Here are the most reliable ways to perform a deep clone of an object in JavaScript.
✅ Structured Clone (Modern & Robust)
Supports functions, dates, maps, sets, circular references, etc.
const deepClone = structuredClone(original);
✅ Fast and standard.
❌ Not supported in older environments (e.g., Node <17, legacy browsers).
✅ 2. Lodash cloneDeep
import cloneDeep from 'lodash/cloneDeep'; const deepClone = cloneDeep(original);
✅ Handles most edge cases.
✅ Works in all JS environments.
❌ Requires external dependency.
⚠️ 3. Manual Recursion (Custom Deep Clone)
For full control; avoid unless necessary.
function deepClone(obj, hash = new WeakMap()) { if (Object(obj) !== obj || obj instanceof Function) return obj; if (hash.has(obj)) return hash.get(obj); // handle circular refs const result = Array.isArray(obj) ? [] : obj instanceof Date ? new Date(obj) : obj instanceof RegExp ? new RegExp(obj.source, obj.flags) : Object.create(Object.getPrototypeOf(obj)); hash.set(obj, result); for (const key of Reflect.ownKeys(obj)) { result[key] = deepClone(obj[key], hash); } return result; } // or more simply: function deepCopy(obj) { if (obj === null || typeof obj !== 'object') return obj; const newObj = Array.isArray(obj) ? [] : {}; for (const key of Object.keys(obj)) { newObj[key] = deepCopy(obj[key]); } return newObj; }
✅ Fine-grained control.
❌ Error-prone, needs frequent updates for edge cases.
⚠️ 4. JSON.parse(JSON.stringify(obj)) (Not Recommended for Complex Objects)
const deepClone = JSON.parse(JSON.stringify(original));
❌ Strips functions,
undefined, symbols, dates, regex, etc.✅ Okay for simple objects only.
Recommendation:
- Use
structuredCloneif environment supports it. - Else use
cloneDeepfrom Lodash. - Use manual recursion only when you need custom behavior.
Let me know your runtime constraints if you want a tailored version.
Quick Quiz
Test your understanding with 3 quick questions
Q1What is a major limitation of using `JSON.parse(JSON.stringify(obj))` for deep cloning?
Q2What is `structuredClone` used for?
Q3Why is a `WeakMap` used in manual deep clone implementations?