sqids 0.3.0: decode

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 decode in pkg:npm/sqids@0.3.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/sqids@0.3.0
Demonstrate these symbols/APIs:
  - decode

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:sha256:4871211a9ecd3a509bd398d0f40ab5534b4b912145f9c4f17077712c5818db3b","contract":["decode decodes an encoded ID back to the original array of numbers","decode returns an empty array when decoding an empty string","decode returns an empty array when ID contains characters outside the alphabet","decode correctly decodes IDs generated with custom alphabet","decode correctly decodes IDs generated with custom minLength padding","decode accurately decodes multiple numbers and single numbers"],"goal":"verify decode in pkg:npm/sqids@0.3.0","kind":"HOW","packages":["pkg:npm/sqids@0.3.0"],"schemaVersion":1,"symbols":["decode"]},"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/sqids@0.3.0"],"schemaVersion":1,"subject":"pkg:npm/sqids@0.3.0","symbols":["decode"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-sqids-decode",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-sqids-decode",
      "version": "1.0.0",
      "dependencies": {
        "sqids": "0.3.0"
      }
    },
    "node_modules/sqids": {
      "version": "0.3.0",
      "resolved": "https://registry.npmjs.org/sqids/-/sqids-0.3.0.tgz",
      "integrity": "sha512-lOQK1ucVg+W6n3FhRwwSeUijxe93b51Bfz5PMRMihVf1iVkl82ePQG7V5vwrhzB11v0NtsR25PSZRGiSomJaJw==",
      "license": "MIT"
    }
  }
}

{
  "name": "sample-sqids-decode",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification of decode in sqids",
  "type": "module",
  "main": "src/index.js",
  "dependencies": {
    "sqids": "0.3.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify decode in pkg:npm/sqids@0.3.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/sqids@0.3.0"
  ],
  "symbols": [
    "decode"
  ]
}

import Sqids from 'sqids';

/**
 * Creates a new Sqids instance with optional configuration.
 * @param {object} [options]
 * @param {string} [options.alphabet]
 * @param {number} [options.minLength]
 * @param {string[]|Set<string>} [options.blocklist]
 * @returns {Sqids}
 */
export function createSqids(options) {
  return new Sqids(options);
}

/**
 * Decodes a Sqids ID into an array of numbers using the provided or default Sqids instance.
 * @param {string} id
 * @param {object} [options]
 * @returns {number[]}
 */
export function decodeId(id, options) {
  const instance = new Sqids(options);
  return instance.decode(id);
}

export { Sqids };
export default Sqids;

import assert from 'node:assert/strict';
import Sqids, { createSqids, decodeId } from '../src/index.js';

// 1. decode decodes an encoded ID back to the original array of numbers
const sqids = createSqids();
const numbers = [1, 2, 3];
const id = sqids.encode(numbers);
const decoded = sqids.decode(id);
assert.deepStrictEqual(decoded, numbers, 'decode must return original numbers array');

const helperDecoded = decodeId(id);
assert.deepStrictEqual(helperDecoded, numbers, 'decodeId helper must return original numbers array');

// 2. decode returns an empty array when decoding an empty string
assert.deepStrictEqual(sqids.decode(''), [], 'decoding empty string must return empty array');
assert.deepStrictEqual(decodeId(''), [], 'helper decoding empty string must return empty array');

// 3. decode returns an empty array when ID contains characters outside the alphabet
assert.deepStrictEqual(sqids.decode('!@#$%^&*()'), [], 'decoding string with invalid characters must return empty array');
assert.deepStrictEqual(decodeId('!@#$%^&*()'), [], 'helper decoding string with invalid characters must return empty array');

// 4. decode correctly decodes IDs generated with custom alphabet
const customAlphabetSqids = createSqids({
  alphabet: 'abcdefghijklmnopqrstuvwxyz0123456789',
});
const customNumbers = [42, 99, 1000];
const customId = customAlphabetSqids.encode(customNumbers);
assert.deepStrictEqual(
  customAlphabetSqids.decode(customId),
  customNumbers,
  'decode with custom alphabet must reproduce numbers'
);
assert.deepStrictEqual(
  decodeId(customId, { alphabet: 'abcdefghijklmnopqrstuvwxyz0123456789' }),
  customNumbers,
  'helper decodeId with custom alphabet options must reproduce numbers'
);

// 5. decode correctly decodes IDs generated with custom minLength padding
const paddedSqids = createSqids({ minLength: 10 });
const paddedNumbers = [7, 8, 9];
const paddedId = paddedSqids.encode(paddedNumbers);
assert.ok(paddedId.length >= 10, 'padded ID length must satisfy minLength');
assert.deepStrictEqual(
  paddedSqids.decode(paddedId),
  paddedNumbers,
  'decode must correctly unpack padded IDs'
);
assert.deepStrictEqual(
  decodeId(paddedId, { minLength: 10 }),
  paddedNumbers,
  'helper decodeId must correctly unpack padded IDs'
);

// 6. decode accurately decodes multiple numbers and single numbers
const singleNum = [12345];
const singleId = sqids.encode(singleNum);
assert.deepStrictEqual(sqids.decode(singleId), singleNum, 'decode single number');

const multiNums = [0, 1, 10, 100, 1000, 10000];
const multiId = sqids.encode(multiNums);
assert.deepStrictEqual(sqids.decode(multiId), multiNums, 'decode multiple numbers');

console.log('sqids decode contract tests passed successfully.');