JS: How to subtract 1 (2, 3…) from each number in the array

I need this function pretty often that’s why I just leave it here.

Suppose we have an array:

var array = [1, 2, 3, 4, 5];

In the result we need something like that:

var array2 = [0, 1, 2, 3, 4];

How to subtract 1 from each number in the array

There are two simple ways to do that.

Using map method

You can use .map ().

The solution will be:

var array2 = array.map( function(value) {
return value - 1;
} );

Using for-loop method

Code for the second one is longer but it is here for the demonstration.

// Create an array to hold our new values
var array2 = [];

// Iterate through each element in the original array
for(var i = 0; i < array.length; i++) { // Decrement the value of the original array and push it to the new one array2.push(array[i] - 1); }

"- 1" can be changed to any other math operation like "+ 2", "*6", "/1.2", etc.