sample of selecting 5 random items from an array in javascript without any duplications

example.js

a = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","aa","bb","cc","dd"];
b = [];
while(b.length<5){
	t = Math.round(Math.random() * (a.length-1));
	console.log(t,$.inArray(a[t],b));
	if($.inArray(a[t],b) == -1){
		b.push(a[t]);
	}
}
console.log(b[0]);