addExtra.js

/*
Add an item to the list:

AddExtra method adds a new item to the list and returns the list. The new item can be any object, and it does not matter. (lets say you add an integer value, like 13)

In our test case we check to assure that the returned list has one more item than the input list. However the method needs some modification to pass this test.
*/

//Answer//

let addExtra = listOfNumbers => [...listOfNumbers,0]