easyui related problems

//某一节点下的所有子节点
function getChildren(id/*节点ID*/){
    var $tree = $('#tree');
    var node = $tree.tree('find',id);
    var childrenNodes = $tree.tree('getChildren',node.target);
    return childrenNodes;
}
//某节点的一级节点
function getSubChildren(id){
    var $tree = $('#tree');
    var node = $tree.tree('find',id);
    var subNodes = [];
    $(node.target)
    .next().children().children("div.tree-node").each(function(){   
        subNodes.push($tree.tree('getNode',this));
    });
   return subNodes;
}