有人帮我看看吗，为什么输出不出来，哪里错了呢

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>作业5-2</title>
</head>
<body>
    <div id="list1">
       第一章
    </div>
    <button onclick="add()">添加章节</button>
    <button onclick="del()">删除章节</button>
    <script>
        var i=1;
        var addch1=document.getElementById("addch1");
        var list1=document.getElementById("list1");
1
        function add(obj){
            var parent=obj.parentNode;
            var s="&nbsp &nbsp第"+i+"节";
            var node=document.createElement("div");
            node.innerHTML=s;
            parent.appendChild(node);
            i++;
            event.stopPropagation();
            node.appendChild(parentNode)
            addch1.appendChild(node)
        }

        function del(obj){
            var parent=obj.parentNode;
            parent.removeChild(parent.childNodes[parent.childNodes.length-1]);
            i--;
        }
    </script>
</body>
</html>

```javascript

```

你这代码不全啊。。。 html少标签。那就没法补全 js.
这是我补全的

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>作业5-2</title>
</head>

<body>
    <div id="addch1">
        <div id="list1">
            第一章
        </div>
        <button onclick="add()">添加章节</button>
        <button onclick="del()">删除章节</button>
    </div>

    <script>
        var i = 1;
        var addch1 = document.getElementById("addch1");
        var list1 = document.getElementById("list1");

        function add() {
            var list = document.getElementById("list1");
            // console.log(obj, "98")
            var parent =list.parentNode;
            var s = "&nbsp &nbsp第" + i + "节";
            var node = document.createElement("div");
            node.innerHTML = s;
            parent.appendChild(node);
            i++;
            event.stopPropagation();
            node.appendChild(parentNode)
            addch1.appendChild(node)
        }
        function del() {
            var list = document.getElementById("list1");
            var parent = list.parentNode;
            parent.removeChild(parent.childNodes[parent.childNodes.length - 1]);
            i--;
        }
    </script>
</body>

</html>

哪里抄的代码，都不抄全，document.getElementById，你这都没有这两个id命名的容器，你取这两个id，add(obj)，你的obj都没有传入参进来，哪来的obj.parentNode。