// .push takes one or more parameters and pushes them onto the end of the array.
var arr = [1,2,3];
arr.push(4);
//arr is now [1,2,3,4]
// .pop() is used to pop an value of the end of an array
var arr = [1,2,3];
arr.pop();
//arr is now [1,2]
// .shift is used to remove the first item from an array
var arr = [1,2,3];
arr.shift();
//arr is now [2,3]
// .unshift() adds an item at the beginning of the array
var arr = [1,2,3];
arr.unshift(0);
//arr is now [0,1,2,3]