base64-js 1.5.1: toByteArray

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify toByteArray in pkg:npm/base64-js@1.5.1
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/base64-js@1.5.1
Demonstrate these symbols/APIs:
  - toByteArray

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:a76a7b735cffb1498525dc32c4ec7f165cee9615783f7a08cffeb2b6c045cf4c","contract":["toByteArray decodes standard base64 string into Uint8Array","toByteArray decodes base64 string with double padding into Uint8Array","toByteArray decodes base64 string with single padding into Uint8Array","toByteArray decodes url-safe base64 string containing dash and underscore","toByteArray returns empty Uint8Array for empty string","toByteArray throws Error when base64 string length is not a multiple of 4"],"goal":"verify toByteArray in pkg:npm/base64-js@1.5.1","kind":"HOW","packages":["pkg:npm/base64-js@1.5.1"],"schemaVersion":1,"symbols":["toByteArray"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/base64-js@1.5.1"],"schemaVersion":1,"subject":"pkg:npm/base64-js@1.5.1","symbols":["toByteArray"],"verifierAdapter":"node-typescript@1"}

{
  "name": "base64-js-verification",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "base64-js-verification",
      "version": "1.0.0",
      "dependencies": {
        "base64-js": "1.5.1"
      }
    },
    "node_modules/base64-js": {
      "version": "1.5.1",
      "resolved": "https://registry.npmjs.org/base64-js/-/base64-js-1.5.1.tgz",
      "integrity": "sha512-AKpaYlHn8t4SVbOHCy+b5+KKgvR4vrsD8vbvrbiQJps7fKDTkjkDry6ji0rUJjC0kzbNePLwzxq8iypo41qeWA==",
      "funding": [
        {
          "type": "github",
          "url": "https://github.com/sponsors/feross"
        },
        {
          "type": "patreon",
          "url": "https://www.patreon.com/feross"
        },
        {
          "type": "consulting",
          "url": "https://feross.org/support"
        }
      ],
      "license": "MIT"
    }
  }
}

{
  "name": "base64-js-verification",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification for base64-js toByteArray",
  "dependencies": {
    "base64-js": "1.5.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify toByteArray in pkg:npm/base64-js@1.5.1",
  "kind": "HOW",
  "packages": [
    "pkg:npm/base64-js@1.5.1"
  ],
  "symbols": [
    "toByteArray"
  ]
}

import assert from 'node:assert';
import base64 from 'base64-js';

const { toByteArray } = base64;

// 1. toByteArray decodes standard base64 string into Uint8Array
const standardBytes = toByteArray('Zm9vYmFy');
assert.ok(standardBytes instanceof Uint8Array);
assert.strictEqual(standardBytes.length, 6);
assert.deepStrictEqual(Array.from(standardBytes), [102, 111, 111, 98, 97, 114]);

// 2. toByteArray decodes base64 string with double padding into Uint8Array
const doublePadded = toByteArray('AQ==');
assert.ok(doublePadded instanceof Uint8Array);
assert.strictEqual(doublePadded.length, 1);
assert.deepStrictEqual(Array.from(doublePadded), [1]);

// 3. toByteArray decodes base64 string with single padding into Uint8Array
const singlePadded = toByteArray('AQI=');
assert.ok(singlePadded instanceof Uint8Array);
assert.strictEqual(singlePadded.length, 2);
assert.deepStrictEqual(Array.from(singlePadded), [1, 2]);

// 4. toByteArray decodes url-safe base64 string containing dash and underscore
const urlSafeBytes = toByteArray('-_8=');
assert.ok(urlSafeBytes instanceof Uint8Array);
assert.strictEqual(urlSafeBytes.length, 2);
assert.deepStrictEqual(Array.from(urlSafeBytes), [0xFB, 0xFF]);

// 5. toByteArray returns empty Uint8Array for empty string
const emptyBytes = toByteArray('');
assert.ok(emptyBytes instanceof Uint8Array);
assert.strictEqual(emptyBytes.length, 0);

// 6. toByteArray throws Error when base64 string length is not a multiple of 4
assert.throws(
  () => toByteArray('abc'),
  {
    name: 'Error',
    message: 'Invalid string. Length must be a multiple of 4'
  }
);