Array.prototype.map

Array.prototype.map or Array.map for short is a method on Javascript arrays that allows you to map/convert the array items to something else and does not mutate.

It accepts a function/callback that is run for each iteration with iterations array item, and the return value from that function will become the new item in the new array. Once complete it will return the new array containing the mapped/converted items so that you can store it as a variable.

For example, given an array of numbers, if you wanted to multiply each by 10 then you could call map on your array and pass in a function that accepts an item which will be a number, and then returns a value that uses the multiplication operator on the item to multiply it by 10.

This function would then be run for each item in the array multiplying each by 10, once the whole array has been run the map function will return the new multiplied array ready to be used or stored.