], "methods": [ { "textRaw": "require.resolve()", "type": "method", "name": "resolve", "desc": "Use the internal require()
machinery to look up the location of a module,\nbut rather than loading the module, just return the resolved filename.\n\n