What are the different ways to copy an object or an array?
TL;DR
To copy an object or an array in JavaScript, you can use several methods. For shallow copies, you can use the spread operator (...) or Object.assign(). For deep copies, you can use JSON.parse(JSON.stringify()) or libraries like Lodash's _.cloneDeep().
// Shallow copy of an arrayconst originalArray = [1, 2, 3];const shallowCopyArray = [...originalArray];// Shallow copy of an objectconst originalObject = { a: 1, b: 2 };const shallowCopyObject = { ...originalObject };// Deep copy using JSON methodsconst deepCopyObject = JSON.parse(JSON.stringify(originalObject));
Different ways to copy an object or an array
Shallow copy
Using the spread operator
The spread operator (...) is a concise way to create a shallow copy of an array or an object.
// Shallow copy of an arrayconst originalArray = [1, 2, 3];const shallowCopyArray = [...originalArray];// Shallow copy of an objectconst originalObject = { a: 1, b: 2 };const shallowCopyObject = { ...originalObject };
Using Object.assign()
Object.assign() can also be used to create a shallow copy of an object.
const originalObject = { a: 1, b: 2 };const shallowCopyObject = Object.assign({}, originalObject);
Deep copy
Using JSON.parse(JSON.stringify())
This method is a simple way to create a deep copy of an object or an array. However, it has limitations, such as not handling functions, undefined, or circular references.
const originalObject = { a: 1, b: { c: 2 } };const deepCopyObject = JSON.parse(JSON.stringify(originalObject));
Using Lodash's _.cloneDeep()
Lodash is a popular utility library that provides a _.cloneDeep() method for deep copying objects and arrays.
const _ = require('lodash');const originalObject = { a: 1, b: { c: 2 } };const deepCopyObject = _.cloneDeep(originalObject);
Other methods
Using recursion
For custom deep copy logic, you can implement a recursive function.
function deepCopy(obj) {if (obj === null || typeof obj !== 'object') {return obj;}if (Array.isArray(obj)) {return obj.map((item) => deepCopy(item));}const copy = {};for (const key in obj) {if (obj.hasOwnProperty(key)) {copy[key] = deepCopy(obj[key]);}}return copy;}const originalObject = { a: 1, b: { c: 2 } };const deepCopyObject = deepCopy(originalObject);