JavaScript Array Manipulation Methods

JavaScript provides several methods to copy, merge, remove, and insert array elements. These methods are commonly used when working with arrays in JavaScript.

In this article, you will learn:

• concat()
• slice()
• splice()
• delete operator

Array concat()

The concat() method joins two or more arrays and returns a new array.

It does not modify the original arrays.

Syntax

array1.concat(array2, array3, …)

Parameters

• array2, array3… → Arrays or values to join.

Return Value: Returns a new merged array.

Example

let frontend = ["HTML", "CSS"];
let backend = ["JavaScript", "Node.js"];
let courses = frontend.concat(backend);
console.log(courses);

Output

[“HTML”, “CSS”, “JavaScript”, “Node.js”]

Array slice()

The slice() method returns a selected portion of an array.

It does not modify the original array.

Syntax

arrayName.slice(start, end)

Parameters

• start → Starting index (included).
• end → Ending index (excluded). Optional.

Return Value: Returns a new array.

Example

let fruits = ["Apple", "Banana", "Mango", "Orange"];
let result = fruits.slice(1, 3);
console.log(result);

Output

[“Banana”, “Mango”]

Array splice()

The splice() method adds, removes, or replaces elements in an array.

It changes the original array.

Syntax

arrayName.splice(start, deleteCount, item1, item2, …)

Parameters

• start → Index where the operation begins.
• deleteCount → Number of elements to remove.
• item1, item2… → Elements to insert (optional).

Return Value: Returns an array containing the removed elements.

Example 1: Remove Elements

let fruits = ["Apple", "Banana", "Mango", "Orange"];
fruits.splice(1, 2);
console.log(fruits);

Output

[“Apple”, “Orange”]

Example 2: Add Elements

let fruits = ["Apple", "Orange"];
fruits.splice(1, 0, "Banana", "Mango");
console.log(fruits);

Output

[“Apple”, “Banana”, “Mango”, “Orange”]

Array delete Operator

The delete operator removes an element from an array.

However, it does not remove the index. Instead, it leaves an empty slot in the array.

Because of this, using splice() is usually a better choice.

Syntax

delete arrayName[index]

Example

let fruits = ["Apple", "Banana", "Mango"];
delete fruits[1];
console.log(fruits);
console.log(fruits.length);

Output

[“Apple”, empty, “Mango”]

3

Method Comparison