JavaScript Array.concat() Method

Array.concat()

The Array.concat() method in JavaScript is used to merge two or more arrays into a new array. This method does not modify the existing arrays but instead returns a new array.

Syntax

concat()
concat(value1)
concat(value1, value2)
concat(value1, value2, /* …, */ valueN)

Parameters

Parameter	Description
value1, value2, ..., valueN	Arrays or values to concatenate with the calling array. These can be arrays, individual elements, or a combination of both.

Return Value

The concat() method returns a new array that includes all elements of the calling array, followed by the elements or values provided as arguments.

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Examples

1. Concatenating Two Arrays

In this example, two arrays are concatenated into a new array.

const array1 = [1, 2, 3];
const array2 = [4, 5, 6];

const result = array1.concat(array2);
console.log(result);

Output

[1, 2, 3, 4, 5, 6]

1. array1.concat(array2) combines the elements of array1 and array2 into a single array.

2. Concatenating Arrays and Values

This example demonstrates how to concatenate arrays and additional values.

const array = [1, 2, 3];

const result = array.concat(4, [5, 6]);
console.log(result);

Output

[1, 2, 3, 4, 5, 6]

1. array.concat(4, [5, 6]) merges the original array, the value 4, and the array [5, 6].

3. Concatenating Nested Arrays

The concat() method does not flatten nested arrays. Nested arrays are added as-is.

const array1 = [1, 2];
const array2 = [[3, 4]];

const result = array1.concat(array2);
console.log(result);

Output

[1, 2, [3, 4]]

The nested array [3, 4] is included as a single element.

4. Using concat() to Clone an Array

The concat() method can be used to create a shallow copy of an array.

const array = [1, 2, 3];

const clonedArray = array.concat();
console.log(clonedArray);

Output

[1, 2, 3]

Here, array.concat() creates a shallow copy of the original array.