function uuid() {
var dt = new Date().getTime();
var 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;
}