How can I clone an array in JavaScript?

JavaScript provides quite a few ways to clone an array, most of which are pretty similar in terms of performance and results. Here's a quick rundown of some of the available options.

The spread operator

ES6 introduced the spread operator (...), which provides probably the easiest and most common way to create a shallow clone of an array.

let x = [1, 2, 3, 4];
let y = [...x];

Array.from()

Array.from() has a very powerful API that can be used for many different things, including creating a copy of an array.

let x = [1, 2, 3, 4];
let y = Array.from(x);

Array.prototype.slice()

Similarly to the spread operator, Array.prototype.slice() can be used to create a shallow copy of an array.

let x = [1, 2, 3, 4];
let y = x.slice();

Array.prototype.map()

Looking into one of the more unorthodox options, Array.prototype.map() can be used to map each element of an array to itself to create a new array.

let x = [1, 2, 3, 4];
let y = x.map(i => i);

Array.prototype.filter()

Similarly, Array.prototype.filter() can be used to return true for each and every element, resulting in a new array with all of the original array's elements.

let x = [1, 2, 3, 4];
let y = x.filter(() => true);

Object.assign()

Finally, Object.assign() can be used in the exact same way as it's used to create a clone of an object, but for an array instead.

let x = [1, 2, 3, 4];
let y = Object.assign([], x);

structuredClone()

If you're looking to clone an array that contains objects, functions or class instances, you can use the structuredClone() global function, which can be used to deep clone objects.

const a = [{ foo: 'bar' }, { baz: 'qux' }];
const b = structuredClone(a); // a !== b, a[0] !== b[0]