code: 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);
      }
docs: Scroll in the same manner as the PAGE UP/DOWN keys