get-stream

Get a stream as a string, Buffer, ArrayBuffer or array

Features

• Works in any JavaScript environment (Node.js, browsers, etc.).
• Supports text streams, binary streams and object streams.
• Supports async iterables.
• Can set a maximum stream size.
• Returns partially read data when the stream errors.
• Fast.

Install

npm install get-stream

Usage

Node.js streams

import fs from 'node:fs';
import getStream from 'get-stream';

const stream = fs.createReadStream('unicorn.txt');

console.log(await getStream(stream));
/*
              ,,))))))));,
           __)))))))))))))),
\|/       -\(((((''''((((((((.
-*-==//////((''  .     `)))))),
/|\      ))| o    ;-.    '(((((                                  ,(,
         ( `|    /  )    ;))))'                               ,_))^;(~
            |   |   |   ,))((((_     _____------~~~-.        %,;(;(>';'~
            o_);   ;    )))(((` ~---~  `::           \      %%~~)(v;(`('~
                  ;    ''''````         `:       `:::|\,__,%%    );`'; ~
                 |   _                )     /      `:|`----'     `-'
           ______/\/~    |                 /        /
         /~;;.____/;;'  /          ___--,-(   `;;;/
        / //  _;______;'------~~~~~    /;;/\    /
       //  | |                        / ;   \;;,\
      (<_  | ;                      /',/-----'  _>
       \_| ||_                     //~;~~~~~~~~~
           `\_|                   (,~~
                                   \~\
                                    ~~
*/

Web streams

import getStream from 'get-stream';

const {body: readableStream} = await fetch('https://example.com');
console.log(await getStream(readableStream));

This works in any browser, even the ones not supporting ReadableStream.values() yet.

Async iterables

import {opendir} from 'node:fs/promises';
import {getStreamAsArray} from 'get-stream';

const asyncIterable = await opendir(directory);
console.log(await getStreamAsArray(asyncIterable));

API

The following methods read the stream's contents and return it as a promise.

getStream(stream, options?)

stream: stream.Readable, ReadableStream, or AsyncIterable<string | Buffer | ArrayBuffer | DataView | TypedArray>
options: Options

Get the given stream as a string.

getStreamAsBuffer(stream, options?)

Get the given stream as a Node.js Buffer.

import {getStreamAsBuffer} from 'get-stream';

const stream = fs.createReadStream('unicorn.png');
console.log(await getStreamAsBuffer(stream));

getStreamAsArrayBuffer(stream, options?)

Get the given stream as an ArrayBuffer.

import {getStreamAsArrayBuffer} from 'get-stream';

const {body: readableStream} = await fetch('https://example.com');
console.log(await getStreamAsArrayBuffer(readableStream));

getStreamAsArray(stream, options?)

Get the given stream as an array. Unlike other methods, this supports streams of objects.

import {getStreamAsArray} from 'get-stream';

const {body: readableStream} = await fetch('https://example.com');
console.log(await getStreamAsArray(readableStream));

options

Type: object

maxBuffer

Type: number
Default: Infinity

Maximum length of the stream. If exceeded, the promise will be rejected with a MaxBufferError.

Depending on the method, the length is measured with string.length, buffer.length, arrayBuffer.byteLength or array.length.

Errors

If the stream errors, the returned promise will be rejected with the error. Any contents already read from the stream will be set to error.bufferedData, which is a string, a Buffer, an ArrayBuffer or an array depending on the method used.

import getStream from 'get-stream';

try {
	await getStream(streamThatErrorsAtTheEnd('unicorn'));
} catch (error) {
	console.log(error.bufferedData);
	//=> 'unicorn'
}

Browser support

For this module to work in browsers, a bundler must be used that either:

• Supports the exports.browser field in package.json
• Strips or ignores node:* imports

Most bundlers (such as Webpack) support either of these.

Additionally, browsers support web streams and async iterables, but not Node.js streams.

Tips

Alternatives

If you do not need the maxBuffer option, error.bufferedData, nor browser support, you can use the following methods instead of this package.

streamConsumers.text()

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

const stream = fs.createReadStream('unicorn.txt', {encoding: 'utf8'});
console.log(await text(stream))

streamConsumers.buffer()

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

console.log(await buffer(stream))

streamConsumers.arrayBuffer()

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

console.log(await arrayBuffer(stream))

readable.toArray()

console.log(await stream.toArray())

Array.fromAsync()

If your environment supports it:

console.log(await Array.fromAsync(stream))

Non-UTF-8 encoding

When all of the following conditions apply:

• getStream() is used (as opposed to getStreamAsBuffer() or getStreamAsArrayBuffer())
• The stream is binary (not text)
• The stream's encoding is not UTF-8 (for example, it is UTF-16, hexadecimal, or Base64)

Then the stream must be decoded using a transform stream like TextDecoderStream or b64.

import getStream from 'get-stream';

const textDecoderStream = new TextDecoderStream('utf-16le');
const {body: readableStream} = await fetch('https://example.com');
console.log(await getStream(readableStream.pipeThrough(textDecoderStream)));

Blobs

getStreamAsArrayBuffer() can be used to create Blobs.

import {getStreamAsArrayBuffer} from 'get-stream';

const stream = fs.createReadStream('unicorn.txt');
console.log(new Blob([await getStreamAsArrayBuffer(stream)]));

JSON streaming

getStreamAsArray() can be combined with JSON streaming utilities to parse JSON incrementally.

import fs from 'node:fs';
import {compose as composeStreams} from 'node:stream';
import {getStreamAsArray} from 'get-stream';
import streamJson from 'stream-json';
import streamJsonArray from 'stream-json/streamers/StreamArray.js';

const stream = fs.createReadStream('big-array-of-objects.json');
console.log(await getStreamAsArray(
	composeStreams(stream, streamJson.parser(), streamJsonArray.streamArray()),
));

Benchmarks

Node.js stream (100 MB, binary)

• getStream(): 142ms
• text(): 139ms
• getStreamAsBuffer(): 106ms
• buffer(): 83ms
• getStreamAsArrayBuffer(): 105ms
• arrayBuffer(): 81ms
• getStreamAsArray(): 24ms
• stream.toArray(): 21ms

Node.js stream (100 MB, text)

• getStream(): 90ms
• text(): 89ms
• getStreamAsBuffer(): 127ms
• buffer(): 192ms
• getStreamAsArrayBuffer(): 129ms
• arrayBuffer(): 195ms
• getStreamAsArray(): 89ms
• stream.toArray(): 90ms

Web ReadableStream (100 MB, binary)

• getStream(): 223ms
• text(): 221ms
• getStreamAsBuffer(): 182ms
• buffer(): 153ms
• getStreamAsArrayBuffer(): 171ms
• arrayBuffer(): 155ms
• getStreamAsArray(): 83ms

Web ReadableStream (100 MB, text)

• getStream(): 141ms
• text(): 139ms
• getStreamAsBuffer(): 91ms
• buffer(): 80ms
• getStreamAsArrayBuffer(): 89ms
• arrayBuffer(): 81ms
• getStreamAsArray(): 21ms

Benchmarks' source file.

FAQ

How is this different from concat-stream?

This module accepts a stream instead of being one and returns a promise instead of using a callback. The API is simpler and it only supports returning a string, Buffer, an ArrayBuffer or an array. It doesn't have a fragile type inference. You explicitly choose what you want. And it doesn't depend on the huge readable-stream package.

Related

• get-stdin - Get stdin as a string or buffer
• into-stream - The opposite of this package