1function uuid(){
2    var dt = new Date().getTime();
3    var uuid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
4        var r = (dt + Math.random()*16)%16 | 0;
5        dt = Math.floor(dt/16);
6        return (c=='x' ? r :(r&0x3|0x8)).toString(16);
7    });
8    return uuid;
9}
10
11

1function uuidv4() {
2  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
3    var r = Math.random() * 16 | 0, v = c == 'x' ? r : (r & 0x3 | 0x8);
4    return v.toString(16);
5  });
6}
7
8console.log(uuidv4());

1function uuid() {
2  return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
3    var r = Math.random() * 16 | 0, v = c == 'x' ? r : (r & 0x3 | 0x8);
4    return v.toString(16);
5  });
6}
7
8var userID=uuid();//something like: "ec0c22fa-f909-48da-92cb-db17ecdb91c5" 

1function uuidv4() {
2  return ([1e7]+-1e3+-4e3+-8e3+-1e11).replace(/[018]/g, c =>
3    (c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
4  );
5}
6
7console.log(uuidv4());