How do I subtract 1 from each number in an array? [duplicate]

Question

If I have

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

How would i make it into

var numberarr2 = [0, 1, 2, 3, 4];

by decrementing 1 from each element?

Answer 1

You can use .map( )

var numberarr2 = numberarr.map( function(value) { 
    return value - 1; 
} );

Answer 2

Try this:

// Create an array to hold our new values
var numberArr2 = [];

// Iterate through each element in the original array
for(var i = 0; i < numberArr1.length; i++) {

    // Decrement the value of the original array and push it to the new one
    numberArr2.push(numberArr1[i] - 1);
}