// more stuff
/*
where:
'self.elements' is the li selector
'items_in_screen' is the total elements in the screen
see the comment to watch the result GIF
*/
  var self = this;
  var l = self.elements.length
  // self.sel
  if(l>items_in_screen)
  {
      var start = self.sel - 2;
      var end = self.sel + 2;

      while(start<0)
      {
          start++;
          end++;
      }
      while(end>l)
      {
          start--;
          end--;
      }

      for(var i=0; i<l; i++)
      {
          if(i>=start && i<=end)
              self.elements[i].style.display = '';
          else
              self.elements[i].style.display = 'none';
      }
  }
}
// more stuff