Generate UUID in javascript

uuid.js

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