Blob

A Blob encapsulates immutable, raw data that can be safely shared across multiple worker threads.

new buffer.Blob(sources?, options?): buffer.Blob

Creates a new Blob object containing a concatenation of the given sources.

ArrayBuffer, TypedArray, DataView, and Buffer sources are copied into the 'Blob' and can therefore be safely modified after the 'Blob' is created.

String sources are encoded as UTF-8 byte sequences and copied into the Blob. Unmatched surrogate pairs within each string part will be replaced by Unicode U+FFFD replacement characters.

blob.arrayBuffer(): Promise

Returns a promise that fulfills with an ArrayBuffer containing a copy of the Blob data.

blob.bytes(): Promise

The blob.bytes() method returns the byte of the Blob object as a Promise<Uint8Array>.

const blob = new Blob(['hello']);
blob.bytes().then((bytes) => {
  console.log(bytes); // Outputs: Uint8Array(5) [ 104, 101, 108, 108, 111 ]
});

The total size of the Blob in bytes.

blob.slice(start?, end?, type?): Blob

Creates and returns a new Blob containing a subset of this Blob objects data. The original Blob is not altered.

blob.stream(): ReadableStream

Returns a new ReadableStream that allows the content of the Blob to be read.

blob.text(): Promise

Returns a promise that fulfills with the contents of the Blob decoded as a UTF-8 string.

blob.textStream(): ReadableStream

Returns a new ReadableStream that allows the content of the Blob to be read as a stream of UTF-8 decoded strings. It is equivalent to piping blob.stream() through a TextDecoderStream set up with UTF-8.

The content-type of the Blob.

Once a Blob object is created, it can be sent via MessagePort to multiple destinations without transferring or immediately copying the data. The data contained by the Blob is copied only when the arrayBuffer() or text() methods are called.

import { Blob } from 'node:buffer';
import { setTimeout as delay } from 'node:timers/promises';

const blob = new Blob(['hello there']);

const mc1 = new MessageChannel();
const mc2 = new MessageChannel();

mc1.port1.onmessage = async ({ data }) => {
  console.log(await data.arrayBuffer());
  mc1.port1.close();
};

mc2.port1.onmessage = async ({ data }) => {
  await delay(1000);
  console.log(await data.arrayBuffer());
  mc2.port1.close();
};

mc1.port2.postMessage(blob);
mc2.port2.postMessage(blob);

// The Blob is still usable after posting.
blob.text().then(console.log);

const { Blob } = require('node:buffer');
const { setTimeout: delay } = require('node:timers/promises');

const blob = new Blob(['hello there']);

const mc1 = new MessageChannel();
const mc2 = new MessageChannel();

mc1.port1.onmessage = async ({ data }) => {
  console.log(await data.arrayBuffer());
  mc1.port1.close();
};

mc2.port1.onmessage = async ({ data }) => {
  await delay(1000);
  console.log(await data.arrayBuffer());
  mc2.port1.close();
};

mc1.port2.postMessage(blob);
mc2.port2.postMessage(blob);

// The Blob is still usable after posting.
blob.text().then(console.log);