Using Arrays in Javascript retain their values by references.

var oneArray = ["a", "b", "c"];
var anotherArray = oneArray;
anotherArray[0] = "z";

console.log(oneArray, anotherArray);
// ["z", "b", "c"], ["z", "b", "c"]

Ok, but let’s say you’ll need to make a copy of the array. How do you do that?

var oneArray = ["a", "b", "c"];
var anotherArray = oneArray.slice(0);
anotherArray[0] = "z";

console.log(oneArray, anotherArray);
// ["a", "b", "c"], ["z", "b", "c"]

If you’d really, really want you could also wrap it into a prototype function. Although the code-characters savings are minimal.

Array.prototype.copy = function() {
	return this.slice(0);
}

var anotherArray = oneArray.slice(0);
//vs
var anotherArray = oneArray.copy();

Minimal, but maybe contextually for self-explaining.