Quick UUID in JS

uuid.js

function uuid() {
    var i, random;
    var uuid = '';
    for (i = 0; i < 32; i++) {
        random = Math.random() * 16 | 0;
        if (i === 8 || i === 12 || i === 16 || i === 20) {
            uuid += '-';
        }

        uuid += (i === 12 ? 4 : (i === 16 ? (random & 3 | 8) : random)).toString(16);
    }
    return uuid;
}