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Stability: 2 - Stable

An implementation of the WHATWG Streams Standard.

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The WHATWG Streams Standard (or "web streams") defines an API for handling streaming data. It is similar to the Node.js Streams API but emerged later and has become the "standard" API for streaming data across many JavaScript environments.

There are three primary types of objects:

• ReadableStream - Represents a source of streaming data.
• WritableStream - Represents a destination for streaming data.
• TransformStream - Represents an algorithm for transforming streaming data.

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This example creates a simple ReadableStream that pushes the current performance.now() timestamp once every second forever. An async iterable is used to read the data from the stream.

import {
  ReadableStream,
} from 'node:stream/web';

import {
  setInterval as every,
} from 'node:timers/promises';

import {
  performance,
} from 'node:perf_hooks';

const SECOND = 1000;

const stream = new ReadableStream({
  async start(controller) {
    for await (const _ of every(SECOND))
      controller.enqueue(performance.now());
  },
});

for await (const value of stream)
  console.log(value);

const {
  ReadableStream,
} = require('node:stream/web');

const {
  setInterval: every,
} = require('node:timers/promises');

const {
  performance,
} = require('node:perf_hooks');

const SECOND = 1000;

const stream = new ReadableStream({
  async start(controller) {
    for await (const _ of every(SECOND))
      controller.enqueue(performance.now());
  },
});

(async () => {
  for await (const value of stream)
    console.log(value);
})();

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Node.js streams can be converted to web streams and vice versa via the toWeb and fromWeb methods present on stream.Readable, stream.Writable and stream.Duplex objects.

For more details refer to the relevant documentation:

• stream.Readable.toWeb
• stream.Readable.fromWeb
• stream.Writable.toWeb
• stream.Writable.fromWeb
• stream.Duplex.toWeb
• stream.Duplex.fromWeb

[object Object] [object Object] [object Object]

• underlyingSource <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • start <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked immediately when the ReadableStream is created.
    • controller <a href="webstreams.html#class-readablestreamdefaultcontroller" class="type"><ReadableStreamDefaultController></a> | <a href="webstreams.html#class-readablebytestreamcontroller" class="type"><ReadableByteStreamController></a>
    • Returns: undefined or a promise fulfilled with undefined.
  • pull <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called repeatedly when the ReadableStream internal queue is not full. The operation may be sync or async. If async, the function will not be called again until the previously returned promise is fulfilled.
    • controller <a href="webstreams.html#class-readablestreamdefaultcontroller" class="type"><ReadableStreamDefaultController></a> | <a href="webstreams.html#class-readablebytestreamcontroller" class="type"><ReadableByteStreamController></a>
    • Returns: A promise fulfilled with undefined.
  • cancel <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called when the ReadableStream is canceled.
    • reason <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
    • Returns: A promise fulfilled with undefined.
  • type <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#string_type" class="type"><string></a> Must be 'bytes' or undefined.
  • autoAllocateChunkSize <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a> Used only when type is equal to 'bytes'. When set to a non-zero value a view buffer is automatically allocated to ReadableByteStreamController.byobRequest. When not set one must use stream's internal queues to transfer data via the default reader ReadableStreamDefaultReader.
• strategy <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • highWaterMark <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a> The maximum internal queue size before backpressure is applied.
  • size <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each chunk of data.
    • chunk <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
    • Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a> Set to true if there is an active reader for this <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.

The readableStream.locked property is false by default, and is switched to true while there is an active reader consuming the stream's data.

[object Object]

• reason <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
• Returns: A promise fulfilled with undefined once cancelation has been completed.

[object Object]

• options <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • mode <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#string_type" class="type"><string></a> 'byob' or undefined
• Returns: <a href="webstreams.html#class-readablestreamdefaultreader" class="type"><ReadableStreamDefaultReader></a> | <a href="webstreams.html#class-readablestreambyobreader" class="type"><ReadableStreamBYOBReader></a>

import { ReadableStream } from 'node:stream/web';

const stream = new ReadableStream();

const reader = stream.getReader();

console.log(await reader.read());

const { ReadableStream } = require('node:stream/web');

const stream = new ReadableStream();

const reader = stream.getReader();

reader.read().then(console.log);

Causes the readableStream.locked to be true.

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• transform <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • readable <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> The ReadableStream to which transform.writable will push the potentially modified data it receives from this ReadableStream.
  • writable <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> The WritableStream to which this ReadableStream's data will be written.
• options <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • preventAbort <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a> When true, errors in this ReadableStream will not cause transform.writable to be aborted.
  • preventCancel <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a> When true, errors in the destination transform.writable do not cause this ReadableStream to be canceled.
  • preventClose <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a> When true, closing this ReadableStream does not cause transform.writable to be closed.
  • signal <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows the transfer of data to be canceled using an <a href="globals.html#class-abortcontroller" class="type"><AbortController></a>.
• Returns: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> From transform.readable.

Connects this <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to the pair of <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> provided in the transform argument such that the data from this <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> is written in to transform.writable, possibly transformed, then pushed to transform.readable. Once the pipeline is configured, transform.readable is returned.

Causes the readableStream.locked to be true while the pipe operation is active.

import {
  ReadableStream,
  TransformStream,
} from 'node:stream/web';

const stream = new ReadableStream({
  start(controller) {
    controller.enqueue('a');
  },
});

const transform = new TransformStream({
  transform(chunk, controller) {
    controller.enqueue(chunk.toUpperCase());
  },
});

const transformedStream = stream.pipeThrough(transform);

for await (const chunk of transformedStream)
  console.log(chunk);
  // Prints: A

const {
  ReadableStream,
  TransformStream,
} = require('node:stream/web');

const stream = new ReadableStream({
  start(controller) {
    controller.enqueue('a');
  },
});

const transform = new TransformStream({
  transform(chunk, controller) {
    controller.enqueue(chunk.toUpperCase());
  },
});

const transformedStream = stream.pipeThrough(transform);

(async () => {
  for await (const chunk of transformedStream)
    console.log(chunk);
    // Prints: A
})();

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• destination <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> A <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> to which this ReadableStream's data will be written.
• options <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • preventAbort <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a> When true, errors in this ReadableStream will not cause destination to be aborted.
  • preventCancel <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a> When true, errors in the destination will not cause this ReadableStream to be canceled.
  • preventClose <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a> When true, closing this ReadableStream does not cause destination to be closed.
  • signal <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> Allows the transfer of data to be canceled using an <a href="globals.html#class-abortcontroller" class="type"><AbortController></a>.
• Returns: A promise fulfilled with undefined

Causes the readableStream.locked to be true while the pipe operation is active.

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• Returns: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream[]></a>

Returns a pair of new <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> instances to which this ReadableStream's data will be forwarded. Each will receive the same data.

Causes the readableStream.locked to be true.

[object Object]

• options <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • preventCancel <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a> When true, prevents the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> from being closed when the async iterator abruptly terminates. Default: false.

Creates and returns an async iterator usable for consuming this ReadableStream's data.

Causes the readableStream.locked to be true while the async iterator is active.

import { Buffer } from 'node:buffer';

const stream = new ReadableStream(getSomeSource());

for await (const chunk of stream.values({ preventCancel: true }))
  console.log(Buffer.from(chunk).toString());

[object Object]

The <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> object supports the async iterator protocol using for await syntax.

import { Buffer } from 'node:buffer';

const stream = new ReadableStream(getSomeSource());

for await (const chunk of stream)
  console.log(Buffer.from(chunk).toString());

The async iterator will consume the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> until it terminates.

By default, if the async iterator exits early (via either a break, return, or a throw), the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> will be closed. To prevent automatic closing of the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>, use the readableStream.values() method to acquire the async iterator and set the preventCancel option to true.

The <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> must not be locked (that is, it must not have an existing active reader). During the async iteration, the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> will be locked.

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A <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> instance can be transferred using a <a href="worker_threads.html#class-messageport" class="type"><MessagePort></a>.

const stream = new ReadableStream(getReadableSourceSomehow());

const { port1, port2 } = new MessageChannel();

port1.onmessage = ({ data }) => {
  data.getReader().read().then((chunk) => {
    console.log(chunk);
  });
};

port2.postMessage(stream, [stream]);

[object Object]

• iterable <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterable_protocol" class="type"><Iterable></a> Object implementing the Symbol.asyncIterator or Symbol.iterator iterable protocol.

A utility method that creates a new <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> from an iterable.

import { ReadableStream } from 'node:stream/web';

async function* asyncIterableGenerator() {
  yield 'a';
  yield 'b';
  yield 'c';
}

const stream = ReadableStream.from(asyncIterableGenerator());

for await (const chunk of stream)
  console.log(chunk); // Prints: 'a', 'b', 'c'

const { ReadableStream } = require('node:stream/web');

async function* asyncIterableGenerator() {
  yield 'a';
  yield 'b';
  yield 'c';
}

(async () => {
  const stream = ReadableStream.from(asyncIterableGenerator());

  for await (const chunk of stream)
    console.log(chunk); // Prints: 'a', 'b', 'c'
})();

To pipe the resulting <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> into a <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> the <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterable_protocol" class="type"><Iterable></a> should yield a sequence of <a href="buffer.html#class-buffer" class="type"><Buffer></a>, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a>, or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> objects.

import { ReadableStream } from 'node:stream/web';
import { Buffer } from 'node:buffer';

async function* asyncIterableGenerator() {
  yield Buffer.from('a');
  yield Buffer.from('b');
  yield Buffer.from('c');
}

const stream = ReadableStream.from(asyncIterableGenerator());

await stream.pipeTo(createWritableStreamSomehow());

const { ReadableStream } = require('node:stream/web');
const { Buffer } = require('node:buffer');

async function* asyncIterableGenerator() {
  yield Buffer.from('a');
  yield Buffer.from('b');
  yield Buffer.from('c');
}

const stream = ReadableStream.from(asyncIterableGenerator());

(async () => {
  await stream.pipeTo(createWritableStreamSomehow());
})();

[object Object]

By default, calling readableStream.getReader() with no arguments will return an instance of ReadableStreamDefaultReader. The default reader treats the chunks of data passed through the stream as opaque values, which allows the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to work with generally any JavaScript value.

[object Object]

• stream <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>

Creates a new <a href="webstreams.html#class-readablestreamdefaultreader" class="type"><ReadableStreamDefaultReader></a> that is locked to the given <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.

[object Object]

• reason <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
• Returns: A promise fulfilled with undefined.

Cancels the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and returns a promise that is fulfilled when the underlying stream has been canceled.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfilled with undefined when the associated <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> is closed or rejected if the stream errors or the reader's lock is released before the stream finishes closing.

[object Object]

• Returns: A promise fulfilled with an object:
  • value <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
  • done <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a>

Requests the next chunk of data from the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and returns a promise that is fulfilled with the data once it is available.

[object Object]

Releases this reader's lock on the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.

[object Object]

The ReadableStreamBYOBReader is an alternative consumer for byte-oriented <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>s (those that are created with underlyingSource.type set equal to 'bytes' when the ReadableStream was created).

The BYOB is short for "bring your own buffer". This is a pattern that allows for more efficient reading of byte-oriented data that avoids extraneous copying.

import {
  open,
} from 'node:fs/promises';

import {
  ReadableStream,
} from 'node:stream/web';

import { Buffer } from 'node:buffer';

class Source {
  type = 'bytes';
  autoAllocateChunkSize = 1024;

  async start(controller) {
    this.file = await open(new URL(import.meta.url));
    this.controller = controller;
  }

  async pull(controller) {
    const view = controller.byobRequest?.view;
    const {
      bytesRead,
    } = await this.file.read({
      buffer: view,
      offset: view.byteOffset,
      length: view.byteLength,
    });

    if (bytesRead === 0) {
      await this.file.close();
      this.controller.close();
    }
    controller.byobRequest.respond(bytesRead);
  }
}

const stream = new ReadableStream(new Source());

async function read(stream) {
  const reader = stream.getReader({ mode: 'byob' });

  const chunks = [];
  let result;
  do {
    result = await reader.read(Buffer.alloc(100));
    if (result.value !== undefined)
      chunks.push(Buffer.from(result.value));
  } while (!result.done);

  return Buffer.concat(chunks);
}

const data = await read(stream);
console.log(Buffer.from(data).toString());

[object Object]

• stream <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>

Creates a new ReadableStreamBYOBReader that is locked to the given <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.

[object Object]

• reason <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
• Returns: A promise fulfilled with undefined.

Cancels the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and returns a promise that is fulfilled when the underlying stream has been canceled.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfilled with undefined when the associated <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> is closed or rejected if the stream errors or the reader's lock is released before the stream finishes closing.

[object Object]

• view <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a>
• options <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • min <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a> When set, the returned promise will only be fulfilled as soon as min number of elements are available. When not set, the promise fulfills when at least one element is available.
• Returns: A promise fulfilled with an object:
  • value <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a>
  • done <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a>

Requests the next chunk of data from the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and returns a promise that is fulfilled with the data once it is available.

Do not pass a pooled <a href="buffer.html#class-buffer" class="type"><Buffer></a> object instance in to this method. Pooled Buffer objects are created using Buffer.allocUnsafe(), or Buffer.from(), or are often returned by various node:fs module callbacks. These types of Buffers use a shared underlying <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer" class="type"><ArrayBuffer></a> object that contains all of the data from all of the pooled Buffer instances. When a Buffer, <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a>, or <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a> is passed in to readableStreamBYOBReader.read(), the view's underlying ArrayBuffer is detached, invalidating all existing views that may exist on that ArrayBuffer. This can have disastrous consequences for your application.

[object Object]

Releases this reader's lock on the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.

[object Object]

Every <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> has a controller that is responsible for the internal state and management of the stream's queue. The ReadableStreamDefaultController is the default controller implementation for ReadableStreams that are not byte-oriented.

[object Object]

Closes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to which this controller is associated.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

Returns the amount of data remaining to fill the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s queue.

[object Object]

• chunk <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>

Appends a new chunk of data to the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s queue.

[object Object]

• error <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>

Signals an error that causes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to error and close.

[object Object]

Every <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> has a controller that is responsible for the internal state and management of the stream's queue. The ReadableByteStreamController is for byte-oriented ReadableStreams.

[object Object]

• Type: <a href="webstreams.html#class-readablestreambyobrequest" class="type"><ReadableStreamBYOBRequest></a>

[object Object]

Closes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to which this controller is associated.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

Returns the amount of data remaining to fill the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s queue.

[object Object]

• chunk <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a>

Appends a new chunk of data to the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>'s queue.

[object Object]

• error <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>

Signals an error that causes the <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> to error and close.

[object Object]

When using ReadableByteStreamController in byte-oriented streams, and when using the ReadableStreamBYOBReader, the readableByteStreamController.byobRequest property provides access to a ReadableStreamBYOBRequest instance that represents the current read request. The object is used to gain access to the ArrayBuffer/TypedArray that has been provided for the read request to fill, and provides methods for signaling that the data has been provided.

[object Object]

• bytesWritten <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

Signals that a bytesWritten number of bytes have been written to readableStreamBYOBRequest.view.

[object Object]

• view <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a>

Signals that the request has been fulfilled with bytes written to a new Buffer, TypedArray, or DataView.

[object Object]

• Type: <a href="buffer.html#class-buffer" class="type"><Buffer></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray" class="type"><TypedArray></a> | <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/DataView" class="type"><DataView></a>

[object Object]

The WritableStream is a destination to which stream data is sent.

import {
  WritableStream,
} from 'node:stream/web';

const stream = new WritableStream({
  write(chunk) {
    console.log(chunk);
  },
});

await stream.getWriter().write('Hello World');

[object Object]

• underlyingSink <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • start <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked immediately when the WritableStream is created.
    • controller <a href="webstreams.html#class-writablestreamdefaultcontroller" class="type"><WritableStreamDefaultController></a>
    • Returns: undefined or a promise fulfilled with undefined.
  • write <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked when a chunk of data has been written to the WritableStream.
    • chunk <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
    • controller <a href="webstreams.html#class-writablestreamdefaultcontroller" class="type"><WritableStreamDefaultController></a>
    • Returns: A promise fulfilled with undefined.
  • close <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called when the WritableStream is closed.
    • Returns: A promise fulfilled with undefined.
  • abort <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called to abruptly close the WritableStream.
    • reason <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
    • Returns: A promise fulfilled with undefined.
  • type <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> The type option is reserved for future use and must be undefined.
• strategy <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • highWaterMark <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a> The maximum internal queue size before backpressure is applied.
  • size <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each chunk of data.
    • chunk <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
    • Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

[object Object]

• reason <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
• Returns: A promise fulfilled with undefined.

Abruptly terminates the WritableStream. All queued writes will be canceled with their associated promises rejected.

[object Object]

• Returns: A promise fulfilled with undefined.

Closes the WritableStream when no additional writes are expected.

[object Object]

• Returns: <a href="webstreams.html#class-writablestreamdefaultwriter" class="type"><WritableStreamDefaultWriter></a>

Creates and returns a new writer instance that can be used to write data into the WritableStream.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a>

The writableStream.locked property is false by default, and is switched to true while there is an active writer attached to this WritableStream.

[object Object]

A <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> instance can be transferred using a <a href="worker_threads.html#class-messageport" class="type"><MessagePort></a>.

const stream = new WritableStream(getWritableSinkSomehow());

const { port1, port2 } = new MessageChannel();

port1.onmessage = ({ data }) => {
  data.getWriter().write('hello');
};

port2.postMessage(stream, [stream]);

[object Object] [object Object]

• stream <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>

Creates a new WritableStreamDefaultWriter that is locked to the given WritableStream.

[object Object]

• reason <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
• Returns: A promise fulfilled with undefined.

Abruptly terminates the WritableStream. All queued writes will be canceled with their associated promises rejected.

[object Object]

• Returns: A promise fulfilled with undefined.

Closes the WritableStream when no additional writes are expected.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfilled with undefined when the associated <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> is closed or rejected if the stream errors or the writer's lock is released before the stream finishes closing.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

The amount of data required to fill the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>'s queue.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfilled with undefined when the writer is ready to be used.

[object Object]

Releases this writer's lock on the underlying <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>.

[object Object]

• chunk <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
• Returns: A promise fulfilled with undefined.

Appends a new chunk of data to the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>'s queue.

[object Object]

The WritableStreamDefaultController manages the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>'s internal state.

[object Object]

• error <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>

Called by user-code to signal that an error has occurred while processing the WritableStream data. When called, the <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> will be aborted, with currently pending writes canceled.

[object Object]

• Type: <a href="globals.html#class-abortsignal" class="type"><AbortSignal></a> An AbortSignal that can be used to cancel pending write or close operations when a <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> is aborted.

[object Object]

A TransformStream consists of a <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> and a <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a> that are connected such that the data written to the WritableStream is received, and potentially transformed, before being pushed into the ReadableStream's queue.

import {
  TransformStream,
} from 'node:stream/web';

const transform = new TransformStream({
  transform(chunk, controller) {
    controller.enqueue(chunk.toUpperCase());
  },
});

await Promise.all([
  transform.writable.getWriter().write('A'),
  transform.readable.getReader().read(),
]);

[object Object]

• transformer <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • start <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is invoked immediately when the TransformStream is created.
    • controller <a href="webstreams.html#class-transformstreamdefaultcontroller" class="type"><TransformStreamDefaultController></a>
    • Returns: undefined or a promise fulfilled with undefined
  • transform <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that receives, and potentially modifies, a chunk of data written to transformStream.writable, before forwarding that on to transformStream.readable.
    • chunk <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
    • controller <a href="webstreams.html#class-transformstreamdefaultcontroller" class="type"><TransformStreamDefaultController></a>
    • Returns: A promise fulfilled with undefined.
  • flush <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called immediately before the writable side of the TransformStream is closed, signaling the end of the transformation process.
    • controller <a href="webstreams.html#class-transformstreamdefaultcontroller" class="type"><TransformStreamDefaultController></a>
    • Returns: A promise fulfilled with undefined.
  • cancel <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function that is called when either the readable side of the TransformStream is canceled or the writable side is aborted.
    • reason <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
    • Returns: A promise fulfilled with undefined.
  • readableType <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the readableType option is reserved for future use and must be undefined.
  • writableType <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a> the writableType option is reserved for future use and must be undefined.
• writableStrategy <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • highWaterMark <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a> The maximum internal queue size before backpressure is applied.
  • size <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each chunk of data.
    • chunk <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
    • Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>
• readableStrategy <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • highWaterMark <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a> The maximum internal queue size before backpressure is applied.
  • size <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a> A user-defined function used to identify the size of each chunk of data.
    • chunk <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
    • Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

[object Object]

• Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>

[object Object]

• Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>

[object Object]

A <a href="webstreams.html#class-transformstream" class="type"><TransformStream></a> instance can be transferred using a <a href="worker_threads.html#class-messageport" class="type"><MessagePort></a>.

const stream = new TransformStream();

const { port1, port2 } = new MessageChannel();

port1.onmessage = ({ data }) => {
  const { writable, readable } = data;
  // ...
};

port2.postMessage(stream, [stream]);

[object Object]

The TransformStreamDefaultController manages the internal state of the TransformStream.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

The amount of data required to fill the readable side's queue.

[object Object]

• chunk <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>

Appends a chunk of data to the readable side's queue.

[object Object]

• reason <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>

Signals to both the readable and writable side that an error has occurred while processing the transform data, causing both sides to be abruptly closed.

[object Object]

Closes the readable side of the transport and causes the writable side to be abruptly closed with an error.

[object Object] [object Object]

• init <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • highWaterMark <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a>
  • chunk <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
  • Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

[object Object] [object Object]

• init <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • highWaterMark <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function" class="type"><Function></a>
  • chunk <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Data_types" class="type"><any></a>
  • Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#number_type" class="type"><number></a>

[object Object] [object Object]

Creates a new TextEncoderStream instance.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#string_type" class="type"><string></a>

The encoding supported by the TextEncoderStream instance.

[object Object]

• Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>

[object Object]

• Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>

[object Object] [object Object]

• encoding <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#string_type" class="type"><string></a> Identifies the encoding that this TextDecoder instance supports. Default: 'utf-8'.
• options <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object" class="type"><Object></a>
  • fatal <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a> true if decoding failures are fatal.
  • ignoreBOM <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a> When true, the TextDecoderStream will include the byte order mark in the decoded result. When false, the byte order mark will be removed from the output. This option is only used when encoding is 'utf-8', 'utf-16be', or 'utf-16le'. Default: false.

Creates a new TextDecoderStream instance.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#string_type" class="type"><string></a>

The encoding supported by the TextDecoderStream instance.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a>

The value will be true if decoding errors result in a TypeError being thrown.

[object Object]

• Type: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#boolean_type" class="type"><boolean></a>

The value will be true if the decoding result will include the byte order mark.

[object Object]

• Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>

[object Object]

• Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>

[object Object] [object Object]

• format <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#string_type" class="type"><string></a> One of 'deflate', 'deflate-raw', 'gzip', or 'brotli'.

[object Object]

• Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>

[object Object]

• Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>

[object Object] [object Object]

• format <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#string_type" class="type"><string></a> One of 'deflate', 'deflate-raw', 'gzip', or 'brotli'.

[object Object]

• Type: <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a>

[object Object]

• Type: <a href="webstreams.html#class-writablestream" class="type"><WritableStream></a>

[object Object]

The utility consumer functions provide common options for consuming streams.

They are accessed using:

import {
  arrayBuffer,
  blob,
  buffer,
  json,
  text,
} from 'node:stream/consumers';

const {
  arrayBuffer,
  blob,
  buffer,
  json,
  text,
} = require('node:stream/consumers');

[object Object]

• stream <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> | <a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://tc39.github.io/ecma262/#sec-asynciterator-interface" class="type"><AsyncIterator></a>
• Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with an ArrayBuffer containing the full contents of the stream.

import { arrayBuffer } from 'node:stream/consumers';
import { Readable } from 'node:stream';
import { TextEncoder } from 'node:util';

const encoder = new TextEncoder();
const dataArray = encoder.encode('hello world from consumers!');

const readable = Readable.from(dataArray);
const data = await arrayBuffer(readable);
console.log(`from readable: ${data.byteLength}`);
// Prints: from readable: 76

const { arrayBuffer } = require('node:stream/consumers');
const { Readable } = require('node:stream');
const { TextEncoder } = require('node:util');

const encoder = new TextEncoder();
const dataArray = encoder.encode('hello world from consumers!');
const readable = Readable.from(dataArray);
arrayBuffer(readable).then((data) => {
  console.log(`from readable: ${data.byteLength}`);
  // Prints: from readable: 76
});

[object Object]

• stream <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> | <a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://tc39.github.io/ecma262/#sec-asynciterator-interface" class="type"><AsyncIterator></a>
• Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with a <a href="buffer.html#class-blob" class="type"><Blob></a> containing the full contents of the stream.

import { blob } from 'node:stream/consumers';

const dataBlob = new Blob(['hello world from consumers!']);

const readable = dataBlob.stream();
const data = await blob(readable);
console.log(`from readable: ${data.size}`);
// Prints: from readable: 27

const { blob } = require('node:stream/consumers');

const dataBlob = new Blob(['hello world from consumers!']);

const readable = dataBlob.stream();
blob(readable).then((data) => {
  console.log(`from readable: ${data.size}`);
  // Prints: from readable: 27
});

[object Object]

• stream <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> | <a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://tc39.github.io/ecma262/#sec-asynciterator-interface" class="type"><AsyncIterator></a>
• Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with a <a href="buffer.html#class-buffer" class="type"><Buffer></a> containing the full contents of the stream.

import { buffer } from 'node:stream/consumers';
import { Readable } from 'node:stream';
import { Buffer } from 'node:buffer';

const dataBuffer = Buffer.from('hello world from consumers!');

const readable = Readable.from(dataBuffer);
const data = await buffer(readable);
console.log(`from readable: ${data.length}`);
// Prints: from readable: 27

const { buffer } = require('node:stream/consumers');
const { Readable } = require('node:stream');
const { Buffer } = require('node:buffer');

const dataBuffer = Buffer.from('hello world from consumers!');

const readable = Readable.from(dataBuffer);
buffer(readable).then((data) => {
  console.log(`from readable: ${data.length}`);
  // Prints: from readable: 27
});

[object Object]

• stream <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> | <a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://tc39.github.io/ecma262/#sec-asynciterator-interface" class="type"><AsyncIterator></a>
• Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with a <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array" class="type"><Uint8Array></a> containing the full contents of the stream.

import { bytes } from 'node:stream/consumers';
import { Readable } from 'node:stream';
import { Buffer } from 'node:buffer';

const dataBuffer = Buffer.from('hello world from consumers!');

const readable = Readable.from(dataBuffer);
const data = await bytes(readable);
console.log(`from readable: ${data.length}`);
// Prints: from readable: 27

const { bytes } = require('node:stream/consumers');
const { Readable } = require('node:stream');
const { Buffer } = require('node:buffer');

const dataBuffer = Buffer.from('hello world from consumers!');

const readable = Readable.from(dataBuffer);
bytes(readable).then((data) => {
  console.log(`from readable: ${data.length}`);
  // Prints: from readable: 27
});

[object Object]

• stream <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> | <a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://tc39.github.io/ecma262/#sec-asynciterator-interface" class="type"><AsyncIterator></a>
• Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with the contents of the stream parsed as a UTF-8 encoded string that is then passed through JSON.parse().

import { json } from 'node:stream/consumers';
import { Readable } from 'node:stream';

const items = Array.from(
  {
    length: 100,
  },
  () => ({
    message: 'hello world from consumers!',
  }),
);

const readable = Readable.from(JSON.stringify(items));
const data = await json(readable);
console.log(`from readable: ${data.length}`);
// Prints: from readable: 100

const { json } = require('node:stream/consumers');
const { Readable } = require('node:stream');

const items = Array.from(
  {
    length: 100,
  },
  () => ({
    message: 'hello world from consumers!',
  }),
);

const readable = Readable.from(JSON.stringify(items));
json(readable).then((data) => {
  console.log(`from readable: ${data.length}`);
  // Prints: from readable: 100
});

[object Object]

• stream <a href="webstreams.html#class-readablestream" class="type"><ReadableStream></a> | <a href="stream.html#class-streamreadable" class="type"><stream.Readable></a> | <a href="https://tc39.github.io/ecma262/#sec-asynciterator-interface" class="type"><AsyncIterator></a>
• Returns: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise" class="type"><Promise></a> Fulfills with the contents of the stream parsed as a UTF-8 encoded string.

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

const readable = Readable.from('Hello world from consumers!');
const data = await text(readable);
console.log(`from readable: ${data.length}`);
// Prints: from readable: 27

const { text } = require('node:stream/consumers');
const { Readable } = require('node:stream');

const readable = Readable.from('Hello world from consumers!');
text(readable).then((data) => {
  console.log(`from readable: ${data.length}`);
  // Prints: from readable: 27
});