GunzipConditional

Class: GunzipConditional

Defined in: packages/utils/src/serializers.ts:135

Transform stream that transparently decompresses gzip data if the first chunk contains a gzip magic number (0x1f 0x8b), otherwise passes data through unchanged.

Extends

Transform

Constructors

Constructor

new GunzipConditional(options?): GunzipConditional

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1225

Parameters

options?

TransformOptions

Returns

GunzipConditional

Inherited from

Transform.constructor

Properties

allowHalfOpen

allowHalfOpen: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1142

If false then the stream will automatically end the writable side when the readable side ends. Set initially by the allowHalfOpen constructor option, which defaults to true.

This can be changed manually to change the half-open behavior of an existing Duplex stream instance, but must be changed before the 'end' event is emitted.

Since

v0.9.4

Inherited from

Transform.allowHalfOpen

closed

readonly closed: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:186

Is true after 'close' has been emitted.

Since

v18.0.0

Inherited from

Transform.closed

destroyed

destroyed: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:181

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

Since

v8.0.0

Inherited from

Transform.destroyed

errored

readonly errored: Error

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:191

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

Since

v18.0.0

Inherited from

Transform.errored

first

first: boolean = true

Defined in: packages/utils/src/serializers.ts:136

readable

readable: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:138

Is true if it is safe to call read, which means the stream has not been destroyed or emitted 'error' or 'end'.

Since

v11.4.0

Inherited from

Transform.readable

readableAborted

readonly readableAborted: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:132

Returns whether the stream was destroyed or errored before emitting 'end'.

Since

v16.8.0

Inherited from

Transform.readableAborted

readableDidRead

readonly readableDidRead: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:143

Returns whether 'data' has been emitted.

Since

v16.7.0, v14.18.0

Inherited from

Transform.readableDidRead

readableEncoding

readonly readableEncoding: BufferEncoding

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:148

Getter for the property encoding of a given Readable stream. The encoding property can be set using the setEncoding method.

Since

v12.7.0

Inherited from

Transform.readableEncoding

readableEnded

readonly readableEnded: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:153

Becomes true when 'end' event is emitted.

Since

v12.9.0

Inherited from

Transform.readableEnded

readableFlowing

readableFlowing: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:159

This property reflects the current state of a Readable stream as described in the Three states section.

Since

v9.4.0

Inherited from

Transform.readableFlowing

readableHighWaterMark

readonly readableHighWaterMark: number

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:164

Returns the value of highWaterMark passed when creating this Readable.

Since

v9.3.0

Inherited from

Transform.readableHighWaterMark

readableLength

readonly readableLength: number

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:171

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

Since

v9.4.0

Inherited from

Transform.readableLength

readableObjectMode

readonly readableObjectMode: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:176

Getter for the property objectMode of a given Readable stream.

Since

v12.3.0

Inherited from

Transform.readableObjectMode

writable

writable: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:779

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

Inherited from

Transform.writable

writableAborted

readonly writableAborted: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:784

Returns whether the stream was destroyed or errored before emitting 'finish'.

Since

v18.0.0, v16.17.0

Inherited from

Transform.writableAborted

writableCorked

readonly writableCorked: number

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:818

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

Since

v13.2.0, v12.16.0

Inherited from

Transform.writableCorked

writableEnded

readonly writableEnded: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:790

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

Inherited from

Transform.writableEnded

writableFinished

readonly writableFinished: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:795

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

Since

v12.6.0

Inherited from

Transform.writableFinished

writableHighWaterMark

readonly writableHighWaterMark: number

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:800

Return the value of highWaterMark passed when creating this Writable.

Since

v9.3.0

Inherited from

Transform.writableHighWaterMark

writableLength

readonly writableLength: number

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:807

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

Inherited from

Transform.writableLength

writableNeedDrain

readonly writableNeedDrain: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:838

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

Since

v15.2.0, v14.17.0

Inherited from

Transform.writableNeedDrain

writableObjectMode

readonly writableObjectMode: boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:812

Getter for the property objectMode of a given Writable stream.

Since

v12.3.0

Inherited from

Transform.writableObjectMode

zlib

zlib: Transform

Defined in: packages/utils/src/serializers.ts:137

Methods

_construct()?

optional _construct(callback): void

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:192

Parameters

callback

(error?) => void

Returns

void

Inherited from

Transform._construct

_destroy()

_destroy(error, callback): void

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:655

Parameters

error

Error

callback

(error?) => void

Returns

void

Inherited from

Transform._destroy

_final()

_final(callback): void

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:849

Parameters

callback

(error?) => void

Returns

void

Inherited from

Transform._final

_flush()

_flush(callback): void

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1227

Parameters

callback

TransformCallback

Returns

void

Inherited from

Transform._flush

_read()

_read(size): void

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:193

Parameters

size

number

Returns

void

Inherited from

Transform._read

_transform()

_transform(chunk, encoding, callback): void

Defined in: packages/utils/src/serializers.ts:146

Detect gzip on the first chunk and either decompress or pass through subsequent chunks.

Parameters

chunk

any

Incoming data chunk.

encoding

BufferEncoding

Encoding of the chunk.

callback

TransformCallback

Call when processing is complete.

Returns

void

Overrides

Transform._transform

_write()

_write(chunk, encoding, callback): void

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:839

Parameters

chunk

any

encoding

BufferEncoding

callback

(error?) => void

Returns

void

Inherited from

Transform._write

_writev()?

optional _writev(chunks, callback): void

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:840

Parameters

chunks

object[]

callback

(error?) => void

Returns

void

Inherited from

Transform._writev

[asyncDispose]()

[asyncDispose](): Promise<void>

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:678

Calls readable.destroy() with an AbortError and returns a promise that fulfills when the stream is finished.

Returns

Promise<void>

Since

v20.4.0

Inherited from

Transform.[asyncDispose]

[asyncIterator]()

[asyncIterator](): AsyncIterator<any>

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:672

Returns

AsyncIterator<any>

AsyncIterator to fully consume the stream.

Since

v10.0.0

Inherited from

Transform.[asyncIterator]

[captureRejectionSymbol]()?

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

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/events.d.ts:123

The Symbol.for('nodejs.rejection') method is called in case a promise rejection happens when emitting an event and captureRejections is enabled on the emitter. It is possible to use events.captureRejectionSymbol in place of Symbol.for('nodejs.rejection').

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

class MyClass extends EventEmitter {
  constructor() {
    super({ captureRejections: true });
  }

  [captureRejectionSymbol](err, event, ...args) {
    console.log('rejection happened for', event, 'with', err, ...args);
    this.destroy(err);
  }

  destroy(err) {
    // Tear the resource down here.
  }
}

Parameters

error

Error

event

string | symbol

args

...any[]

Returns

void

Since

v13.4.0, v12.16.0

Inherited from

Transform.[captureRejectionSymbol]

addListener()

Call Signature

addListener<E>(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1144

Alias for emitter.on(eventName, listener).

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName

E

listener

(...args) => void

Returns

this

Since

v0.1.26

Inherited from

Transform.addListener

Call Signature

addListener(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1148

Parameters

eventName

string | symbol

listener

(...args) => void

Returns

this

Inherited from

Transform.addListener

compose()

compose(stream, options?): Duplex

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:504

import { Readable } from 'node:stream';

async function* splitToWords(source) {
  for await (const chunk of source) {
    const words = String(chunk).split(' ');

    for (const word of words) {
      yield word;
    }
  }
}

const wordsStream = Readable.from(['text passed through', 'composed stream']).compose(splitToWords);
const words = await wordsStream.toArray();

console.log(words); // prints ['text', 'passed', 'through', 'composed', 'stream']

readable.compose(s) is equivalent to stream.compose(readable, s).

This method also allows for an AbortSignal to be provided, which will destroy the composed stream when aborted.

See stream.compose(...streams) for more information.

Parameters

stream

WritableStream | WritableStream<any> | TransformStream<any, any> | ((source) => void)

options?

Abortable

Returns

Duplex

a stream composed with the stream stream.

Since

v19.1.0, v18.13.0

Inherited from

Transform.compose

cork()

cork(): void

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:953

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 implementing writable._writev() may have an adverse effect on throughput.

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

Returns

void

Since

v0.11.2

Inherited from

Transform.cork

destroy()

destroy(error?): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:667

Destroy the stream. Optionally emit an 'error' event, and emit a 'close' event (unless emitClose is set to false). After this call, the readable stream will release any internal resources and subsequent calls to push() will be ignored.

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 readable._destroy().

Parameters

error?

Error

Error which will be passed as payload in 'error' event

Returns

this

Since

v8.0.0

Inherited from

Transform.destroy

drop()

drop(limit, options?): Readable

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:627

This method returns a new stream with the first limit chunks dropped from the start.

Parameters

limit

number

the number of chunks to drop from the readable.

options?

Abortable

Returns

Readable

a stream with limit chunks dropped from the start.

Since

v17.5.0

Inherited from

Transform.drop

emit()

Call Signature

emit<E>(eventName, ...args): boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1149

Synchronously calls each of the listeners registered for the event named eventName, 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

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName

E

args

...DuplexEventMap[E]

Returns

boolean

Since

v0.1.26

Inherited from

Transform.emit

Call Signature

emit(eventName, ...args): boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1150

Parameters

eventName

string | symbol

args

...any[]

Returns

boolean

Inherited from

Transform.emit

end()

end(...args): this

Defined in: packages/utils/src/serializers.ts:174

End the stream. If a gunzip transform is active, delegates to it; otherwise ends the base Transform.

Parameters

args

...any[]

Arguments forwarded to the underlying end() call.

Returns

this

Overrides

Transform.end

eventNames()

eventNames(): (string | symbol)[]

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/events.d.ts:190

Returns an array listing the events for which the emitter has registered listeners.

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

Inherited from

Transform.eventNames

every()

every(fn, options?): Promise<boolean>

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:603

This method is similar to Array.prototype.every and calls fn on each chunk in the stream to check if all awaited return values are truthy value for fn. Once an fn call on a chunk awaited return value is falsy, the stream is destroyed and the promise is fulfilled with false. If all of the fn calls on the chunks return a truthy value, the promise is fulfilled with true.

Parameters

fn

(data, options?) => boolean | Promise<boolean>

a function to call on each chunk of the stream. Async or not.

options?

Pick<ReadableOperatorOptions, "concurrency" | "signal">

Returns

Promise<boolean>

a promise evaluating to true if fn returned a truthy value for every one of the chunks.

Since

v17.5.0

Inherited from

Transform.every

filter()

filter(fn, options?): Readable

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:531

This method allows filtering the stream. For each chunk in the stream the fn function will be called and if it returns a truthy value, the chunk will be passed to the result stream. If the fn function returns a promise - that promise will be awaited.

Parameters

fn

(data, options?) => boolean | Promise<boolean>

a function to filter chunks from the stream. Async or not.

options?

ReadableOperatorOptions

Returns

Readable

a stream filtered with the predicate fn.

Since

v17.4.0, v16.14.0

Inherited from

Transform.filter

find()

Call Signature

find<T>(fn, options?): Promise<T>

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:586

This method is similar to Array.prototype.find and calls fn on each chunk in the stream to find a chunk with a truthy value for fn. Once an fn call's awaited return value is truthy, the stream is destroyed and the promise is fulfilled with value for which fn returned a truthy value. If all of the fn calls on the chunks return a falsy value, the promise is fulfilled with undefined.

Type Parameters

T

T

Parameters

fn

(data, options?) => data is T

a function to call on each chunk of the stream. Async or not.

options?

Pick<ReadableOperatorOptions, "concurrency" | "signal">

Returns

Promise<T>

a promise evaluating to the first chunk for which fn evaluated with a truthy value, or undefined if no element was found.

Since

v17.5.0

Inherited from

Transform.find

Call Signature

find(fn, options?): Promise<any>

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:590

Parameters

fn

(data, options?) => boolean | Promise<boolean>

a function to call on each chunk of the stream. Async or not.

options?

Pick<ReadableOperatorOptions, "concurrency" | "signal">

Returns

Promise<any>

a promise evaluating to the first chunk for which fn evaluated with a truthy value, or undefined if no element was found.

Since

v17.5.0

Inherited from

Transform.find

flatMap()

flatMap(fn, options?): Readable

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:617

This method returns a new stream by applying the given callback to each chunk of the stream and then flattening the result.

It is possible to return a stream or another iterable or async iterable from fn and the result streams will be merged (flattened) into the returned stream.

Parameters

fn

(data, options?) => any

a function to map over every chunk in the stream. May be async. May be a stream or generator.

options?

Pick<ReadableOperatorOptions, "concurrency" | "signal">

Returns

Readable

a stream flat-mapped with the function fn.

Since

v17.5.0

Inherited from

Transform.flatMap

forEach()

forEach(fn, options?): Promise<void>

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:550

This method allows iterating a stream. For each chunk in the stream the fn function will be called. If the fn function returns a promise - that promise will be awaited.

This method is different from for await...of loops in that it can optionally process chunks concurrently. In addition, a forEach iteration can only be stopped by having passed a signal option and aborting the related AbortController while for await...of can be stopped with break or return. In either case the stream will be destroyed.

This method is different from listening to the 'data' event in that it uses the readable event in the underlying machinary and can limit the number of concurrent fn calls.

Parameters

fn

(data, options?) => void | Promise<void>

a function to call on each chunk of the stream. Async or not.

options?

Pick<ReadableOperatorOptions, "concurrency" | "signal">

Returns

Promise<void>

a promise for when the stream has finished.

Since

v17.5.0

Inherited from

Transform.forEach

getMaxListeners()

getMaxListeners(): number

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/events.d.ts:197

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

Returns

number

Since

v1.0.0

Inherited from

Transform.getMaxListeners

isPaused()

isPaused(): boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:354

The readable.isPaused() method returns the current operating state of the Readable. This is used primarily by the mechanism that underlies the readable.pipe() method. In most typical cases, there will be no reason to use this method directly.

const readable = new stream.Readable();

readable.isPaused(); // === false
readable.pause();
readable.isPaused(); // === true
readable.resume();
readable.isPaused(); // === false

Returns

boolean

Since

v0.11.14

Inherited from

Transform.isPaused

iterator()

iterator(options?): AsyncIterator<any>

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:514

The iterator created by this method gives users the option to cancel the destruction of the stream if the for await...of loop is exited by return, break, or throw, or if the iterator should destroy the stream if the stream emitted an error during iteration.

Parameters

options?

ReadableIteratorOptions

Returns

AsyncIterator<any>

Since

v16.3.0

Inherited from

Transform.iterator

listenerCount()

Call Signature

listenerCount<E>(eventName, listener?): number

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1151

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.

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName

E

The name of the event being listened for

listener?

(...args) => void

The event handler function

Returns

number

Since

v3.2.0

Inherited from

Transform.listenerCount

Call Signature

listenerCount(eventName, listener?): number

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1155

Parameters

eventName

string | symbol

listener?

(...args) => void

Returns

number

Inherited from

Transform.listenerCount

listeners()

Call Signature

listeners<E>(eventName): (...args) => void[]

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1156

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] ]

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName

E

Returns

(...args) => void[]

Since

v0.1.26

Inherited from

Transform.listeners

Call Signature

listeners(eventName): (...args) => void[]

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1157

Parameters

eventName

string | symbol

Returns

(...args) => void[]

Inherited from

Transform.listeners

map()

map(fn, options?): Readable

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:522

This method allows mapping over the stream. The fn function will be called for every chunk in the stream. If the fn function returns a promise - that promise will be awaited before being passed to the result stream.

Parameters

fn

(data, options?) => any

a function to map over every chunk in the stream. Async or not.

options?

ReadableOperatorOptions

Returns

Readable

a stream mapped with the function fn.

Since

v17.4.0, v16.14.0

Inherited from

Transform.map

off()

Call Signature

off<E>(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1158

Alias for emitter.removeListener().

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName

E

listener

(...args) => void

Returns

this

Since

v10.0.0

Inherited from

Transform.off

Call Signature

off(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1159

Parameters

eventName

string | symbol

listener

(...args) => void

Returns

this

Inherited from

Transform.off

on()

Call Signature

on<E>(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1160

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 eventName and 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. The emitter.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

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName

E

The name of the event.

listener

(...args) => void

The callback function

Returns

this

Since

v0.1.101

Inherited from

Transform.on

Call Signature

on(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1161

Parameters

eventName

string | symbol

listener

(...args) => void

Returns

this

Inherited from

Transform.on

once()

Call Signature

once<E>(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1162

Adds a one-time listener 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. The emitter.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

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName

E

The name of the event.

listener

(...args) => void

The callback function

Returns

this

Since

v0.3.0

Inherited from

Transform.once

Call Signature

once(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1163

Parameters

eventName

string | symbol

listener

(...args) => void

Returns

this

Inherited from

Transform.once

pause()

pause(): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:318

The readable.pause() method will cause a stream in flowing mode to stop emitting 'data' events, switching out of flowing mode. Any data that becomes available will remain in the internal buffer.

const readable = getReadableStreamSomehow();
readable.on('data', (chunk) => {
  console.log(`Received ${chunk.length} bytes of data.`);
  readable.pause();
  console.log('There will be no additional data for 1 second.');
  setTimeout(() => {
    console.log('Now data will start flowing again.');
    readable.resume();
  }, 1000);
});

The readable.pause() method has no effect if there is a 'readable' event listener.

Returns

this

Since

v0.9.4

Inherited from

Transform.pause

pipe()

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

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:29

Type Parameters

T

T extends WritableStream

Parameters

destination

T

options?

PipeOptions

Returns

T

Since

v0.9.4

Inherited from

Transform.pipe

prependListener()

Call Signature

prependListener<E>(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1164

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 eventName and 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.

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName

E

The name of the event.

listener

(...args) => void

The callback function

Returns

this

Since

v6.0.0

Inherited from

Transform.prependListener

Call Signature

prependListener(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1168

Parameters

eventName

string | symbol

listener

(...args) => void

Returns

this

Inherited from

Transform.prependListener

prependOnceListener()

Call Signature

prependOnceListener<E>(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1169

Adds a one-time listener 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.

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName

E

The name of the event.

listener

(...args) => void

The callback function

Returns

this

Since

v6.0.0

Inherited from

Transform.prependOnceListener

Call Signature

prependOnceListener(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1173

Parameters

eventName

string | symbol

listener

(...args) => void

Returns

this

Inherited from

Transform.prependOnceListener

push()

push(chunk, encoding?): boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:474

Parameters

chunk

any

encoding?

BufferEncoding

Returns

boolean

Inherited from

Transform.push

rawListeners()

Call Signature

rawListeners<E>(eventName): (...args) => void[]

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1174

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');

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName

E

Returns

(...args) => void[]

Since

v9.4.0

Inherited from

Transform.rawListeners

Call Signature

rawListeners(eventName): (...args) => void[]

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1175

Parameters

eventName

string | symbol

Returns

(...args) => void[]

Inherited from

Transform.rawListeners

read()

read(size?): any

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:271

The readable.read() method reads data out of the internal buffer and returns it. If no data is available to be read, null is returned. By default, the data is returned as a Buffer object unless an encoding has been specified using the readable.setEncoding() method or the stream is operating in object mode.

The optional size argument specifies a specific number of bytes to read. If size bytes are not available to be read, null will be returned unless the stream has ended, in which case all of the data remaining in the internal buffer will be returned.

If the size argument is not specified, all of the data contained in the internal buffer will be returned.

The size argument must be less than or equal to 1 GiB.

The readable.read() method should only be called on Readable streams operating in paused mode. In flowing mode, readable.read() is called automatically until the internal buffer is fully drained.

const readable = getReadableStreamSomehow();

// 'readable' may be triggered multiple times as data is buffered in
readable.on('readable', () => {
  let chunk;
  console.log('Stream is readable (new data received in buffer)');
  // Use a loop to make sure we read all currently available data
  while (null !== (chunk = readable.read())) {
    console.log(`Read ${chunk.length} bytes of data...`);
  }
});

// 'end' will be triggered once when there is no more data available
readable.on('end', () => {
  console.log('Reached end of stream.');
});

Each call to readable.read() returns a chunk of data, or null. The chunks are not concatenated. A while loop is necessary to consume all data currently in the buffer. When reading a large file .read() may return null, having consumed all buffered content so far, but there is still more data to come not yet buffered. In this case a new 'readable' event will be emitted when there is more data in the buffer. Finally the 'end' event will be emitted when there is no more data to come.

Therefore to read a file's whole contents from a readable, it is necessary to collect chunks across multiple 'readable' events:

const chunks = [];

readable.on('readable', () => {
  let chunk;
  while (null !== (chunk = readable.read())) {
    chunks.push(chunk);
  }
});

readable.on('end', () => {
  const content = chunks.join('');
});

A Readable stream in object mode will always return a single item from a call to readable.read(size), regardless of the value of the size argument.

If the readable.read() method returns a chunk of data, a 'data' event will also be emitted.

Calling read after the 'end' event has been emitted will return null. No runtime error will be raised.

Parameters

size?

number

Optional argument to specify how much data to read.

Returns

any

Since

v0.9.4

Inherited from

Transform.read

reduce()

Call Signature

reduce<T>(fn): Promise<T>

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:649

This method calls fn on each chunk of the stream in order, passing it the result from the calculation on the previous element. It returns a promise for the final value of the reduction.

If no initial value is supplied the first chunk of the stream is used as the initial value. If the stream is empty, the promise is rejected with a TypeError with the ERR_INVALID_ARGS code property.

The reducer function iterates the stream element-by-element which means that there is no concurrency parameter or parallelism. To perform a reduce concurrently, you can extract the async function to readable.map method.

Type Parameters

T

T

Parameters

fn

(previous, data, options?) => T

a reducer function to call over every chunk in the stream. Async or not.

Returns

Promise<T>

a promise for the final value of the reduction.

Since

v17.5.0

Inherited from

Transform.reduce

Call Signature

reduce<T>(fn, initial, options?): Promise<T>

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:650

This method calls fn on each chunk of the stream in order, passing it the result from the calculation on the previous element. It returns a promise for the final value of the reduction.

Type Parameters

T

T

Parameters

fn

(previous, data, options?) => T

a reducer function to call over every chunk in the stream. Async or not.

initial

T

the initial value to use in the reduction.

options?

Abortable

Returns

Promise<T>

a promise for the final value of the reduction.

Since

v17.5.0

Inherited from

Transform.reduce

removeAllListeners()

Call Signature

removeAllListeners<E>(eventName?): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1177

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.

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName?

E

Returns

this

Since

v0.1.26

Inherited from

Transform.removeAllListeners

Call Signature

removeAllListeners(eventName?): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1178

Parameters

eventName?

string | symbol

Returns

this

Inherited from

Transform.removeAllListeners

removeListener()

Call Signature

removeListener<E>(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1179

Removes the specified listener from the listener array for the event named eventName.

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 any removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution will not remove them from emit() 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 indexes 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.

Type Parameters

E

E extends keyof DuplexEventMap

Parameters

eventName

E

listener

(...args) => void

Returns

this

Since

v0.1.26

Inherited from

Transform.removeListener

Call Signature

removeListener(eventName, listener): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1183

Parameters

eventName

string | symbol

listener

(...args) => void

Returns

this

Inherited from

Transform.removeListener

resume()

resume(): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:337

The readable.resume() method causes an explicitly paused Readable stream to resume emitting 'data' events, switching the stream into flowing mode.

The readable.resume() method can be used to fully consume the data from a stream without actually processing any of that data:

getReadableStreamSomehow()
  .resume()
  .on('end', () => {
    console.log('Reached the end, but did not read anything.');
  });

The readable.resume() method has no effect if there is a 'readable' event listener.

Returns

this

Since

v0.9.4

Inherited from

Transform.resume

setDefaultEncoding()

setDefaultEncoding(encoding): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:913

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

Parameters

encoding

BufferEncoding

The new default encoding

Returns

this

Since

v0.11.15

Inherited from

Transform.setDefaultEncoding

setEncoding()

setEncoding(encoding): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:296

The readable.setEncoding() method sets the character encoding for data read from the Readable stream.

By default, no encoding is assigned and stream data will be returned as Buffer objects. Setting an encoding causes the stream data to be returned as strings of the specified encoding rather than as Buffer objects. For instance, calling readable.setEncoding('utf8') will cause the output data to be interpreted as UTF-8 data, and passed as strings. Calling readable.setEncoding('hex') will cause the data to be encoded in hexadecimal string format.

The Readable stream will properly handle multi-byte characters delivered through the stream that would otherwise become improperly decoded if simply pulled from the stream as Buffer objects.

const readable = getReadableStreamSomehow();
readable.setEncoding('utf8');
readable.on('data', (chunk) => {
  assert.equal(typeof chunk, 'string');
  console.log('Got %d characters of string data:', chunk.length);
});

Parameters

encoding

BufferEncoding

The encoding to use.

Returns

this

Since

v0.9.4

Inherited from

Transform.setEncoding

setMaxListeners()

setMaxListeners(n): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/events.d.ts:472

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 to Infinity (or 0) to indicate an unlimited number of listeners.

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

Parameters

n

number

Returns

this

Since

v0.3.5

Inherited from

Transform.setMaxListeners

some()

some(fn, options?): Promise<boolean>

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:572

This method is similar to Array.prototype.some and calls fn on each chunk in the stream until the awaited return value is true (or any truthy value). Once an fn call on a chunk awaited return value is truthy, the stream is destroyed and the promise is fulfilled with true. If none of the fn calls on the chunks return a truthy value, the promise is fulfilled with false.

Parameters

fn

(data, options?) => boolean | Promise<boolean>

a function to call on each chunk of the stream. Async or not.

options?

Pick<ReadableOperatorOptions, "concurrency" | "signal">

Returns

Promise<boolean>

a promise evaluating to true if fn returned a truthy value for at least one of the chunks.

Since

v17.5.0

Inherited from

Transform.some

take()

take(limit, options?): Readable

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:634

This method returns a new stream with the first limit chunks.

Parameters

limit

number

the number of chunks to take from the readable.

options?

Abortable

Returns

Readable

a stream with limit chunks taken.

Since

v17.5.0

Inherited from

Transform.take

toArray()

toArray(options?): Promise<any[]>

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:562

This method allows easily obtaining the contents of a stream.

As this method reads the entire stream into memory, it negates the benefits of streams. It's intended for interoperability and convenience, not as the primary way to consume streams.

Parameters

options?

Abortable

Returns

Promise<any[]>

a promise containing an array with the contents of the stream.

Since

v17.5.0

Inherited from

Transform.toArray

uncork()

uncork(): void

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:987

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() using process.nextTick(). Doing so allows batching of all writable.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();
});

Returns

void

Since

v0.11.2

Inherited from

Transform.uncork

unpipe()

unpipe(destination?): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:381

The readable.unpipe() method detaches a Writable stream previously attached using the pipe method.

If the destination is not specified, then all pipes are detached.

If the destination is specified, but no pipe is set up for it, then the method does nothing.

import fs from 'node:fs';
const readable = getReadableStreamSomehow();
const writable = fs.createWriteStream('file.txt');
// All the data from readable goes into 'file.txt',
// but only for the first second.
readable.pipe(writable);
setTimeout(() => {
  console.log('Stop writing to file.txt.');
  readable.unpipe(writable);
  console.log('Manually close the file stream.');
  writable.end();
}, 1000);

Parameters

destination?

WritableStream

Optional specific stream to unpipe

Returns

this

Since

v0.9.4

Inherited from

Transform.unpipe

unshift()

unshift(chunk, encoding?): void

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:447

Passing chunk as null signals the end of the stream (EOF) and behaves the same as readable.push(null), after which no more data can be written. The EOF signal is put at the end of the buffer and any buffered data will still be flushed.

The readable.unshift() method pushes a chunk of data back into the internal buffer. This is useful in certain situations where a stream is being consumed by code that needs to "un-consume" some amount of data that it has optimistically pulled out of the source, so that the data can be passed on to some other party.

The stream.unshift(chunk) method cannot be called after the 'end' event has been emitted or a runtime error will be thrown.

Developers using stream.unshift() often should consider switching to use of a Transform stream instead. See the API for stream implementers section for more information.

// Pull off a header delimited by \n\n.
// Use unshift() if we get too much.
// Call the callback with (error, header, stream).
import { StringDecoder } from 'node:string_decoder';
function parseHeader(stream, callback) {
  stream.on('error', callback);
  stream.on('readable', onReadable);
  const decoder = new StringDecoder('utf8');
  let header = '';
  function onReadable() {
    let chunk;
    while (null !== (chunk = stream.read())) {
      const str = decoder.write(chunk);
      if (str.includes('\n\n')) {
        // Found the header boundary.
        const split = str.split(/\n\n/);
        header += split.shift();
        const remaining = split.join('\n\n');
        const buf = Buffer.from(remaining, 'utf8');
        stream.removeListener('error', callback);
        // Remove the 'readable' listener before unshifting.
        stream.removeListener('readable', onReadable);
        if (buf.length)
          stream.unshift(buf);
        // Now the body of the message can be read from the stream.
        callback(null, header, stream);
        return;
      }
      // Still reading the header.
      header += str;
    }
  }
}

Unlike push, stream.unshift(chunk) will not end the reading process by resetting the internal reading state of the stream. This can cause unexpected results if readable.unshift() is called during a read (i.e. from within a _read implementation on a custom stream). Following the call to readable.unshift() with an immediate push will reset the reading state appropriately, however it is best to simply avoid calling readable.unshift() while in the process of performing a read.

Parameters

chunk

any

Chunk of data to unshift onto the read queue. For streams not operating in object mode, chunk must be a {string}, {Buffer}, {TypedArray}, {DataView} or null. For object mode streams, chunk may be any JavaScript value.

encoding?

BufferEncoding

Encoding of string chunks. Must be a valid Buffer encoding, such as 'utf8' or 'ascii'.

Returns

void

Since

v0.9.11

Inherited from

Transform.unshift

wrap()

wrap(stream): this

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:473

Prior to Node.js 0.10, streams did not implement the entire node:stream module API as it is currently defined. (See Compatibility for more information.)

When using an older Node.js library that emits 'data' events and has a pause method that is advisory only, the readable.wrap() method can be used to create a Readable stream that uses the old stream as its data source.

It will rarely be necessary to use readable.wrap() but the method has been provided as a convenience for interacting with older Node.js applications and libraries.

import { OldReader } from './old-api-module.js';
import { Readable } from 'node:stream';
const oreader = new OldReader();
const myReader = new Readable().wrap(oreader);

myReader.on('readable', () => {
  myReader.read(); // etc.
});

Parameters

stream

ReadableStream

An "old style" readable stream

Returns

this

Since

v0.9.4

Inherited from

Transform.wrap

write()

Call Signature

write(chunk, callback?): boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:906

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 the highWaterMark 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

chunk

any

Optional data to write. For streams not operating in object mode, chunk must be a {string}, {Buffer}, {TypedArray} or {DataView}. For object mode streams, chunk may be any JavaScript value other than null.

callback?

(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

Inherited from

Transform.write

Call Signature

write(chunk, encoding, callback?): boolean

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:907

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

chunk

any

encoding

BufferEncoding

The encoding, if chunk is a string.

callback?

(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

Inherited from

Transform.write

from()

static from(src): Duplex

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1102

A utility method for creating duplex streams.

Stream converts writable stream into writable Duplex and readable stream to Duplex.
Blob converts into readable Duplex.
string converts into readable Duplex.
ArrayBuffer converts into readable Duplex.
AsyncIterable converts into a readable Duplex. Cannot yield null.
AsyncGeneratorFunction converts into a readable/writable transform Duplex. Must take a source AsyncIterable as first parameter. Cannot yield null.
AsyncFunction converts into a writable Duplex. Must return either null or undefined
Object ({ writable, readable }) converts readable and writable into Stream and then combines them into Duplex where the Duplex will write to the writable and read from the readable.
Promise converts into readable Duplex. Value null is ignored.

Parameters

src

Returns

Duplex

Since

v16.8.0

Inherited from

Transform.from

fromWeb()

static fromWeb(duplexStream, options?): Duplex

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1126

A utility method for creating a Duplex from a web ReadableStream and WritableStream.

Parameters

duplexStream

ReadableWritablePair

options?

Returns

Duplex

Since

v17.0.0

Inherited from

Transform.fromWeb

toWeb()

static toWeb(streamDuplex, options?): ReadableWritablePair

Defined in: node_modules/.pnpm/@types+node@25.5.0/node_modules/@types/node/stream.d.ts:1121

A utility method for creating a web ReadableStream and WritableStream from a Duplex.

Parameters

streamDuplex

ReadWriteStream

options?

DuplexToWebOptions

Returns

ReadableWritablePair

Since

v17.0.0

Inherited from

Transform.toWeb

Class: GunzipConditional

Extends​

Constructors​

Constructor​

Parameters​

options?​

Returns​

Inherited from​

Properties​

allowHalfOpen​

Since​

Inherited from​

closed​

Since​

Inherited from​

destroyed​

Since​

Inherited from​

errored​

Since​

Inherited from​

first​

readable​

Since​

Inherited from​

readableAborted​

Since​

Inherited from​

readableDidRead​

Since​

Inherited from​

readableEncoding​

Since​

Inherited from​

readableEnded​

Since​

Inherited from​

readableFlowing​

Since​

Inherited from​

readableHighWaterMark​

Since​

Inherited from​

readableLength​

Since​

Inherited from​

readableObjectMode​

Since​

Inherited from​

writable​

Since​

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writableAborted​

Since​

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writableCorked​

Since​

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writableEnded​

Since​

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writableFinished​

Since​

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writableHighWaterMark​

Since​

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writableLength​

Since​

Inherited from​

writableNeedDrain​

Since​

Inherited from​

writableObjectMode​

Since​

Inherited from​

zlib​

Methods​

_construct()?​

Parameters​

Extends

Constructors

Constructor

Parameters

options?

Returns

Inherited from

Properties

allowHalfOpen

Since

Inherited from

closed

Since

Inherited from

destroyed

Since

Inherited from

errored

Since

Inherited from

first

readable

Since

Inherited from

readableAborted

Since

Inherited from

readableDidRead

Since

Inherited from

readableEncoding

Since

Inherited from

readableEnded

Since

Inherited from

readableFlowing

Since

Inherited from

readableHighWaterMark

Since

Inherited from

readableLength

Since

Inherited from

readableObjectMode

Since

Inherited from

writable

Since

Inherited from

writableAborted

Since

Inherited from

writableCorked

Since

Inherited from

writableEnded

Since

Inherited from

writableFinished

Since

Inherited from

writableHighWaterMark

Since

Inherited from

writableLength

Since

Inherited from

writableNeedDrain

Since

Inherited from

writableObjectMode

Since

Inherited from

zlib

Methods

_construct()?

Parameters

callback