Simple function to generate a random mask url

uuid.js

var uuid = function () {
    var mask = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx';
    return (function (mask) {
        return mask.replace(/[xy]/g, function (c) {
            var r = Math.random() * 16 | 0, v = c === 'x' ? r : (r & 0x3 | 0x8);
            return v.toString(16);
        });
    }(mask));
}