Manipulating byte arrays

When working with lower-level data we often deal with byte arrays in the form of Uint8Arrays. There are some common manipulations and queries that can be done and are included with the standard library.

Let's initialize some byte arrays

const a = new Uint8Array([0, 1, 2, 3, 4]);
const b = new Uint8Array([5, 6, 7, 8, 9]);
const c = new Uint8Array([4, 5]);

We can concatenate two byte arrays using the concat method

import { concat } from "jsr:@std/bytes/concat";
const d = concat([a, b]);
console.log(d); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Sometimes we need to repeat certain bytes

import { repeat } from "jsr:@std/bytes/repeat";
console.log(repeat(c, 4)); // [4, 5, 4, 5, 4, 5, 4, 5]

Sometimes we need to mutate a Uint8Array and need a copy

import { copy } from "jsr:@std/bytes/copy";
const cpy = new Uint8Array(5);
console.log("Bytes copied:", copy(b, cpy)); // 5
console.log("Bytes:", cpy); // [5, 6, 7, 8, 9]

Run this example locally using the Deno CLI:

deno run https://raw.githubusercontent.com/denoland/deno-docs/main/by-example/byte-manipulation.ts

Additional resources:

Doc: std/bytes