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"