1.this._root 括号中引入这个是什么意思

2.

tree.traverseDF(function(node){
            console.log(node.data)
        });
传入node，搞不懂，这一段都没明白啥意思

3.上源码

        function Node(data) {
            this.data = data;
            this.parent = null;
            this.children= [];
        }

        function Tree(data){
            var node = new Node(data);
            this._root = node;
        }

        // var tree = new Tree('ceo');
        // tree._root;

        //使用DFS方式便利树
        Tree.prototype.traverseDF = function(callback){

            //递归方式便利
            (function recurse(currentNode){
                for(var i = 0, length = currentNode.children.length; i < length; i++){
                    recurse(currentNode.children[i])
                }

                callback(currentNode)
            })(this._root)
        };

        var tree = new Tree('one');

        tree._root.children.push(new Node('two'));
        tree._root.children[0].parent = tree;

        tree._root.children.push(new Node('three'));
        tree._root.children[1].parent = tree;
 
        tree._root.children.push(new Node('four'));
        tree._root.children[2].parent = tree;

        tree.traverseDF(function(node){
            console.log(node.data)
        });

        console.log(tree.traverseDF(node))

看的文章原文地址：https://code.tutsplus.com/zh-...

小弟刚刚入门，希望大神给予指点一二，感激不尽