code: function addSep(numberString) {
      var parts = numberString.split('.');
      parts[0] = parts[0].replace(/\B(?=(\d{3})+(?!\d))/g, ",");
      return parts.join('.');
    }
docs: Nice regex from  http://stackoverflow.com/questions/2901102/how-to-print-number-with-commas-as-thousands-separators-in-javascript