JavaScript random string of specific length

Hi Guys,
             The below java script code generates a random string of specific length.

function getRandomByLength(randomStrLength) {

       var chars =        "0123456789ABCDEFGHIJKLMNOPQRSTUVWXTZabcdefghiklmnopqrstuvwxyz";
      var randomstring = '';
      for (var i=0; i<randomStrLength; i++) {
      var rnum = Math.floor(Math.random() * chars.length);
      randomstring += chars.substring(rnum,rnum+1);
    }
        return randomstring;
}