If you have an array, and you want to randomly shuffle its elements, you can use the Fisher–Yates shuffle algorithm. In JavaScript, it looks like this:
function shuffle(xs) {
var i = xs.length, x, rnd;
while(i) {
rnd = Math.floor(Math.random() * i);
i -= 1;
x = xs[i];
xs[i] = xs[rnd];
xs[rnd] = x;
}
}