How to make a deep copy of an object? Tell me about structured clone, JSON.stringify, lodash cloneDeep — what are the differences?

Deep copying an object involves creating a new data structure that is completely independent of the original, including nested objects.

JSON.stringify / JSON.parse — the simplest way to deep copy, but with limitations:

• Does not copy functions, undefined, symbols, properties with Symbol type.
• Does not work with objects containing cyclic references (will throw an error).
• Converts dates to strings.

const copy = JSON.parse(JSON.stringify(original));

_.cloneDeep (lodash) — a universal method for deep copying, which:

• Copies almost all data types, including nested objects and arrays.
• Handles cyclic references.
• Does not copy functions (they remain references).

import _ from 'lodash';
const copy = _.cloneDeep(original);

structuredClone — a modern built-in method for deep cloning, supported in browsers and Node.js:

• Works with most data types, including Map, Set, Date, RegExp.
• Supports cyclic references.
• Does not copy functions and some special objects (e.g., DOM elements).
• Faster and more reliable than the JSON method.

const copy = structuredClone(original);

Summary:

• For simple objects without functions and cycles, JSON can be used.
• For complex structures with cycles and various types — lodash cloneDeep or structuredClone.
• structuredClone is the preferred modern method if environment support allows.