jquery easyui tree动态加载子节点

1.前端tree绑定时，使用onBeforeExpand事件：当节点展开时触发加载子节点，自动会向服务端发送请求：url为绑定url，参数为当前节点id

this.tree = {
        method: 'GET',
        url: self.urls.queryCatalog,
        queryParams: ko.observable(),
        animate:true,
        lines: true,
        showLoading:true,
        loadFilter: function (d) {
            var list = utils.filterProperties(d, ['KEYFIELDNAME as id', 'PARENTFIELDNAME as pid', 'CATALOG_NAME as text']);
            //将数据转换成tree绑定需要的格式
            var treeData = utils.toTreeDataCollapse(list, "id", "pid", "children");
            return treeData;
        },
        onSelect: function (node) {
            self.Catalog(node.id);
        },
        onBeforeExpand: function (node) {
        }
    };

2.后台定义2个方法：一个加载初始节点，一个加载子节点