How to Copy an Object in JavaScript?

In JavaScript, object copying can be:

• Shallow copy — only top-level properties are copied, nested objects are copied by reference.
• Deep copy — a complete independent copy is created, including nested objects and arrays.

Shallow Copying

Spread Operator "(...)"

const obj = { name: "Alice", age: 25 };
const copy = { ...obj };

• Simple and readable
• Only top level is copied

Object.assign()

const obj = { name: "Bob" };
const copy = Object.assign({}, obj);

• Alternative to spread
• Also shallow copy

Deep Copying

JSON.parse(JSON.stringify(...))

const original = { user: { name: "Tom" } };
const deepCopy = JSON.parse(JSON.stringify(original));

• Convenient and simple
• Doesn't copy functions, undefined, Date, Map, Set, etc.

structuredClone() (built-in method)

const deepCopy = structuredClone(obj);

• Works with most structures (including Map, Set, Date, Blob)
• Safe and efficient
• Requires browser support (supported in modern browsers)

Manual Copying / Libraries

lodash.cloneDeep

import cloneDeep from 'lodash/cloneDeep';

const deepCopy = cloneDeep(obj);

• Suitable for complex objects
• Proven and reliable method