展开easyui 树节点到某个点

 $(function () {
            $('#tt').tree({
                url: '/IS/Department/JsonTree?companyID=@(Request.QueryString["companyID"])',
                lines: true,
                dnd: true,
                onSelect: function (node) {
                    add(node.id, null);
                    $(this).tree('expand', node.target);  //点击树节点，展开子级节点
                },
                onLoadSuccess: function (node, data) {
                    if (selectID > 0) {
                        var root = $(this).tree("find", selectID);
                        $(this).tree("expandTo", root.target); //展开到某个节点  ，注意这里如果用 $("#tt") 则功能无法实现
                    }
                }, onDrop: function (targetNode, source, point) {
                    debugger;
                    if ("append" == point) {
                        var targetId = $('#tt').tree('getNode', targetNode).id;

                        $.ajax({
                            url: "/IS/Department/UpdateParent",
                            data: { targetId: targetId, sourceid: source.id },
                            success: function () {

                            }
                        })
                    }
                }

            });

            $('#ParentDepartment').combotree('setValue', '@Model.ParentDepartmentID');
        });