3 ways to use the JavaScript spread operator with arrays

Clone an array

The spread operator can be used to clone an array into a new array. This trick can come in handy when working with arrays of primitives. However, it only shallow clones the array, meaning nested non-primitive values will not be cloned.

const arr = [1, 2, 3];
const arr2 = [...arr];
// [1, 2, 3]

Merge multiple arrays

Using the spread operator, it’s possible to combine two or more arrays into one. You should think of this trick as cloning two arrays into a new one. Due to that, the shallow cloning limitation mentioned previously applies here, too.

const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];
const combined = [...arr1, ...arr2];
// [1, 2, 3, 4, 5, 6]

Add items to an array

Similarly to previous tricks, it’s possible to spread an array into a new one and add individual elements, too. This can also be combined with merging multiple arrays, if desired.

const arr = [1, 2, 3];
const arr2 = [0, ...arr, 4];
// [0, 1, 2, 3, 4]