直接上代码吧，想了有半天，看来学的算法忘得差不多了：

dfs

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<!doctype html>
<html>
    <head>
        <meta charset="utf-8">
    </head>
    <body>
       <p>
           hello world1
            <span>
                p1
                <span>p11</span>
            </span>   
        </p>
       <p>hello world2</p>       
        <script>
            function bianli(){
                var html = document.documentElement;
                function dfs(node){
                    // if(node == null)                    //回退到没有节点
                        // return;
                    if(node.nodeType!=1){                  //去掉非元素节点，比如属性节点text
                        dfs(node.parentNode);
                        return;
                    }
                    if(!!node.getAttribute('visited')){    //获取在元素子元素同级的没被访问过的元素，接着访问左子树     
                        var hasChildNotVisited = false;
                        Array.prototype.forEach.call(node.childNodes, function(node, index){        
                            if(node.nodeType==1 && !node.getAttribute('visited')){
                                hasChildNotVisited = true;
                                dfs(node);
                            }
                        });
                        if(!hasChildNotVisited){
                            dfs(node.parentNode);
                        }
                    }
                    node.setAttribute('visited', 'true');
                    console.log(node.nodeName);
                    var fc = node.firstChild;
                    if(!!fc)
                        dfs(fc);
                    else
                        dfs(node);
                }
                dfs(html);
            }
            bianli();
        </script>
    </body>
</html>

bfs

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<!doctype html>
<html>
    <head>
        <meta charset="utf-8">
    </head>
    <body>
        <div>
            <div>
                <p>
                    <span></span>
                </p>
            </div>
        </div>
        <script>
            function bianli(){
                var html = document.documentElement;
                var temp = [html];
                function bfs(index){
                    if(!temp[index])
                        return;
                    console.log(temp[index].nodeName);
                    Array.prototype.forEach.call(temp[index].childNodes, function(node, i){
                        if(node.nodeType==1){
                            temp.push(node);
                        }
                    });
                    bfs(++index)
                }
                bfs(0);
            }
            bianli();
        </script>
    </body>
</html>

做个记录