`Array.prototype.unshift()`

Adds one or more elements to the beginning of an array and returns the new length.

Syntax

arr.unshift(...elements)

Name	Type	Required	Description
`elements`	`any`	No	One or more elements to prepend to the start of the array.

number — The new length of the array.

const a = [3, 4];
const len = a.unshift(1, 2);
console.log(a, len);

Output

[ 1, 2, 3, 4 ] 4

const a = [2];
a.unshift(1);
console.log(a);

Output

[ 1, 2 ]

Mutates the array in place and re-indexes all existing elements (O(n)). Multiple elements are inserted as a group in the given order.