de, fn));
    };

    // triggers when user clicks on thumbnail
    var onThumbnailsClick = function(e) {
      e = e || window.event;
      e.preventDefault ? e.preventDefault() : e.returnValue = false;

      var eTarget = e.target || e.srcElement;

      // find root element of slide
      var clickedListItem = closest(eTarget, function(el) {
        return (el.tagName &amp;&amp; el.tagName.toUpperCase() === 'FIGURE');
      });

      if (!clickedListItem) {
        return;
      }

      // find index 