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] = "-";

    var uuid = s.join("");

    return uuid;

}

function guid() {

    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {

        var r = Math.random()*16|0, v = c == 'x' ? r : (r&0x3|0x8);

        return v.toString(16);

    });

}

function guid() {

    function S4() {

       return (((1+Math.random())*0x10000)|0).toString(16).substring(1);

    }

    return (S4()+S4()+"-"+S4()+"-"+S4()+"-"+S4()+"-"+S4()+S4()+S4());

}

function uuid(len, radix) {

    var chars = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'.split('');

    var uuid = [], i;

    radix = radix || chars.length;

    if (len) {

      // Compact form

      for (i = 0; i < len; i++) uuid[i] = chars[0 | Math.random()*radix];

    } else {

      // rfc4122, version 4 form

      var r;

      // rfc4122 requires these characters

      uuid[8] = uuid[13] = uuid[18] = uuid[23] = '-';

      uuid[14] = '4';

      // Fill in random data.  At i==19 set the high bits of clock sequence as

      // per rfc4122, sec. 4.1.5

      for (i = 0; i < 36; i++) {

        if (!uuid[i]) {

          r = 0 | Math.random()*16;

          uuid[i] = chars[(i == 19) ? (r & 0x3) | 0x8 : r];

        }

      }

    }

    return uuid.join('');

}

// 8 character ID (base=2)

uuid(8, 2)  //  "01001010"

// 8 character ID (base=10)

uuid(8, 10) // "47473046"

// 8 character ID (base=16)

uuid(8, 16) // "098F4D35"