Changing Array Values Using ForEach Loop

Take this array as an example,

const numbers = [1, 2, 3, 4, 5]

and let's add 1 to each element. The forEach method makes this really easy.

numbers.forEach((number, index, array) => {
  array[index] = number + 1
})

console.log(numbers) // Array(5) [ 2, 3, 4, 5, 6 ]

The trick is to use a 3^rd argument in the callback function that gives you access to the array. Be aware that this operation mutates the original array.