#442 Deep Clone

medium
javascript

Implement a deepClone utility that returns a deep-copied version of any plain JavaScript data (objects, arrays, and primitives).

Signature

function deepClone<T>(value: T): T

Requirements

  1. Supported inputs:
    • Primitives (string, number, boolean, null, undefined, bigint, symbol)
    • Plain objects (created with {} or Object.create(null))
    • Arrays
  2. For objects and arrays, every nested level must be cloned by value, never by reference.
  3. Any value that is not a primitive, plain object, or array (e.g. Date, RegExp, Map, Set, functions, DOM nodes) should be returned as-is (shared reference).
  4. Circular references are out of scope (you may assume the input is acyclic).

Example

const original = {
  user: "Alice",
  scores: [1, 2, 3],
};

const copy = deepClone(original);
copy.scores.push(4);

console.log(original.scores); // [1, 2, 3]
console.log(copy.scores);    // [1, 2, 3, 4]