Deep Clone Utility

deepClone is a dependency-free TypeScript (ESM) utility that performs a deep copy of any value: nested objects and arrays, built-in types, class instances, sparse arrays, symbol keys, property descriptors (getters/setters, non-enumerable properties) and circular references.

Features

• Deep cloning of objects and arrays, including sparse arrays and non-index array properties.
• Built-in types: Date, RegExp (incl. lastIndex), Set, Map, ArrayBuffer, SharedArrayBuffer, all TypedArrays, DataView, boxed primitives, Error (incl. subclasses and custom properties).
• Prototypes preserved for class instances and objects with arbitrary prototypes (including null).
• Property descriptors preserved: getters/setters, non-enumerable and non-writable properties.
• Symbol keys on both objects and arrays.
• Circular & shared references handled via an internal WeakMap.
• Written in TypeScript with full type definitions.

Installation

npm install js-deep-clone

Usage

import { deepClone } from 'js-deep-clone';
// or: import deepClone from 'js-deep-clone';

const original = {
  name: 'Alice',
  birthDate: new Date(),
  pattern: /hello/gi,
  tags: new Set(['a', 'b']),
  scores: new Map([['math', 5]]),
  friends: ['Bob', 'Charlie'],
};

// Create a circular reference
original.self = original;

const cloned = deepClone(original);

console.log(cloned !== original); // true
console.log(cloned.birthDate instanceof Date); // true
console.log(cloned.self === cloned); // true

Function signature

deepClone<T>(input: T, map?: WeakMap<object, unknown>): T

• input: the value to clone.
• map (optional): Internal WeakMap for circular reference tracking. Exposed only for backward compatibility; do not pass in normal usage.
• Returns a deep copy of the input.

Behavior notes

• Functions are returned as-is (they are not cloneable, this mirrors the original value).
• Unsupported types (DOM nodes, etc.) are cloned as plain objects (not thrown).

Requirements

Node.js 18+ or any modern browser. Pure JavaScript (ES modules).

Running tests

npm install
npm test

Building

npm run build

Development

npm run dev

This starts a Vite dev server with the demo at index.html.

License

MIT