js 生成uuid()

 function uuid() {
        var s = [];
        var hexDigits = "0123456789abcdef";
        for (var i = 0; i < 36; i++) {
          s[i] = hexDigits.substr(Math.floor(Math.random() * 0x10), 1);
        }
        s[14] = "4";  // bits 12-15 of the time_hi_and_version field to 0010
        s[19] = hexDigits.substr((s[19] & 0x3) | 0x8, 1);  // bits 6-7 of the clock_seq_hi_and_reserved to 01
        s[8] = s[13] = s[18] = s[23] = "";    //"" 引号里面可以加任意字符，代表拼接的意思，如果不加就是 纯32位支付

        var uuid = s.join("");
        return uuid;
      }