javascript - insertbefore issue with replacing parent element
Code before modification
<!DOCTYPE HTML>
<html lang="en-US">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<button id='btn'>创建元素</button>
<script type="text/javascript">
var btn = document.getElementById('btn');
//注册点击事件
btn.onclick = function(){
//创建一个元素
var h1 = document.createElement('h1');
h1.innerHTML = "这是新增h1标签";
console.log( h1 );
//使用appendChild的方式
//document.body.appendChild( h1 );
//使用insertBefore的方式
//是在父元素中，先找一个节点，然后插入到它之前
document.body.insertBefore(h1,btn); //新插入的节点是h1，作为第一个参数
}
</script>
</body>
</html>Modified code
<!DOCTYPE HTML>
<html lang="en-US">
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<p id="box">
<button id='btn'>创建元素</button>
</p>
<script type="text/javascript">
var btn = document.getElementById('btn');
//注册点击事件
btn.onclick = function(){
//创建一个元素
var h1 = document.createElement('h1');
var box = document.createElement('box');
h1.innerHTML = "这是新增h1标签";
console.log( h1 );
//使用appendChild的方式
//document.body.appendChild( h1 );
//使用insertBefore的方式
//是在父元素中，先找一个节点，然后插入到它之前
document.box.insertBefore(h1,btn); //新插入的节点是h1，作为第一个参数
}
</script>
</body>
</html>After modification, elements cannot be added. What is the problem. The previous addition had body as the parent element and was used directly without passing it. I have nested a p and obtained the elements in advance. But still cannot insert new elements
