Replace an Item in a JavaScript Array

JavaScript provides several ways to replace an item in an array, depending on whether the index or value is known.

• Direct indexing is best when the position is known.
• splice() can replace an item at a specific index.
• indexOf() can find an item before replacing it.

Approach 1: Using Array Indexing

Array indexing allows you to directly replace an item by assigning a new value to its index. This modifies the original array.

let arr = [1, 2, 3, 4, 5];

const idx = 2;
const val = 10;

arr[idx] = val;

console.log(arr);

[ 1, 2, 10, 4, 5 ]

Approach 2: Using splice() Method

The splice() method can replace one or more elements at a specific index.

let arr = [10, 20, 30];

arr.splice(1, 1, 25);

console.log(arr);

[ 10, 25, 30 ]

Approach 3: Using indexOf() Method

The indexOf() method can find the position of a specific value, which can then be replaced using array indexing.

const arr = ['a', 'b', 'c'];
const idx = arr.indexOf('a');
if (idx !== -1) {
    arr[idx] = 'z';
}
console.log(arr);