Array.unshift()

The Array.unshift() method in JavaScript adds one or more elements to the beginning of an array and returns the new length of the array. It modifies the original array.

Syntax

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unshift()
unshift(element1)
unshift(element1, element2)
unshift(element1, element2, /* …, */ elementN)

Parameters

ParameterDescription
element1, element2, ..., elementNThe elements to add to the beginning of the array.

Return Value

The unshift() method returns the new length of the array after the specified elements are added to the beginning.

Examples

1. Adding a Single Element

This example demonstrates how to add a single element to the beginning of an array.

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const numbers = [2, 3, 4];

const newLength = numbers.unshift(1);
console.log(numbers);
console.log(newLength);

Output

[1, 2, 3, 4]
4
  1. numbers.unshift(1) adds 1 to the beginning of the numbers array.
  2. The return value is the new length of the array, which is 4.

2. Adding Multiple Elements

You can add multiple elements to the beginning of an array in a single call.

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const fruits = ["banana", "cherry"];

const newLength = fruits.unshift("apple", "orange");
console.log(fruits);
console.log(newLength);

Output

["apple", "orange", "banana", "cherry"]
4
  1. fruits.unshift("apple", "orange") adds "apple" and "orange" to the beginning of the fruits array.
  2. The new length of the array is 4.

3. Using unshift() on an Empty Array

The unshift() method can be used to add elements to an empty array.

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const emptyArray = [];

const newLength = emptyArray.unshift(5, 10);
console.log(emptyArray);
console.log(newLength);

Output

[5, 10]
2

The array emptyArray now contains the elements [5, 10], and its length is 2.

4. Modifying the Original Array

The unshift() method directly modifies the original array.

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const letters = ["b", "c"];

letters.unshift("a");
console.log(letters);

Output

["a", "b", "c"]

The unshift() method modifies the letters array by adding "a" at the beginning.