How does the unshift() method change the following array? code example

Example 1: javascript add new array element to start of array

var colors = ["white","blue"];
colors.unshift("red"); //add red to beginning of colors
// colors = ["red","white","blue"]

Example 2: prepend to js array

var a = [1, 2, 3, 4];
a.unshift(0);
a; // => [0, 1, 2, 3, 4]