fast-deep-equal 3.1.3: deep equality comparison of nested objects, arrays, dates, and regexes using fast-deep-equal

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: deep equality comparison of nested objects, arrays, dates, and regexes using fast-deep-equal
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/fast-deep-equal@3.1.3
Demonstrate these symbols/APIs:
  - equal

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:b33e6bbbdd4305ebfa67fe708cd0230749987a6042855da73ad9678f2cb54900","contract":["equal determines deep equality for primitive values and handles NaN equivalence","equal determines deep equality for nested objects regardless of key order","equal determines deep equality for nested arrays and detects mismatched elements or lengths","equal compares Date objects by their getTime value","equal compares RegExp objects by their source pattern and flags"],"goal":"deep equality comparison of nested objects, arrays, dates, and regexes using fast-deep-equal","kind":"HOW","packages":["pkg:npm/fast-deep-equal@3.1.3"],"schemaVersion":1,"symbols":["equal"]},"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/fast-deep-equal@3.1.3"],"schemaVersion":1,"subject":"pkg:npm/fast-deep-equal@3.1.3","symbols":["equal"],"verifierAdapter":"node-typescript@1"}

{
  "name": "fast-deep-equal-verification",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "fast-deep-equal-verification",
      "version": "1.0.0",
      "dependencies": {
        "fast-deep-equal": "3.1.3"
      }
    },
    "node_modules/fast-deep-equal": {
      "version": "3.1.3",
      "resolved": "https://registry.npmjs.org/fast-deep-equal/-/fast-deep-equal-3.1.3.tgz",
      "integrity": "sha512-f3qQ9oQy9j2AhBe/H9VC91wLmKBCCU/gDOnKNAYG5hswO7BLKj09Hc5HYNz9cGI++xlpDCIgDaitVs03ATR84Q==",
      "license": "MIT"
    }
  }
}

{
  "name": "fast-deep-equal-verification",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification for fast-deep-equal",
  "dependencies": {
    "fast-deep-equal": "3.1.3"
  }
}

{
  "schemaVersion": 1,
  "goal": "deep equality comparison of nested objects, arrays, dates, and regexes using fast-deep-equal",
  "kind": "HOW",
  "packages": [
    "pkg:npm/fast-deep-equal@3.1.3"
  ],
  "symbols": [
    "equal"
  ]
}

import assert from 'node:assert';
import equal from 'fast-deep-equal';

// 1. equal determines deep equality for primitive values and handles NaN equivalence
assert.strictEqual(equal(42, 42), true);
assert.strictEqual(equal('hello', 'hello'), true);
assert.strictEqual(equal(true, true), true);
assert.strictEqual(equal(null, null), true);
assert.strictEqual(equal(undefined, undefined), true);
assert.strictEqual(equal(NaN, NaN), true);
assert.strictEqual(equal(42, 43), false);
assert.strictEqual(equal('foo', 'bar'), false);
assert.strictEqual(equal(null, undefined), false);

// 2. equal determines deep equality for nested objects regardless of key order
const objA = { a: 1, b: { c: 'test', d: [10, 20] } };
const objB = { b: { d: [10, 20], c: 'test' }, a: 1 };
const objC = { a: 1, b: { c: 'different', d: [10, 20] } };
assert.strictEqual(equal(objA, objB), true);
assert.strictEqual(equal(objA, objC), false);
assert.strictEqual(equal({ a: 1 }, { a: 1, b: undefined }), false);
assert.strictEqual(equal({ a: 1 }, { b: 1 }), false);

// 3. equal determines deep equality for nested arrays and detects mismatched elements or lengths
const arrA = [1, [2, 3], { key: 'val' }];
const arrB = [1, [2, 3], { key: 'val' }];
const arrC = [1, [2, 4], { key: 'val' }];
const arrD = [1, [2, 3]];
assert.strictEqual(equal(arrA, arrB), true);
assert.strictEqual(equal(arrA, arrC), false);
assert.strictEqual(equal(arrA, arrD), false);
assert.strictEqual(equal([1, 2], { 0: 1, 1: 2 }), false);

// 4. equal compares Date objects by their getTime value
const d1 = new Date('2026-01-01T00:00:00.000Z');
const d2 = new Date('2026-01-01T00:00:00.000Z');
const d3 = new Date('2026-01-02T00:00:00.000Z');
assert.strictEqual(equal(d1, d2), true);
assert.strictEqual(equal(d1, d3), false);

// 5. equal compares RegExp objects by their source pattern and flags
const r1 = /hello[0-9]+/gi;
const r2 = /hello[0-9]+/gi;
const r3 = /hello[0-9]+/g;
const r4 = /world[0-9]+/gi;
assert.strictEqual(equal(r1, r2), true);
assert.strictEqual(equal(r1, r3), false);
assert.strictEqual(equal(r1, r4), false);

console.log('Contract passed');