lodash 4.18.1: Deep clone complex nested objects, arrays, and custom values preserving reference independence with cloneDeep

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 clone complex nested objects, arrays, and custom values preserving reference independence with cloneDeep
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/lodash@4.18.1
Demonstrate these symbols/APIs:
  - cloneDeep

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:sha256:78f8d5f54f5cd53d644e02d14a8c4ca47319fca9c5dfa8a18163c6065159543a","contract":["cloneDeep recursively clones nested plain objects and arrays into distinct new references","Mutating cloned nested objects or nested arrays does not affect the original source","cloneDeep accurately preserves and copies Date, RegExp, Set, and Map instances with independent contents","cloneDeep correctly preserves circular references and cyclical structures without infinite recursion","cloneDeep returns primitive values directly without modification","cloneDeep accurately clones typed arrays and ArrayBuffer instances"],"goal":"Deep clone complex nested objects, arrays, and custom values preserving reference independence with cloneDeep","kind":"HOW","packages":["pkg:npm/lodash@4.18.1"],"schemaVersion":1,"symbols":["cloneDeep"]},"contractCommand":["node","test/contract.cjs"],"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/lodash@4.18.1"],"schemaVersion":1,"subject":"pkg:npm/lodash@4.18.1","symbols":["cloneDeep"],"verifierAdapter":"node-typescript@1"}

{
  "name": "lodash-clonedeep-verification",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "lodash-clonedeep-verification",
      "version": "1.0.0",
      "dependencies": {
        "lodash": "4.18.1"
      }
    },
    "node_modules/lodash": {
      "version": "4.18.1",
      "resolved": "https://registry.npmjs.org/lodash/-/lodash-4.18.1.tgz",
      "integrity": "sha512-dMInicTPVE8d1e5otfwmmjlxkZoUpiVLwyeTdUsi/Caj/gfzzblBcCE5sRHV/AsjuCmxWrte2TNGSYuCeCq+0Q==",
      "license": "MIT"
    }
  }
}

{
  "name": "lodash-clonedeep-verification",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification for lodash cloneDeep",
  "dependencies": {
    "lodash": "4.18.1"
  }
}

{
  "schemaVersion": 1,
  "goal": "Deep clone complex nested objects, arrays, and custom values preserving reference independence with cloneDeep",
  "kind": "HOW",
  "packages": [
    "pkg:npm/lodash@4.18.1"
  ],
  "symbols": [
    "cloneDeep"
  ]
}

const assert = require('node:assert');
const { cloneDeep } = require('lodash');

// 1. cloneDeep recursively clones nested plain objects and arrays into distinct new references
const original = {
  name: 'CodeSampleX',
  meta: {
    version: 1,
    tags: ['build', 'test']
  },
  counts: [10, 20, [30, 40]]
};

const cloned = cloneDeep(original);
assert.deepStrictEqual(cloned, original);
assert.notStrictEqual(cloned, original);
assert.notStrictEqual(cloned.meta, original.meta);
assert.notStrictEqual(cloned.meta.tags, original.meta.tags);
assert.notStrictEqual(cloned.counts, original.counts);
assert.notStrictEqual(cloned.counts[2], original.counts[2]);

// 2. Mutating cloned nested objects or nested arrays does not affect the original source
cloned.meta.version = 2;
cloned.meta.tags.push('verify');
cloned.counts[2].push(50);

assert.strictEqual(original.meta.version, 1);
assert.deepStrictEqual(original.meta.tags, ['build', 'test']);
assert.deepStrictEqual(original.counts[2], [30, 40]);

// 3. cloneDeep accurately preserves and copies Date, RegExp, Set, and Map instances with independent contents
const date = new Date('2026-08-23T00:00:00.000Z');
const regex = /test-[a-z]+/gi;
const set = new Set(['alpha', 'beta']);
const map = new Map([['key1', { value: 100 }]]);

const complexObj = { date, regex, set, map };
const complexCloned = cloneDeep(complexObj);

assert.ok(complexCloned.date instanceof Date);
assert.strictEqual(complexCloned.date.getTime(), date.getTime());
assert.notStrictEqual(complexCloned.date, date);

assert.ok(complexCloned.regex instanceof RegExp);
assert.strictEqual(complexCloned.regex.source, regex.source);
assert.strictEqual(complexCloned.regex.flags, regex.flags);
assert.notStrictEqual(complexCloned.regex, regex);

assert.ok(complexCloned.set instanceof Set);
assert.strictEqual(complexCloned.set.size, 2);
assert.ok(complexCloned.set.has('alpha'));
assert.notStrictEqual(complexCloned.set, set);
complexCloned.set.add('gamma');
assert.strictEqual(set.has('gamma'), false);

assert.ok(complexCloned.map instanceof Map);
assert.strictEqual(complexCloned.map.size, 1);
assert.notStrictEqual(complexCloned.map, map);
assert.notStrictEqual(complexCloned.map.get('key1'), map.get('key1'));
assert.deepStrictEqual(complexCloned.map.get('key1'), { value: 100 });

// 4. cloneDeep correctly preserves circular references and cyclical structures without infinite recursion
const cyclicObj = { id: 'parent' };
cyclicObj.self = cyclicObj;
cyclicObj.child = { parent: cyclicObj };

const cyclicCloned = cloneDeep(cyclicObj);
assert.strictEqual(cyclicCloned.id, 'parent');
assert.strictEqual(cyclicCloned.self, cyclicCloned);
assert.strictEqual(cyclicCloned.child.parent, cyclicCloned);
assert.notStrictEqual(cyclicCloned, cyclicObj);
assert.notStrictEqual(cyclicCloned.child, cyclicObj.child);

// 5. cloneDeep returns primitive values directly without modification
assert.strictEqual(cloneDeep(42), 42);
assert.strictEqual(cloneDeep('sample-string'), 'sample-string');
assert.strictEqual(cloneDeep(true), true);
assert.strictEqual(cloneDeep(null), null);
assert.strictEqual(cloneDeep(undefined), undefined);
const sym = Symbol('token');
assert.strictEqual(cloneDeep(sym), sym);

// 6. cloneDeep accurately clones typed arrays and ArrayBuffer instances
const uint8 = new Uint8Array([1, 2, 3, 4]);
const clonedUint8 = cloneDeep(uint8);
assert.ok(clonedUint8 instanceof Uint8Array);
assert.deepStrictEqual(Array.from(clonedUint8), [1, 2, 3, 4]);
assert.notStrictEqual(clonedUint8, uint8);
clonedUint8[0] = 99;
assert.strictEqual(uint8[0], 1);

console.log('Contract passed');