function jumpScroll(e) {
      // If the drag handle element was pressed, don't do anything here.
      if (e.target === $dragHandleEl[0]) {
        return;
      }

      // The content will scroll by 7/8 of a page.
      var jumpAmt = pageJumpMultp * $scrollContentEl[sizeAttr]();

      // Calculate where along the scrollbar the user clicked.
      var eventOffset = (scrollDirection === 'vert') ? e.originalEvent.layerY : e.originalEvent.layerX;

      // Get the position of the top (or left) of the drag handle.
      var dragHandleOffset = $dragHandleEl.position()[offsetAttr];

      // Determine which direction to scroll.
      var scrollPos = (eventOffset < dragHandleOffset) ? $scrollContentEl[scrollOffsetAttr]() - jumpAmt : $scrollContentEl[scrollOffsetAttr]() + jumpAmt;

      $scrollContentEl[scrollOffsetAttr](scrollPos);
    }
Scroll in the same manner as the PAGE UP/DOWN keys