Shift, unshift, push, pop in javascript

gistfile1.txt

var arr = [1,2,3,4,5,6,7];

var first = arr.shift(); // first = 1, arr = [2,3,4,5,6,7]
arr.unshift(0); // arr = [0,2,3,4,5,6,7]

arr.push(8); // arr = [0,2,3,4,5,6,7,8]
var last = arr.pop() // last = 8, arr = [0,2,3,4,5,6,7]