text: exports.getRandomCode = function(len, charSet) {
  
      charSet = charSet || 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyzabcdefghijkl6789';
  
      var randomString = '';
  
      for (var i = 0; i < len; i++) {
          var randomPoz = Math.floor(Math.random() * charSet.length);
          randomString += charSet.substring(randomPoz, randomPoz + 1);
      }
      return randomString;
  };