UUID字符串使用

function uuid(num) {
    var s = [];
    var hexDigits = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
    for (var i = 0; i < num; i++) {
      s[i] = hexDigits.substr(Math.floor(Math.random() * 0x10), 1);
    }
    s[14] = "4";
    s[19] = hexDigits.substr((s[19] & 0x3) | 0x8, 1);
    s[8] = s[13] = s[18] = s[23] = "-";
    var uuid = s.join("");
    return uuid;
}