JavaScript Array unshift() Method

The Array.unshift() method is a built-in JavaScript function that adds one or more elements to the beginning of an array and returns the new length of the array. This method is useful when you need to prepend elements to an array.

Syntax

arr.unshift(element1, element2, ..., elementN);

Parameters

Parameter	Description
element1, …, elementN	(Required) The elements to be added to the beginning of the array.

Return Value

The method returns the new length of the array after the elements have been added.

Example 1: Adding a Single Element

let arr = [20, 30, 40, 50];
arr.unshift(10);
console.log(arr);  // Output: [ 10, 20, 30, 40, 50 ]
console.log(arr.length);  // Output: 5

Example 2: Adding Multiple Elements

let arr = [30, 40, 50];
let newLength = arr.unshift(10, 20);
console.log(arr);     // Output: [ 10, 20, 30, 40, 50 ]
console.log(newLength);   // Output: 5

Example 3: Using unshift() with an Empty Array

let arr = [];
let newLength = arr.unshift(10);
console.log(arr);  // Output: [ 10 ]
console.log(newLength);   // Output: 1

Example 5: Adding Objects to an Array

let users = [{ name: 'John' }];
users.unshift({ name: 'Alice' });
console.log(users);
// Output: [{ name: 'Alice' }, { name: 'John' }]

Supported Browsers

Browser	Support
Chrome	1+
Firefox	1+
Safari	1+
Edge	12+
Opera	4+
Internet Explorer	5.5+