ReadStream

Defined in: src/node/streams.ts:54

A ReadStream implementation that wraps an underlying global ReadableStream.

Extends

Readable

Implements

ReadStream

Constructors

Constructor

new ReadStream(opts?, handleOrPromise): ReadStream

Defined in: src/node/streams.ts:61

Parameters

opts?

CreateReadStreamOptions = {}

handleOrPromise

FileHandle | Promise<FileHandle>

Returns

ReadStream

Overrides

Readable.constructor

Properties

closed

readonly closed: boolean

Defined in: node_modules/@types/node/stream.d.ts:168

Is true after 'close' has been emitted.

Since

v18.0.0

Implementation of

fs.ReadStream.closed

Inherited from

Readable.closed

destroyed

destroyed: boolean

Defined in: node_modules/@types/node/stream.d.ts:163

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

Since

v8.0.0

Implementation of

fs.ReadStream.destroyed

Inherited from

Readable.destroyed

errored

readonly errored: Error | null

Defined in: node_modules/@types/node/stream.d.ts:173

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

Since

v18.0.0

Implementation of

fs.ReadStream.errored

Inherited from

Readable.errored

pending

pending: boolean = true

Defined in: src/node/streams.ts:55

This property is true if the underlying file has not been opened yet, i.e. before the 'ready' event is emitted.

Since

v11.2.0, v10.16.0

Implementation of

fs.ReadStream.pending

readable

readable: boolean

Defined in: node_modules/@types/node/stream.d.ts:120

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

Implementation of

fs.ReadStream.readable

Inherited from

Readable.readable

readableAborted

readonly readableAborted: boolean

Defined in: node_modules/@types/node/stream.d.ts:114

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

Since

v16.8.0

Implementation of

fs.ReadStream.readableAborted

Inherited from

Readable.readableAborted

readableDidRead

readonly readableDidRead: boolean

Defined in: node_modules/@types/node/stream.d.ts:125

Returns whether 'data' has been emitted.

Since

v16.7.0, v14.18.0

Implementation of

fs.ReadStream.readableDidRead

Inherited from

Readable.readableDidRead

readableEncoding

readonly readableEncoding: BufferEncoding | null

Defined in: node_modules/@types/node/stream.d.ts:130

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

Since

v12.7.0

Implementation of

fs.ReadStream.readableEncoding

Inherited from

Readable.readableEncoding

readableEnded

readonly readableEnded: boolean

Defined in: node_modules/@types/node/stream.d.ts:135

Becomes true when 'end' event is emitted.

Since

v12.9.0

Implementation of

fs.ReadStream.readableEnded

Inherited from

Readable.readableEnded

readableFlowing

readableFlowing: boolean | null

Defined in: node_modules/@types/node/stream.d.ts:141

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

Since

v9.4.0

Implementation of

fs.ReadStream.readableFlowing

Inherited from

Readable.readableFlowing

readableHighWaterMark

readonly readableHighWaterMark: number

Defined in: node_modules/@types/node/stream.d.ts:146

Returns the value of highWaterMark passed when creating this Readable.

Since

v9.3.0

Implementation of

fs.ReadStream.readableHighWaterMark

Inherited from

Readable.readableHighWaterMark

readableLength

readonly readableLength: number

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

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

Implementation of

fs.ReadStream.readableLength

Inherited from

Readable.readableLength

readableObjectMode

readonly readableObjectMode: boolean

Defined in: node_modules/@types/node/stream.d.ts:158

Getter for the property objectMode of a given Readable stream.

Since

v12.3.0

Implementation of

fs.ReadStream.readableObjectMode

Inherited from

Readable.readableObjectMode

Accessors

bytesRead

Get Signature

get bytesRead(): number

Defined in: src/node/streams.ts:108

The number of bytes that have been read so far.

Since

v6.4.0

Returns

number

Implementation of

fs.ReadStream.bytesRead

path

Get Signature

get path(): string

Defined in: src/node/streams.ts:104

The path to the file the stream is reading from as specified in the first argument to fs.createReadStream(). If path is passed as a string, thenreadStream.path will be a string. If path is passed as a Buffer, thenreadStream.path will be a Buffer. If fd is specified, thenreadStream.path will be undefined.

Since

v0.1.93

Returns

string

Implementation of

fs.ReadStream.path

Methods

_construct()?

optional _construct(callback): void

Defined in: node_modules/@types/node/stream.d.ts:174

Parameters

callback

(error?) => void

Returns

void

Implementation of

fs.ReadStream._construct

Inherited from

Readable._construct

_destroy()

_destroy(error, callback): void

Defined in: node_modules/@types/node/stream.d.ts:637

Parameters

error

Error | null

callback

(error?) => void

Returns

void

Implementation of

fs.ReadStream._destroy

Inherited from

Readable._destroy

_read()

_read(): Promise<void>

Defined in: src/node/streams.ts:78

Returns

Promise<void>

Implementation of

fs.ReadStream._read

Overrides

Readable._read

[asyncDispose]()

[asyncDispose](): Promise<void>

Defined in: node_modules/@types/node/stream.d.ts:691

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

Returns

Promise<void>

Since

v20.4.0

Implementation of

fs.ReadStream.[asyncDispose]

Inherited from

Readable.[asyncDispose]

[asyncIterator]()

[asyncIterator](): AsyncIterator<any>

Defined in: node_modules/@types/node/stream.d.ts:654

Returns

AsyncIterator<any>

AsyncIterator to fully consume the stream.

Since

v10.0.0

Implementation of

fs.ReadStream.[asyncIterator]

Inherited from

Readable.[asyncIterator]

[captureRejectionSymbol]()?

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

Defined in: node_modules/@types/node/events.d.ts:87

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

Implementation of

fs.ReadStream.[captureRejectionSymbol]

Inherited from

Readable.[captureRejectionSymbol]

[toAsyncStreamable]()

[toAsyncStreamable](): ByteReadableStream

Defined in: node_modules/@types/node/stream.d.ts:685

When the --experimental-stream-iter flag is enabled, Readable streams implement the Stream.toAsyncStreamable protocol, enabling efficient consumption by the stream/iter API.

This provides a batched async iterator that drains the stream’s internal buffer into Uint8Array[] batches, amortizing the per-chunk Promise overhead of the standard Symbol.asyncIterator path. For byte-mode streams, chunks are yielded directly as Buffer instances (which are Uint8Array subclasses). For object-mode or encoded streams, each chunk is normalized to Uint8Array before batching.

The returned iterator is tagged as a validated source, so from() passes it through without additional normalization.

import { Readable } from 'node:stream';
import { text, from } from 'node:stream/iter';

const readable = new Readable({
  read() { this.push('hello'); this.push(null); },
});

// Readable is automatically consumed via toAsyncStreamable
console.log(await text(from(readable))); // 'hello'

Without the --experimental-stream-iter flag, calling this method throws ERR_STREAM_ITER_MISSING_FLAG.

Returns

ByteReadableStream

Implementation of

fs.ReadStream.[toAsyncStreamable]

Inherited from

Readable.[toAsyncStreamable]

addListener()

Call Signature

addListener<E>(eventName, listener): this

Defined in: node_modules/@types/node/stream.d.ts:693

Alias for emitter.on(eventName, listener).

Type Parameters

E

E extends keyof ReadableEventMap

Parameters

eventName

E

listener

(…args) => void

Returns

this

Since

v0.1.26

Implementation of

fs.ReadStream.addListener

Inherited from

Readable.addListener

Call Signature

addListener(eventName, listener): this

Defined in: node_modules/@types/node/stream.d.ts:697

Parameters

eventName

string | symbol

listener

(…args) => void

Returns

this

Implementation of

fs.ReadStream.addListener

Inherited from

Readable.addListener

close()

close(callback?): void

Defined in: src/node/streams.ts:99

Like Node, the callback is invoked once the stream is closed. Closing before the stream has finished reports ERR_STREAM_PREMATURE_CLOSE.

Parameters

callback?

Callback<[void]> = ...

Returns

void

Implementation of

fs.ReadStream.close

compose()

compose(stream, options?): Duplex

Defined in: node_modules/@types/node/stream.d.ts:486

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

Implementation of

fs.ReadStream.compose

Inherited from

Readable.compose

destroy()

destroy(error?): this

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

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

Implementation of

fs.ReadStream.destroy

Inherited from

Readable.destroy

drop()

drop(limit, options?): Readable

Defined in: node_modules/@types/node/stream.d.ts:609

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

Implementation of

fs.ReadStream.drop

Inherited from

Readable.drop

emit()

Call Signature

emit<E>(eventName, …args): boolean

Defined in: node_modules/@types/node/stream.d.ts:698

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 ReadableEventMap

Parameters

eventName

E

args

…ReadableEventMap[E]

Returns

boolean

Since

v0.1.26

Implementation of

fs.ReadStream.emit

Inherited from

Readable.emit

Call Signature

emit(eventName, …args): boolean

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

Parameters

eventName

string | symbol

args

…any[]

Returns

boolean

Implementation of

fs.ReadStream.emit

Inherited from

Readable.emit

eventNames()

eventNames(): (string | symbol)[]

Defined in: node_modules/@types/node/events.d.ts:154

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

Implementation of

fs.ReadStream.eventNames

Inherited from

Readable.eventNames

every()

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

Defined in: node_modules/@types/node/stream.d.ts:585

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, "signal" | "concurrency">

Returns

Promise<boolean>

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

Since

v17.5.0

Implementation of

fs.ReadStream.every

Inherited from

Readable.every

filter()

filter(fn, options?): Readable

Defined in: node_modules/@types/node/stream.d.ts:513

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

Implementation of

fs.ReadStream.filter

Inherited from

Readable.filter

find()

Call Signature

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

Defined in: node_modules/@types/node/stream.d.ts:568

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, "signal" | "concurrency">

Returns

Promise<T | undefined>

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

Implementation of

fs.ReadStream.find

Inherited from

Readable.find

Call Signature

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

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

Parameters

fn

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

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

options?

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

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

Implementation of

fs.ReadStream.find

Inherited from

Readable.find

flatMap()

flatMap(fn, options?): Readable

Defined in: node_modules/@types/node/stream.d.ts:599

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, "signal" | "concurrency">

Returns

Readable

a stream flat-mapped with the function fn.

Since

v17.5.0

Implementation of

fs.ReadStream.flatMap

Inherited from

Readable.flatMap

forEach()

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

Defined in: node_modules/@types/node/stream.d.ts:532

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, "signal" | "concurrency">

Returns

Promise<void>

a promise for when the stream has finished.

Since

v17.5.0

Implementation of

fs.ReadStream.forEach

Inherited from

Readable.forEach

getMaxListeners()

getMaxListeners(): number

Defined in: node_modules/@types/node/events.d.ts:161

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

Implementation of

fs.ReadStream.getMaxListeners

Inherited from

Readable.getMaxListeners

isPaused()

isPaused(): boolean

Defined in: node_modules/@types/node/stream.d.ts:336

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

Implementation of

fs.ReadStream.isPaused

Inherited from

Readable.isPaused

iterator()

iterator(options?): AsyncIterator<any>

Defined in: node_modules/@types/node/stream.d.ts:496

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

Implementation of

fs.ReadStream.iterator

Inherited from

Readable.iterator

listenerCount()

Call Signature

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

Defined in: node_modules/@types/node/stream.d.ts:700

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 ReadableEventMap

Parameters

eventName

E

The name of the event being listened for

listener?

(…args) => void

The event handler function

Returns

number

Since

v3.2.0

Implementation of

fs.ReadStream.listenerCount

Inherited from

Readable.listenerCount

Call Signature

listenerCount(eventName, listener?): number

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

Parameters

eventName

string | symbol

listener?

(…args) => void

Returns

number

Implementation of

fs.ReadStream.listenerCount

Inherited from

Readable.listenerCount

listeners()

Call Signature

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

Defined in: node_modules/@types/node/stream.d.ts:705

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 ReadableEventMap

Parameters

eventName

E

Returns

(…args) => void[]

Since

v0.1.26

Implementation of

fs.ReadStream.listeners

Inherited from

Readable.listeners

Call Signature

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

Defined in: node_modules/@types/node/stream.d.ts:706

Parameters

eventName

string | symbol

Returns

(…args) => void[]

Implementation of

fs.ReadStream.listeners

Inherited from

Readable.listeners

map()

map(fn, options?): Readable

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

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

Implementation of

fs.ReadStream.map

Inherited from

Readable.map

off()

Call Signature

off<E>(eventName, listener): this

Defined in: node_modules/@types/node/stream.d.ts:707

Alias for emitter.removeListener().

Type Parameters

E

E extends keyof ReadableEventMap

Parameters

eventName

E

listener

(…args) => void

Returns

this

Since

v10.0.0

Implementation of

fs.ReadStream.off

Inherited from

Readable.off

Call Signature

off(eventName, listener): this

Defined in: node_modules/@types/node/stream.d.ts:708

Parameters

eventName

string | symbol

listener

(…args) => void

Returns

this

Implementation of

fs.ReadStream.off

Inherited from

Readable.off

on()

Call Signature

on<E>(eventName, listener): this

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

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 ReadableEventMap

Parameters

eventName

E

The name of the event.

listener

(…args) => void

The callback function

Returns

this

Since

v0.1.101

Implementation of

fs.ReadStream.on

Inherited from

Readable.on

Call Signature

on(eventName, listener): this

Defined in: node_modules/@types/node/stream.d.ts:710

Parameters

eventName

string | symbol

listener

(…args) => void

Returns

this

Implementation of

fs.ReadStream.on

Inherited from

Readable.on

once()

Call Signature

once<E>(eventName, listener): this

Defined in: node_modules/@types/node/stream.d.ts:711

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 ReadableEventMap

Parameters

eventName

E

The name of the event.

listener

(…args) => void

The callback function

Returns

this

Since

v0.3.0

Implementation of

fs.ReadStream.once

Inherited from

Readable.once

Call Signature

once(eventName, listener): this

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

Parameters

eventName

string | symbol

listener

(…args) => void

Returns

this

Implementation of

fs.ReadStream.once

Inherited from

Readable.once

pause()

pause(): this

Defined in: node_modules/@types/node/stream.d.ts:300

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

Implementation of

fs.ReadStream.pause

Inherited from

Readable.pause

pipe()

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

Defined in: node_modules/@types/node/stream.d.ts:11

Type Parameters

T

T extends WritableStream

Parameters

destination

T

options?

PipeOptions

Returns

T

Since

v0.9.4

Implementation of

fs.ReadStream.pipe

Inherited from

Readable.pipe

prependListener()

Call Signature

prependListener<E>(eventName, listener): this

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

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 ReadableEventMap

Parameters

eventName

E

The name of the event.

listener

(…args) => void

The callback function

Returns

this

Since

v6.0.0

Implementation of

fs.ReadStream.prependListener

Inherited from

Readable.prependListener

Call Signature

prependListener(eventName, listener): this

Defined in: node_modules/@types/node/stream.d.ts:720

Parameters

eventName

string | symbol

listener

(…args) => void

Returns

this

Implementation of

fs.ReadStream.prependListener

Inherited from

Readable.prependListener

prependOnceListener()

Call Signature

prependOnceListener<E>(eventName, listener): this

Defined in: node_modules/@types/node/stream.d.ts:721

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 ReadableEventMap

Parameters

eventName

E

The name of the event.

listener

(…args) => void

The callback function

Returns

this

Since

v6.0.0

Implementation of

fs.ReadStream.prependOnceListener

Inherited from

Readable.prependOnceListener

Call Signature

prependOnceListener(eventName, listener): this

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

Parameters

eventName

string | symbol

listener

(…args) => void

Returns

this

Implementation of

fs.ReadStream.prependOnceListener

Inherited from

Readable.prependOnceListener

push()

push(chunk, encoding?): boolean

Defined in: node_modules/@types/node/stream.d.ts:456

Parameters

chunk

any

encoding?

BufferEncoding

Returns

boolean

Implementation of

fs.ReadStream.push

Inherited from

Readable.push

rawListeners()

Call Signature

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

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

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 ReadableEventMap

Parameters

eventName

E

Returns

(…args) => void[]

Since

v9.4.0

Implementation of

fs.ReadStream.rawListeners

Inherited from

Readable.rawListeners

Call Signature

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

Defined in: node_modules/@types/node/stream.d.ts:727

Parameters

eventName

string | symbol

Returns

(…args) => void[]

Implementation of

fs.ReadStream.rawListeners

Inherited from

Readable.rawListeners

read()

read(size?): any

Defined in: node_modules/@types/node/stream.d.ts:253

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

Implementation of

fs.ReadStream.read

Inherited from

Readable.read

reduce()

Call Signature

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

Defined in: node_modules/@types/node/stream.d.ts:631

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

Implementation of

fs.ReadStream.reduce

Inherited from

Readable.reduce

Call Signature

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

Defined in: node_modules/@types/node/stream.d.ts:632

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

Implementation of

fs.ReadStream.reduce

Inherited from

Readable.reduce

removeAllListeners()

Call Signature

removeAllListeners<E>(eventName?): this

Defined in: node_modules/@types/node/stream.d.ts:729

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 ReadableEventMap

Parameters

eventName?

E

Returns

this

Since

v0.1.26

Implementation of

fs.ReadStream.removeAllListeners

Inherited from

Readable.removeAllListeners

Call Signature

removeAllListeners(eventName?): this

Defined in: node_modules/@types/node/stream.d.ts:730

Parameters

eventName?

string | symbol

Returns

this

Implementation of

fs.ReadStream.removeAllListeners

Inherited from

Readable.removeAllListeners

removeListener()

Call Signature

removeListener<E>(eventName, listener): this

Defined in: node_modules/@types/node/stream.d.ts:731

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 ReadableEventMap

Parameters

eventName

E

listener

(…args) => void

Returns

this

Since

v0.1.26

Implementation of

fs.ReadStream.removeListener

Inherited from

Readable.removeListener

Call Signature

removeListener(eventName, listener): this

Defined in: node_modules/@types/node/stream.d.ts:735

Parameters

eventName

string | symbol

listener

(…args) => void

Returns

this

Implementation of

fs.ReadStream.removeListener

Inherited from

Readable.removeListener

resume()

resume(): this

Defined in: node_modules/@types/node/stream.d.ts:319

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

Implementation of

fs.ReadStream.resume

Inherited from

Readable.resume

setEncoding()

setEncoding(encoding): this

Defined in: node_modules/@types/node/stream.d.ts:278

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

Implementation of

fs.ReadStream.setEncoding

Inherited from

Readable.setEncoding

setMaxListeners()

setMaxListeners(n): this

Defined in: node_modules/@types/node/events.d.ts:436

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

Implementation of

fs.ReadStream.setMaxListeners

Inherited from

Readable.setMaxListeners

some()

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

Defined in: node_modules/@types/node/stream.d.ts:554

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, "signal" | "concurrency">

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

Implementation of

fs.ReadStream.some

Inherited from

Readable.some

take()

take(limit, options?): Readable

Defined in: node_modules/@types/node/stream.d.ts:616

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

Implementation of

fs.ReadStream.take

Inherited from

Readable.take

toArray()

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

Defined in: node_modules/@types/node/stream.d.ts:544

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

Implementation of

fs.ReadStream.toArray

Inherited from

Readable.toArray

unpipe()

unpipe(destination?): this

Defined in: node_modules/@types/node/stream.d.ts:363

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

Implementation of

fs.ReadStream.unpipe

Inherited from

Readable.unpipe

unshift()

unshift(chunk, encoding?): void

Defined in: node_modules/@types/node/stream.d.ts:429

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

Implementation of

fs.ReadStream.unshift

Inherited from

Readable.unshift

wrap()

wrap(oldStream): this

Defined in: src/node/streams.ts:112

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

oldStream

ReadableStream

Returns

this

Since

v0.9.4

Implementation of

fs.ReadStream.wrap

Overrides

Readable.wrap

from()

static from(iterable, options?): Readable

Defined in: node_modules/@types/node/stream.d.ts:88

A utility method for creating Readable Streams out of iterators.

Parameters

iterable

Iterable<any, any, any> | AsyncIterable<any, any, any>

Object implementing the Symbol.asyncIterator or Symbol.iterator iterable protocol. Emits an ‘error’ event if a null value is passed.

options?

ReadableOptions<Readable>

Options provided to new stream.Readable([options]). By default, Readable.from() will set options.objectMode to true, unless this is explicitly opted out by setting options.objectMode to false.

Returns

Readable

Since

v12.3.0, v10.17.0

Inherited from

Readable.from

fromWeb()

static fromWeb(readableStream, options?): Readable

Defined in: node_modules/@types/node/stream.d.ts:93

A utility method for creating a Readable from a web ReadableStream.

Parameters

readableStream

ReadableStream

options?

Pick<ReadableOptions<Readable>, "encoding" | "highWaterMark" | "objectMode" | "signal">

Returns

Readable

Since

v17.0.0

Inherited from

Readable.fromWeb

isDisturbed()

static isDisturbed(stream): boolean

Defined in: node_modules/@types/node/stream.d.ts:109

Returns whether the stream has been read from or cancelled.

Parameters

stream

ReadableStream | ReadableStream<any>

Returns

boolean

Since

v16.8.0

Inherited from

Readable.isDisturbed

toWeb()

static toWeb(streamReadable, options?): ReadableStream

Defined in: node_modules/@types/node/stream.d.ts:101

A utility method for creating a web ReadableStream from a Readable.

Parameters

streamReadable

ReadableStream

options?

ReadableToWebOptions

Returns

ReadableStream

Since

v17.0.0

Inherited from

Readable.toWeb

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