function uuidv4() {
var s = [];
var hexDigits = "0123456789abcdef";
for (var i = 0; i < 36; i++) {
s[i] = hexDigits.substr(Math.floor(Math.random() * 16), 1);
}
s[14] = "4";
s[19] = hexDigits.substr(s[19] & 3 | 8, 1);
s[8] = s[13] = s[18] = s[23] = "-";
var uuid = s.join("");
return uuid;
}