Convert an ArrayBuffer
An ArrayBuffer is a chunk of raw memory with no read or write interface of its own. To use one returned by fetch, the Web Crypto API, or a file read, you usually convert it to a view or another type first. This example shows the common conversions.
We start with an ArrayBuffer containing the bytes of the string "Hello".
const buffer = new TextEncoder().encode("Hello").buffer as ArrayBuffer;To convert to a Uint8Array, wrap the buffer in a view. This does not copy the bytes. The view reads and writes the same memory.
const bytes = new Uint8Array(buffer);
console.log(bytes); // Uint8Array(5) [ 72, 101, 108, 108, 111 ]For an independent copy instead of a shared view, slice the buffer first.
const copy = new Uint8Array(buffer.slice(0));
console.log(copy.buffer !== buffer); // trueTo convert to a string, decode the bytes with TextDecoder. It accepts an ArrayBuffer directly.
const text = new TextDecoder().decode(buffer);
console.log(text); // HelloTo get a plain array of numbers, create a view and copy it into an array.
const numbers = Array.from(new Uint8Array(buffer));
console.log(numbers); // [ 72, 101, 108, 108, 111 ]To convert to a Blob, pass the buffer in the parts list of the Blob constructor. The optional type option sets the MIME type.
const blob = new Blob([buffer], { type: "text/plain" });
console.log(blob.size); // 5A DataView reads and writes numeric types at specific byte offsets, with explicit endianness.
const view = new DataView(buffer);
console.log(view.getUint8(0)); // 72When working with Node.js APIs, Buffer.from creates a Buffer viewing the same memory, just like Uint8Array does.
import { Buffer } from "node:buffer";
const nodeBuffer = Buffer.from(buffer);
console.log(nodeBuffer.toString("utf8")); // HelloRun this example locally using the Deno CLI:
deno run https://docs.deno.com/examples/scripts/convert_arraybuffer.ts