Array Unshift in JavaScript
Mar 4, 2022
The unshift() function adds one or more elements to the beginning of the array and returns the new length of the array.
const array = [3, 4, 5];
array.unshift(1, 2); // 5
array; // 1, 2, 3, 4, 5Unshifting an Array
If you want to unshift an array, unshift([1, 2]) will add [1, 2] as the first element of the array.
unshift() does not flatten arrays.
const array = [3, 4, 5];
array.unshift([1, 2]); // 4
array; // [[1,2], 3, 4, 5]If you want to unshift the elements of an array, you should use the spread operator as shown below.
const array = [3, 4, 5];
const array2 = [1, 2];
array.unshift(...array2); // 5
array; // 1, 2, 3, 4, 5
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