docs: function(node) {
      if (!node) {
        return null;
      }
      var ownerDocument = node.ownerDocument;
      while (node && node !== ownerDocument.body) {
        if (_isNodeScrollable(node, 'overflow') ||
            _isNodeScrollable(node, 'overflowY') ||
            _isNodeScrollable(node, 'overflowX')) {
          return node;
        }
        node = node.parentNode;
      }
      return ownerDocument.defaultView || ownerDocument.parentWindow;
    }