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Class: WritableBase

index.<internal>.WritableBase

The EventEmitter class is defined and exposed by the node:events module:

import { EventEmitter } from 'node:events';

All EventEmitters emit the event 'newListener' when new listeners are added and 'removeListener' when existing listeners are removed.

It supports the following option:

Since

v0.1.26

Hierarchy

Implements

Implemented by

Table of contents

Constructors

Properties

Methods

Constructors

constructor

new WritableBase(opts?): WritableBase

Parameters

Name Type
opts? WritableOptions

Returns

WritableBase

Overrides

Stream.constructor

Defined in

node_modules/@types/node/stream.d.ts:715

Properties

closed

Readonly closed: boolean

Is true after 'close' has been emitted.

Since

v18.0.0

Defined in

node_modules/@types/node/stream.d.ts:704


destroyed

destroyed: boolean

Is true after writable.destroy() has been called.

Since

v8.0.0

Defined in

node_modules/@types/node/stream.d.ts:699


errored

Readonly errored: null | Error

Returns error if the stream has been destroyed with an error.

Since

v18.0.0

Defined in

node_modules/@types/node/stream.d.ts:709


writable

Readonly writable: boolean

Is true if it is safe to call writable.write(), which means the stream has not been destroyed, errored, or ended.

Since

v11.4.0

Implementation of

WritableStream.writable

Defined in

node_modules/@types/node/stream.d.ts:660


writableCorked

Readonly writableCorked: number

Number of times writable.uncork() needs to be called in order to fully uncork the stream.

Since

v13.2.0, v12.16.0

Defined in

node_modules/@types/node/stream.d.ts:694


writableEnded

Readonly writableEnded: boolean

Is true after writable.end() has been called. This property does not indicate whether the data has been flushed, for this use writable.writableFinished instead.

Since

v12.9.0

Defined in

node_modules/@types/node/stream.d.ts:666


writableFinished

Readonly writableFinished: boolean

Is set to true immediately before the 'finish' event is emitted.

Since

v12.6.0

Defined in

node_modules/@types/node/stream.d.ts:671


writableHighWaterMark

Readonly writableHighWaterMark: number

Return the value of highWaterMark passed when creating this Writable.

Since

v9.3.0

Defined in

node_modules/@types/node/stream.d.ts:676


writableLength

Readonly writableLength: number

This property contains the number of bytes (or objects) in the queue ready to be written. The value provides introspection data regarding the status of the highWaterMark.

Since

v9.4.0

Defined in

node_modules/@types/node/stream.d.ts:683


writableNeedDrain

Readonly writableNeedDrain: boolean

Is true if the stream's buffer has been full and stream will emit 'drain'.

Since

v15.2.0, v14.17.0

Defined in

node_modules/@types/node/stream.d.ts:714


writableObjectMode

Readonly writableObjectMode: boolean

Getter for the property objectMode of a given Writable stream.

Since

v12.3.0

Defined in

node_modules/@types/node/stream.d.ts:688


captureRejectionSymbol

Static Readonly captureRejectionSymbol: typeof captureRejectionSymbol

Value: Symbol.for('nodejs.rejection')

See how to write a custom rejection handler.

Since

v13.4.0, v12.16.0

Inherited from

Stream.captureRejectionSymbol

Defined in

node_modules/@types/node/events.d.ts:402


captureRejections

Static captureRejections: boolean

Value: boolean

Change the default captureRejections option on all new EventEmitter objects.

Since

v13.4.0, v12.16.0

Inherited from

Stream.captureRejections

Defined in

node_modules/@types/node/events.d.ts:409


defaultMaxListeners

Static defaultMaxListeners: number

By default, a maximum of 10 listeners can be registered for any single event. This limit can be changed for individual EventEmitter instances using the emitter.setMaxListeners(n) method. To change the default for allEventEmitter instances, the events.defaultMaxListenersproperty can be used. If this value is not a positive number, a RangeErroris thrown.

Take caution when setting the events.defaultMaxListeners because the change affects allEventEmitter instances, including those created before the change is made. However, calling emitter.setMaxListeners(n) still has precedence over events.defaultMaxListeners.

This is not a hard limit. The EventEmitter instance will allow more listeners to be added but will output a trace warning to stderr indicating that a "possible EventEmitter memory leak" has been detected. For any singleEventEmitter, the emitter.getMaxListeners() and emitter.setMaxListeners()methods can be used to temporarily avoid this warning:

import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.setMaxListeners(emitter.getMaxListeners() + 1);
emitter.once('event', () => {
  // do stuff
  emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));
});

The --trace-warnings command-line flag can be used to display the stack trace for such warnings.

The emitted warning can be inspected with process.on('warning') and will have the additional emitter, type, and count properties, referring to the event emitter instance, the event's name and the number of attached listeners, respectively. Its name property is set to 'MaxListenersExceededWarning'.

Since

v0.11.2

Inherited from

Stream.defaultMaxListeners

Defined in

node_modules/@types/node/events.d.ts:446


errorMonitor

Static Readonly errorMonitor: typeof errorMonitor

This symbol shall be used to install a listener for only monitoring 'error'events. Listeners installed using this symbol are called before the regular'error' listeners are called.

Installing a listener using this symbol does not change the behavior once an'error' event is emitted. Therefore, the process will still crash if no regular 'error' listener is installed.

Since

v13.6.0, v12.17.0

Inherited from

Stream.errorMonitor

Defined in

node_modules/@types/node/events.d.ts:395

Methods

[captureRejectionSymbol]

[captureRejectionSymbol](error, event, ...args): void

Parameters

Name Type
error Error
event string
...args any[]

Returns

void

Implementation of

WritableStream.[captureRejectionSymbol]

Inherited from

Stream.[captureRejectionSymbol]

Defined in

node_modules/@types/node/events.d.ts:112


_construct

_construct(callback): void

Parameters

Name Type
callback (error?: null | Error) => void

Returns

void

Defined in

node_modules/@types/node/stream.d.ts:724


_destroy

_destroy(error, callback): void

Parameters

Name Type
error null | Error
callback (error?: null | Error) => void

Returns

void

Defined in

node_modules/@types/node/stream.d.ts:725


_final

_final(callback): void

Parameters

Name Type
callback (error?: null | Error) => void

Returns

void

Defined in

node_modules/@types/node/stream.d.ts:726


_write

_write(chunk, encoding, callback): void

Parameters

Name Type
chunk any
encoding BufferEncoding
callback (error?: null | Error) => void

Returns

void

Defined in

node_modules/@types/node/stream.d.ts:716


_writev

_writev(chunks, callback): void

Parameters

Name Type
chunks { chunk: any ; encoding: BufferEncoding }[]
callback (error?: null | Error) => void

Returns

void

Defined in

node_modules/@types/node/stream.d.ts:717


addListener

addListener(event, listener): WritableBase

Event emitter The defined events on documents including:

  1. close
  2. drain
  3. error
  4. finish
  5. pipe
  6. unpipe

Parameters

Name Type
event "close"
listener () => void

Returns

WritableBase

Implementation of

WritableStream.addListener

Overrides

Stream.addListener

Defined in

node_modules/@types/node/stream.d.ts:892

addListener(event, listener): WritableBase

Parameters

Name Type
event "drain"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.addListener

Overrides

Stream.addListener

Defined in

node_modules/@types/node/stream.d.ts:893

addListener(event, listener): WritableBase

Parameters

Name Type
event "error"
listener (err: Error) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.addListener

Overrides

Stream.addListener

Defined in

node_modules/@types/node/stream.d.ts:894

addListener(event, listener): WritableBase

Parameters

Name Type
event "finish"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.addListener

Overrides

Stream.addListener

Defined in

node_modules/@types/node/stream.d.ts:895

addListener(event, listener): WritableBase

Parameters

Name Type
event "pipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.addListener

Overrides

Stream.addListener

Defined in

node_modules/@types/node/stream.d.ts:896

addListener(event, listener): WritableBase

Parameters

Name Type
event "unpipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.addListener

Overrides

Stream.addListener

Defined in

node_modules/@types/node/stream.d.ts:897

addListener(event, listener): WritableBase

Parameters

Name Type
event string | symbol
listener (...args: any[]) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.addListener

Overrides

Stream.addListener

Defined in

node_modules/@types/node/stream.d.ts:898


compose

compose<T>(stream, options?): T

Type parameters

Name Type
T extends ReadableStream

Parameters

Name Type
stream ComposeFnParam | T | Iterable<T> | AsyncIterable<T>
options? Object
options.signal AbortSignal

Returns

T

Inherited from

Stream.compose

Defined in

node_modules/@types/node/stream.d.ts:35


cork

cork(): void

The writable.cork() method forces all written data to be buffered in memory. The buffered data will be flushed when either the uncork or end methods are called.

The primary intent of writable.cork() is to accommodate a situation in which several small chunks are written to the stream in rapid succession. Instead of immediately forwarding them to the underlying destination, writable.cork()buffers all the chunks until writable.uncork() is called, which will pass them all to writable._writev(), if present. This prevents a head-of-line blocking situation where data is being buffered while waiting for the first small chunk to be processed. However, use of writable.cork() without implementingwritable._writev() may have an adverse effect on throughput.

See also: writable.uncork(), writable._writev().

Returns

void

Since

v0.11.2

Defined in

node_modules/@types/node/stream.d.ts:830


destroy

destroy(error?): WritableBase

Destroy the stream. Optionally emit an 'error' event, and emit a 'close'event (unless emitClose is set to false). After this call, the writable stream has ended and subsequent calls to write() or end() will result in an ERR_STREAM_DESTROYED error. This is a destructive and immediate way to destroy a stream. Previous calls towrite() may not have drained, and may trigger an ERR_STREAM_DESTROYED error. Use end() instead of destroy if data should flush before close, or wait for the 'drain' event before destroying the stream.

Once destroy() has been called any further calls will be a no-op and no further errors except from _destroy() may be emitted as 'error'.

Implementors should not override this method, but instead implement writable._destroy().

Parameters

Name Type Description
error? Error Optional, an error to emit with 'error' event.

Returns

WritableBase

Since

v8.0.0

Defined in

node_modules/@types/node/stream.d.ts:881


emit

emit(event): boolean

Synchronously calls each of the listeners registered for the event namedeventName, in the order they were registered, passing the supplied arguments to each.

Returns true if the event had listeners, false otherwise.

import { EventEmitter } from 'node:events';
const myEmitter = new EventEmitter();

// First listener
myEmitter.on('event', function firstListener() {
  console.log('Helloooo! first listener');
});
// Second listener
myEmitter.on('event', function secondListener(arg1, arg2) {
  console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
});
// Third listener
myEmitter.on('event', function thirdListener(...args) {
  const parameters = args.join(', ');
  console.log(`event with parameters ${parameters} in third listener`);
});

console.log(myEmitter.listeners('event'));

myEmitter.emit('event', 1, 2, 3, 4, 5);

// Prints:
// [
//   [Function: firstListener],
//   [Function: secondListener],
//   [Function: thirdListener]
// ]
// Helloooo! first listener
// event with parameters 1, 2 in second listener
// event with parameters 1, 2, 3, 4, 5 in third listener

Parameters

Name Type
event "close"

Returns

boolean

Since

v0.1.26

Implementation of

WritableStream.emit

Overrides

Stream.emit

Defined in

node_modules/@types/node/stream.d.ts:899

emit(event): boolean

Parameters

Name Type
event "drain"

Returns

boolean

Implementation of

NodeJS.WritableStream.emit

Overrides

Stream.emit

Defined in

node_modules/@types/node/stream.d.ts:900

emit(event, err): boolean

Parameters

Name Type
event "error"
err Error

Returns

boolean

Implementation of

NodeJS.WritableStream.emit

Overrides

Stream.emit

Defined in

node_modules/@types/node/stream.d.ts:901

emit(event): boolean

Parameters

Name Type
event "finish"

Returns

boolean

Implementation of

NodeJS.WritableStream.emit

Overrides

Stream.emit

Defined in

node_modules/@types/node/stream.d.ts:902

emit(event, src): boolean

Parameters

Name Type
event "pipe"
src Readable

Returns

boolean

Implementation of

NodeJS.WritableStream.emit

Overrides

Stream.emit

Defined in

node_modules/@types/node/stream.d.ts:903

emit(event, src): boolean

Parameters

Name Type
event "unpipe"
src Readable

Returns

boolean

Implementation of

NodeJS.WritableStream.emit

Overrides

Stream.emit

Defined in

node_modules/@types/node/stream.d.ts:904

emit(event, ...args): boolean

Parameters

Name Type
event string | symbol
...args any[]

Returns

boolean

Implementation of

NodeJS.WritableStream.emit

Overrides

Stream.emit

Defined in

node_modules/@types/node/stream.d.ts:905


end

end(cb?): WritableBase

Calling the writable.end() method signals that no more data will be written to the Writable. The optional chunk and encoding arguments allow one final additional chunk of data to be written immediately before closing the stream.

Calling the write method after calling end will raise an error.

// Write 'hello, ' and then end with 'world!'.
const fs = require('node:fs');
const file = fs.createWriteStream('example.txt');
file.write('hello, ');
file.end('world!');
// Writing more now is not allowed!

Parameters

Name Type
cb? () => void

Returns

WritableBase

Since

v0.9.4

Implementation of

WritableStream.end

Defined in

node_modules/@types/node/stream.d.ts:813

end(chunk, cb?): WritableBase

Parameters

Name Type
chunk any
cb? () => void

Returns

WritableBase

Implementation of

WritableStream.end

Defined in

node_modules/@types/node/stream.d.ts:814

end(chunk, encoding, cb?): WritableBase

Parameters

Name Type
chunk any
encoding BufferEncoding
cb? () => void

Returns

WritableBase

Implementation of

WritableStream.end

Defined in

node_modules/@types/node/stream.d.ts:815


eventNames

eventNames(): (string | symbol)[]

Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.

import { EventEmitter } from 'node:events';

const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});

const sym = Symbol('symbol');
myEE.on(sym, () => {});

console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]

Returns

(string | symbol)[]

Since

v6.0.0

Implementation of

WritableStream.eventNames

Inherited from

Stream.eventNames

Defined in

node_modules/@types/node/events.d.ts:870


getMaxListeners

getMaxListeners(): number

Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to defaultMaxListeners.

Returns

number

Since

v1.0.0

Implementation of

WritableStream.getMaxListeners

Inherited from

Stream.getMaxListeners

Defined in

node_modules/@types/node/events.d.ts:722


listenerCount

listenerCount(eventName, listener?): number

Returns the number of listeners listening for the event named eventName. If listener is provided, it will return how many times the listener is found in the list of the listeners of the event.

Parameters

Name Type Description
eventName string | symbol The name of the event being listened for
listener? Function The event handler function

Returns

number

Since

v3.2.0

Implementation of

WritableStream.listenerCount

Inherited from

Stream.listenerCount

Defined in

node_modules/@types/node/events.d.ts:816


listeners

listeners(eventName): Function[]

Returns a copy of the array of listeners for the event named eventName.

server.on('connection', (stream) => {
  console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]

Parameters

Name Type
eventName string | symbol

Returns

Function[]

Since

v0.1.26

Implementation of

WritableStream.listeners

Inherited from

Stream.listeners

Defined in

node_modules/@types/node/events.d.ts:735


off

off(eventName, listener): WritableBase

Alias for emitter.removeListener().

Parameters

Name Type
eventName string | symbol
listener (...args: any[]) => void

Returns

WritableBase

Since

v10.0.0

Implementation of

WritableStream.off

Inherited from

Stream.off

Defined in

node_modules/@types/node/events.d.ts:695


on

on(event, listener): WritableBase

Adds the listener function to the end of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple times.

server.on('connection', (stream) => {
  console.log('someone connected!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. Theemitter.prependListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
//   b
//   a

Parameters

Name Type Description
event "close" The name of the event.
listener () => void The callback function

Returns

WritableBase

Since

v0.1.101

Implementation of

WritableStream.on

Overrides

Stream.on

Defined in

node_modules/@types/node/stream.d.ts:906

on(event, listener): WritableBase

Parameters

Name Type
event "drain"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.on

Overrides

Stream.on

Defined in

node_modules/@types/node/stream.d.ts:907

on(event, listener): WritableBase

Parameters

Name Type
event "error"
listener (err: Error) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.on

Overrides

Stream.on

Defined in

node_modules/@types/node/stream.d.ts:908

on(event, listener): WritableBase

Parameters

Name Type
event "finish"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.on

Overrides

Stream.on

Defined in

node_modules/@types/node/stream.d.ts:909

on(event, listener): WritableBase

Parameters

Name Type
event "pipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.on

Overrides

Stream.on

Defined in

node_modules/@types/node/stream.d.ts:910

on(event, listener): WritableBase

Parameters

Name Type
event "unpipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.on

Overrides

Stream.on

Defined in

node_modules/@types/node/stream.d.ts:911

on(event, listener): WritableBase

Parameters

Name Type
event string | symbol
listener (...args: any[]) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.on

Overrides

Stream.on

Defined in

node_modules/@types/node/stream.d.ts:912


once

once(event, listener): WritableBase

Adds a one-timelistener function for the event named eventName. The next time eventName is triggered, this listener is removed and then invoked.

server.once('connection', (stream) => {
  console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

By default, event listeners are invoked in the order they are added. Theemitter.prependOnceListener() method can be used as an alternative to add the event listener to the beginning of the listeners array.

import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
//   b
//   a

Parameters

Name Type Description
event "close" The name of the event.
listener () => void The callback function

Returns

WritableBase

Since

v0.3.0

Implementation of

WritableStream.once

Overrides

Stream.once

Defined in

node_modules/@types/node/stream.d.ts:913

once(event, listener): WritableBase

Parameters

Name Type
event "drain"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.once

Overrides

Stream.once

Defined in

node_modules/@types/node/stream.d.ts:914

once(event, listener): WritableBase

Parameters

Name Type
event "error"
listener (err: Error) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.once

Overrides

Stream.once

Defined in

node_modules/@types/node/stream.d.ts:915

once(event, listener): WritableBase

Parameters

Name Type
event "finish"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.once

Overrides

Stream.once

Defined in

node_modules/@types/node/stream.d.ts:916

once(event, listener): WritableBase

Parameters

Name Type
event "pipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.once

Overrides

Stream.once

Defined in

node_modules/@types/node/stream.d.ts:917

once(event, listener): WritableBase

Parameters

Name Type
event "unpipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.once

Overrides

Stream.once

Defined in

node_modules/@types/node/stream.d.ts:918

once(event, listener): WritableBase

Parameters

Name Type
event string | symbol
listener (...args: any[]) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.once

Overrides

Stream.once

Defined in

node_modules/@types/node/stream.d.ts:919


pipe

pipe<T>(destination, options?): T

Type parameters

Name Type
T extends WritableStream

Parameters

Name Type
destination T
options? Object
options.end? boolean

Returns

T

Inherited from

Stream.pipe

Defined in

node_modules/@types/node/stream.d.ts:29


prependListener

prependListener(event, listener): WritableBase

Adds the listener function to the beginning of the listeners array for the event named eventName. No checks are made to see if the listener has already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple times.

server.prependListener('connection', (stream) => {
  console.log('someone connected!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

Name Type Description
event "close" The name of the event.
listener () => void The callback function

Returns

WritableBase

Since

v6.0.0

Implementation of

WritableStream.prependListener

Overrides

Stream.prependListener

Defined in

node_modules/@types/node/stream.d.ts:920

prependListener(event, listener): WritableBase

Parameters

Name Type
event "drain"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependListener

Overrides

Stream.prependListener

Defined in

node_modules/@types/node/stream.d.ts:921

prependListener(event, listener): WritableBase

Parameters

Name Type
event "error"
listener (err: Error) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependListener

Overrides

Stream.prependListener

Defined in

node_modules/@types/node/stream.d.ts:922

prependListener(event, listener): WritableBase

Parameters

Name Type
event "finish"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependListener

Overrides

Stream.prependListener

Defined in

node_modules/@types/node/stream.d.ts:923

prependListener(event, listener): WritableBase

Parameters

Name Type
event "pipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependListener

Overrides

Stream.prependListener

Defined in

node_modules/@types/node/stream.d.ts:924

prependListener(event, listener): WritableBase

Parameters

Name Type
event "unpipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependListener

Overrides

Stream.prependListener

Defined in

node_modules/@types/node/stream.d.ts:925

prependListener(event, listener): WritableBase

Parameters

Name Type
event string | symbol
listener (...args: any[]) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependListener

Overrides

Stream.prependListener

Defined in

node_modules/@types/node/stream.d.ts:926


prependOnceListener

prependOnceListener(event, listener): WritableBase

Adds a one-timelistener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this listener is removed, and then invoked.

server.prependOnceListener('connection', (stream) => {
  console.log('Ah, we have our first user!');
});

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

Name Type Description
event "close" The name of the event.
listener () => void The callback function

Returns

WritableBase

Since

v6.0.0

Implementation of

WritableStream.prependOnceListener

Overrides

Stream.prependOnceListener

Defined in

node_modules/@types/node/stream.d.ts:927

prependOnceListener(event, listener): WritableBase

Parameters

Name Type
event "drain"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependOnceListener

Overrides

Stream.prependOnceListener

Defined in

node_modules/@types/node/stream.d.ts:928

prependOnceListener(event, listener): WritableBase

Parameters

Name Type
event "error"
listener (err: Error) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependOnceListener

Overrides

Stream.prependOnceListener

Defined in

node_modules/@types/node/stream.d.ts:929

prependOnceListener(event, listener): WritableBase

Parameters

Name Type
event "finish"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependOnceListener

Overrides

Stream.prependOnceListener

Defined in

node_modules/@types/node/stream.d.ts:930

prependOnceListener(event, listener): WritableBase

Parameters

Name Type
event "pipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependOnceListener

Overrides

Stream.prependOnceListener

Defined in

node_modules/@types/node/stream.d.ts:931

prependOnceListener(event, listener): WritableBase

Parameters

Name Type
event "unpipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependOnceListener

Overrides

Stream.prependOnceListener

Defined in

node_modules/@types/node/stream.d.ts:932

prependOnceListener(event, listener): WritableBase

Parameters

Name Type
event string | symbol
listener (...args: any[]) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.prependOnceListener

Overrides

Stream.prependOnceListener

Defined in

node_modules/@types/node/stream.d.ts:933


rawListeners

rawListeners(eventName): Function[]

Returns a copy of the array of listeners for the event named eventName, including any wrappers (such as those created by .once()).

import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));

// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];

// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();

// Logs "log once" to the console and removes the listener
logFnWrapper();

emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');

// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');

Parameters

Name Type
eventName string | symbol

Returns

Function[]

Since

v9.4.0

Implementation of

WritableStream.rawListeners

Inherited from

Stream.rawListeners

Defined in

node_modules/@types/node/events.d.ts:766


removeAllListeners

removeAllListeners(event?): WritableBase

Removes all listeners, or those of the specified eventName.

It is bad practice to remove listeners added elsewhere in the code, particularly when the EventEmitter instance was created by some other component or module (e.g. sockets or file streams).

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

Name Type
event? string | symbol

Returns

WritableBase

Since

v0.1.26

Implementation of

WritableStream.removeAllListeners

Inherited from

Stream.removeAllListeners

Defined in

node_modules/@types/node/events.d.ts:706


removeListener

removeListener(event, listener): WritableBase

Removes the specified listener from the listener array for the event namedeventName.

const callback = (stream) => {
  console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);

removeListener() will remove, at most, one instance of a listener from the listener array. If any single listener has been added multiple times to the listener array for the specified eventName, then removeListener() must be called multiple times to remove each instance.

Once an event is emitted, all listeners attached to it at the time of emitting are called in order. This implies that anyremoveListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them fromemit() in progress. Subsequent events behave as expected.

import { EventEmitter } from 'node:events';
class MyEmitter extends EventEmitter {}
const myEmitter = new MyEmitter();

const callbackA = () => {
  console.log('A');
  myEmitter.removeListener('event', callbackB);
};

const callbackB = () => {
  console.log('B');
};

myEmitter.on('event', callbackA);

myEmitter.on('event', callbackB);

// callbackA removes listener callbackB but it will still be called.
// Internal listener array at time of emit [callbackA, callbackB]
myEmitter.emit('event');
// Prints:
//   A
//   B

// callbackB is now removed.
// Internal listener array [callbackA]
myEmitter.emit('event');
// Prints:
//   A

Because listeners are managed using an internal array, calling this will change the position indices of any listener registered after the listener being removed. This will not impact the order in which listeners are called, but it means that any copies of the listener array as returned by the emitter.listeners() method will need to be recreated.

When a single function has been added as a handler multiple times for a single event (as in the example below), removeListener() will remove the most recently added instance. In the example the once('ping')listener is removed:

import { EventEmitter } from 'node:events';
const ee = new EventEmitter();

function pong() {
  console.log('pong');
}

ee.on('ping', pong);
ee.once('ping', pong);
ee.removeListener('ping', pong);

ee.emit('ping');
ee.emit('ping');

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

Name Type
event "close"
listener () => void

Returns

WritableBase

Since

v0.1.26

Implementation of

WritableStream.removeListener

Overrides

Stream.removeListener

Defined in

node_modules/@types/node/stream.d.ts:934

removeListener(event, listener): WritableBase

Parameters

Name Type
event "drain"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.removeListener

Overrides

Stream.removeListener

Defined in

node_modules/@types/node/stream.d.ts:935

removeListener(event, listener): WritableBase

Parameters

Name Type
event "error"
listener (err: Error) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.removeListener

Overrides

Stream.removeListener

Defined in

node_modules/@types/node/stream.d.ts:936

removeListener(event, listener): WritableBase

Parameters

Name Type
event "finish"
listener () => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.removeListener

Overrides

Stream.removeListener

Defined in

node_modules/@types/node/stream.d.ts:937

removeListener(event, listener): WritableBase

Parameters

Name Type
event "pipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.removeListener

Overrides

Stream.removeListener

Defined in

node_modules/@types/node/stream.d.ts:938

removeListener(event, listener): WritableBase

Parameters

Name Type
event "unpipe"
listener (src: Readable) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.removeListener

Overrides

Stream.removeListener

Defined in

node_modules/@types/node/stream.d.ts:939

removeListener(event, listener): WritableBase

Parameters

Name Type
event string | symbol
listener (...args: any[]) => void

Returns

WritableBase

Implementation of

NodeJS.WritableStream.removeListener

Overrides

Stream.removeListener

Defined in

node_modules/@types/node/stream.d.ts:940


setDefaultEncoding

setDefaultEncoding(encoding): WritableBase

The writable.setDefaultEncoding() method sets the default encoding for a Writable stream.

Parameters

Name Type Description
encoding BufferEncoding The new default encoding

Returns

WritableBase

Since

v0.11.15

Defined in

node_modules/@types/node/stream.d.ts:790


setMaxListeners

setMaxListeners(n): WritableBase

By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set toInfinity (or 0) to indicate an unlimited number of listeners.

Returns a reference to the EventEmitter, so that calls can be chained.

Parameters

Name Type
n number

Returns

WritableBase

Since

v0.3.5

Implementation of

WritableStream.setMaxListeners

Inherited from

Stream.setMaxListeners

Defined in

node_modules/@types/node/events.d.ts:716


uncork

uncork(): void

The writable.uncork() method flushes all data buffered since cork was called.

When using writable.cork() and writable.uncork() to manage the buffering of writes to a stream, defer calls to writable.uncork() usingprocess.nextTick(). Doing so allows batching of allwritable.write() calls that occur within a given Node.js event loop phase.

stream.cork();
stream.write('some ');
stream.write('data ');
process.nextTick(() => stream.uncork());

If the writable.cork() method is called multiple times on a stream, the same number of calls to writable.uncork() must be called to flush the buffered data.

stream.cork();
stream.write('some ');
stream.cork();
stream.write('data ');
process.nextTick(() => {
  stream.uncork();
  // The data will not be flushed until uncork() is called a second time.
  stream.uncork();
});

See also: writable.cork().

Returns

void

Since

v0.11.2

Defined in

node_modules/@types/node/stream.d.ts:864


write

write(chunk, callback?): boolean

The writable.write() method writes some data to the stream, and calls the supplied callback once the data has been fully handled. If an error occurs, the callback will be called with the error as its first argument. The callback is called asynchronously and before 'error' is emitted.

The return value is true if the internal buffer is less than thehighWaterMark configured when the stream was created after admitting chunk. If false is returned, further attempts to write data to the stream should stop until the 'drain' event is emitted.

While a stream is not draining, calls to write() will buffer chunk, and return false. Once all currently buffered chunks are drained (accepted for delivery by the operating system), the 'drain' event will be emitted. Once write() returns false, do not write more chunks until the 'drain' event is emitted. While calling write() on a stream that is not draining is allowed, Node.js will buffer all written chunks until maximum memory usage occurs, at which point it will abort unconditionally. Even before it aborts, high memory usage will cause poor garbage collector performance and high RSS (which is not typically released back to the system, even after the memory is no longer required). Since TCP sockets may never drain if the remote peer does not read the data, writing a socket that is not draining may lead to a remotely exploitable vulnerability.

Writing data while the stream is not draining is particularly problematic for a Transform, because the Transform streams are paused by default until they are piped or a 'data' or 'readable' event handler is added.

If the data to be written can be generated or fetched on demand, it is recommended to encapsulate the logic into a Readable and use pipe. However, if calling write() is preferred, it is possible to respect backpressure and avoid memory issues using the 'drain' event:

function write(data, cb) {
  if (!stream.write(data)) {
    stream.once('drain', cb);
  } else {
    process.nextTick(cb);
  }
}

// Wait for cb to be called before doing any other write.
write('hello', () => {
  console.log('Write completed, do more writes now.');
});

A Writable stream in object mode will always ignore the encoding argument.

Parameters

Name Type Description
chunk any Optional data to write. For streams not operating in object mode, chunk must be a string, Buffer or Uint8Array. For object mode streams, chunk may be any JavaScript value other than null.
callback? (error: undefined | null | Error) => void Callback for when this chunk of data is flushed.

Returns

boolean

false if the stream wishes for the calling code to wait for the 'drain' event to be emitted before continuing to write additional data; otherwise true.

Since

v0.9.4

Implementation of

WritableStream.write

Defined in

node_modules/@types/node/stream.d.ts:783

write(chunk, encoding, callback?): boolean

Parameters

Name Type
chunk any
encoding BufferEncoding
callback? (error: undefined | null | Error) => void

Returns

boolean

Implementation of

WritableStream.write

Defined in

node_modules/@types/node/stream.d.ts:784


addAbortListener

addAbortListener(signal, resource): Disposable

Listens once to the abort event on the provided signal.

Listening to the abort event on abort signals is unsafe and may lead to resource leaks since another third party with the signal can call e.stopImmediatePropagation(). Unfortunately Node.js cannot change this since it would violate the web standard. Additionally, the original API makes it easy to forget to remove listeners.

This API allows safely using AbortSignals in Node.js APIs by solving these two issues by listening to the event such that stopImmediatePropagation does not prevent the listener from running.

Returns a disposable so that it may be unsubscribed from more easily.

import { addAbortListener } from 'node:events';

function example(signal) {
  let disposable;
  try {
    signal.addEventListener('abort', (e) => e.stopImmediatePropagation());
    disposable = addAbortListener(signal, (e) => {
      // Do something when signal is aborted.
    });
  } finally {
    disposable?.[Symbol.dispose]();
  }
}

Parameters

Name Type
signal AbortSignal
resource (event: Event) => void

Returns

Disposable

Disposable that removes the abort listener.

Since

v20.5.0

Inherited from

Stream.addAbortListener

Defined in

node_modules/@types/node/events.d.ts:387


getEventListeners

getEventListeners(emitter, name): Function[]

Returns a copy of the array of listeners for the event named eventName.

For EventEmitters this behaves exactly the same as calling .listeners on the emitter.

For EventTargets this is the only way to get the event listeners for the event target. This is useful for debugging and diagnostic purposes.

import { getEventListeners, EventEmitter } from 'node:events';

{
  const ee = new EventEmitter();
  const listener = () => console.log('Events are fun');
  ee.on('foo', listener);
  console.log(getEventListeners(ee, 'foo')); // [ [Function: listener] ]
}
{
  const et = new EventTarget();
  const listener = () => console.log('Events are fun');
  et.addEventListener('foo', listener);
  console.log(getEventListeners(et, 'foo')); // [ [Function: listener] ]
}

Parameters

Name Type
emitter EventEmitter | _DOMEventTarget
name string | symbol

Returns

Function[]

Since

v15.2.0, v14.17.0

Inherited from

Stream.getEventListeners

Defined in

node_modules/@types/node/events.d.ts:308


getMaxListeners

getMaxListeners(emitter): number

Returns the currently set max amount of listeners.

For EventEmitters this behaves exactly the same as calling .getMaxListeners on the emitter.

For EventTargets this is the only way to get the max event listeners for the event target. If the number of event handlers on a single EventTarget exceeds the max set, the EventTarget will print a warning.

import { getMaxListeners, setMaxListeners, EventEmitter } from 'node:events';

{
  const ee = new EventEmitter();
  console.log(getMaxListeners(ee)); // 10
  setMaxListeners(11, ee);
  console.log(getMaxListeners(ee)); // 11
}
{
  const et = new EventTarget();
  console.log(getMaxListeners(et)); // 10
  setMaxListeners(11, et);
  console.log(getMaxListeners(et)); // 11
}

Parameters

Name Type
emitter EventEmitter | _DOMEventTarget

Returns

number

Since

v19.9.0

Inherited from

Stream.getMaxListeners

Defined in

node_modules/@types/node/events.d.ts:337


listenerCount

listenerCount(emitter, eventName): number

A class method that returns the number of listeners for the given eventNameregistered on the given emitter.

import { EventEmitter, listenerCount } from 'node:events';

const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2

Parameters

Name Type Description
emitter EventEmitter The emitter to query
eventName string | symbol The event name

Returns

number

Since

v0.9.12

Deprecated

Since v3.2.0 - Use listenerCount instead.

Inherited from

Stream.listenerCount

Defined in

node_modules/@types/node/events.d.ts:280


on

on(emitter, eventName, options?): AsyncIterableIterator<any>

import { on, EventEmitter } from 'node:events';
import process from 'node:process';

const ee = new EventEmitter();

// Emit later on
process.nextTick(() => {
  ee.emit('foo', 'bar');
  ee.emit('foo', 42);
});

for await (const event of on(ee, 'foo')) {
  // The execution of this inner block is synchronous and it
  // processes one event at a time (even with await). Do not use
  // if concurrent execution is required.
  console.log(event); // prints ['bar'] [42]
}
// Unreachable here

Returns an AsyncIterator that iterates eventName events. It will throw if the EventEmitter emits 'error'. It removes all listeners when exiting the loop. The value returned by each iteration is an array composed of the emitted event arguments.

An AbortSignal can be used to cancel waiting on events:

import { on, EventEmitter } from 'node:events';
import process from 'node:process';

const ac = new AbortController();

(async () => {
  const ee = new EventEmitter();

  // Emit later on
  process.nextTick(() => {
    ee.emit('foo', 'bar');
    ee.emit('foo', 42);
  });

  for await (const event of on(ee, 'foo', { signal: ac.signal })) {
    // The execution of this inner block is synchronous and it
    // processes one event at a time (even with await). Do not use
    // if concurrent execution is required.
    console.log(event); // prints ['bar'] [42]
  }
  // Unreachable here
})();

process.nextTick(() => ac.abort());

Parameters

Name Type Description
emitter EventEmitter -
eventName string The name of the event being listened for
options? StaticEventEmitterOptions -

Returns

AsyncIterableIterator<any>

that iterates eventName events emitted by the emitter

Since

v13.6.0, v12.16.0

Inherited from

Stream.on

Defined in

node_modules/@types/node/events.d.ts:258


once

once(emitter, eventName, options?): Promise<any[]>

Creates a Promise that is fulfilled when the EventEmitter emits the given event or that is rejected if the EventEmitter emits 'error' while waiting. The Promise will resolve with an array of all the arguments emitted to the given event.

This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event semantics and does not listen to the 'error' event.

import { once, EventEmitter } from 'node:events';
import process from 'node:process';

const ee = new EventEmitter();

process.nextTick(() => {
  ee.emit('myevent', 42);
});

const [value] = await once(ee, 'myevent');
console.log(value);

const err = new Error('kaboom');
process.nextTick(() => {
  ee.emit('error', err);
});

try {
  await once(ee, 'myevent');
} catch (err) {
  console.error('error happened', err);
}

The special handling of the 'error' event is only used when events.once()is used to wait for another event. If events.once() is used to wait for the 'error' event itself, then it is treated as any other kind of event without special handling:

import { EventEmitter, once } from 'node:events';

const ee = new EventEmitter();

once(ee, 'error')
  .then(([err]) => console.log('ok', err.message))
  .catch((err) => console.error('error', err.message));

ee.emit('error', new Error('boom'));

// Prints: ok boom

An AbortSignal can be used to cancel waiting for the event:

import { EventEmitter, once } from 'node:events';

const ee = new EventEmitter();
const ac = new AbortController();

async function foo(emitter, event, signal) {
  try {
    await once(emitter, event, { signal });
    console.log('event emitted!');
  } catch (error) {
    if (error.name === 'AbortError') {
      console.error('Waiting for the event was canceled!');
    } else {
      console.error('There was an error', error.message);
    }
  }
}

foo(ee, 'foo', ac.signal);
ac.abort(); // Abort waiting for the event
ee.emit('foo'); // Prints: Waiting for the event was canceled!

Parameters

Name Type
emitter _NodeEventTarget
eventName string | symbol
options? StaticEventEmitterOptions

Returns

Promise<any[]>

Since

v11.13.0, v10.16.0

Inherited from

Stream.once

Defined in

node_modules/@types/node/events.d.ts:193

once(emitter, eventName, options?): Promise<any[]>

Parameters

Name Type
emitter _DOMEventTarget
eventName string
options? StaticEventEmitterOptions

Returns

Promise<any[]>

Inherited from

Stream.once

Defined in

node_modules/@types/node/events.d.ts:198


setMaxListeners

setMaxListeners(n?, ...eventTargets): void

import { setMaxListeners, EventEmitter } from 'node:events';

const target = new EventTarget();
const emitter = new EventEmitter();

setMaxListeners(5, target, emitter);

Parameters

Name Type Description
n? number A non-negative number. The maximum number of listeners per EventTarget event.
...eventTargets (EventEmitter | _DOMEventTarget)[] -

Returns

void

Since

v15.4.0

Inherited from

Stream.setMaxListeners

Defined in

node_modules/@types/node/events.d.ts:352

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