EasyUI treegrid设置折叠节点(默认展开一级节点)

    $("#mainGrid").treegrid({
      fit: true,
      toolbar: "#toolbar",
      fitColumns: false,
      width: $(window).width() - 22,
      height: $(window).height() - 110,
      rownumbers: false,
      pagination: false,
      striped: true,
      idField: "id",
      treeField: "name",
      columns: [
        [
          {
            field: "name",
            title: "部门名称",
            halign: "center",
            align: "left",
            width: 350
          },
          {
            field: "createName",
            title: "创建人",
            halign: "center",
            align: "center",
            width: 300
          }
        ]
      ],
      loader: function(param, success, error) {
        ajax.getList(param, success);
      },
      // 在 onLoadSuccess函数中设置,遍历所有根节点调用collapseAll.
      onLoadSuccess: function(row, data) {
        $.each(data, function(i, val) {
          $("#mainGrid").treegrid("collapseAll", data[i].id);
        });
      }
    });