function uuid() {
    var d = new Date().getTime();
    if (typeof performance !== 'undefined' && typeof performance.now === 'function'){
        d += performance.now(); //use high-precision timer if available
    }
    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function (c) {
        var r = (d + Math.random() * 16) % 16 | 0;
        d = Math.floor(d / 16);
        return (c === 'x' ? r : (r & 0x3 | 0x8)).toString(16);
    });
}

Based on Stackoverflow topic: https://stackoverflow.com/questions/105034/create-guid-uuid-in-javascript

Here’s a similar RFC4122 version 4 compliant solution that solves that issue by offsetting the first 13 hex numbers by a hex portion of the timestamp. That way, even if Math.random is on the same seed, both clients would have to generate the UUID at the exact same millisecond (or 10,000+ years later) to get the same UUID  – Briguy37

Test: https://jsfiddle.net/xg7tek9j/460/