text: function(){
      var el = arguments[0];
      var top = el.offsetTop;
      var left = el.offsetLeft;
      var width = el.offsetWidth;
      var height = el.offsetHeight;
  
      while (el.offsetParent) {
          el = el.offsetParent;
          top += el.offsetTop;
          left += el.offsetLeft;
      }
  
      return (
          top < (window.pageYOffset + window.innerHeight) &&
          left < (window.pageXOffset + window.innerWidth) &&
          (top + height) > window.pageYOffset &&
          (left + width) > window.pageXOffset
      );
  }