code: function rot13(x) {
      return Array.prototype.map.call(x, (ch) => {
          var code = ch.charCodeAt(0);
          if (code >= 0x41 && code <= 0x5a)
              code = (((code - 0x41) + 13) % 26) + 0x41;
          else if (code >= 0x61 && code <= 0x7a)
              code = (((code - 0x61) + 13) % 26) + 0x61;
  
          return String.fromCharCode(code);
      }).join('');
  }
docs: encryption ;)