#Utilities

Three standalone helpers are exported for convenience. The library uses them internally; they are exposed because they are handy when working with the same formats by hand.

import { md5, uid, sniffFormat } from 'scratch4js';

#md5(input)

• input: Uint8Array | ArrayBuffer — bytes to hash.
• Returns: string — 32-character lowercase hex digest.

Compute the lowercase hex MD5 digest of some bytes. This is a dependency-free, pure-JS implementation of RFC 1321 that runs identically in Node and the browser. Scratch names asset files by the MD5 of their bytes, which is why the library needs it — and why md5(bytes) matches the assetId of a costume/sound holding those same bytes.

md5(new Uint8Array([1, 2, 3]));
// → '5289df737df57326fcdd22597afb1fac'

#uid()

• Returns: string — a fresh 20-character Scratch-style id.

Generate a unique id drawn from the same character "soup" Scratch uses for blocks, variables, lists and broadcasts, so generated ids look native and stay clear of JSON-unsafe characters. Use it when writing raw blocks or other id-keyed entries by hand.

const id = uid(); // e.g. 'p!Qm,4@z.b{Tn]Wc#3rh'

#sniffFormat(bytes)

• bytes: Uint8Array — the asset contents.
• Returns: string | undefined — the detected dataFormat, or undefined if unknown.

Guess a Scratch dataFormat (file extension) from raw asset bytes by inspecting their leading bytes. Recognises:

This is what lets addCostume and addSound accept a bare buffer without you spelling out dataFormat. When detection fails they fall back to png / wav respectively; pass options.dataFormat to be explicit.

sniffFormat(pngBytes); // 'png'
sniffFormat(unknown); // undefined