# Changing an array in a loop in JavaScript

Array elements can be changed in a loop. To do this, you need to iterate through the arrays with the usual loop `for`. For example, let's multiply array elements by `2`:

`let arr = [1, 2, 3, 4, 5]; for (let i = 0; i < arr.length; i++) { arr[i] = arr[i] * 2; } console.log(arr); // shows [2, 4, 6, 8, 10]`

Now let's increase each element of the array by one:

`let arr = [1, 2, 3, 4, 5]; for (let i = 0; i < arr.length; i++) { arr[i]++; } console.log(arr); // shows [2, 3, 4, 5, 6]`

And now we increase each element of the array by `5`:

`let arr = [1, 2, 3, 4, 5]; for (let i = 0; i < arr.length; i++) { arr[i] += 5; } console.log(arr); // shows [6, 7, 8, 9, 10]`

Given an array of numbers. Loop through this array and square each element of this array.

Given an array of numbers. Loop through this array and subtract one from each element.

Given an array of numbers. Loop through this array and add `10` to each element.

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