<!DOCTYPE html>
<html>
<body>
<p id="demo">请点击按钮来获得文档首个子节点的节点名。</p>
<button onclick="myFunction()">试一下</button>
<script>
function myFunction()
{
var x=document.getElementById("demo");
x.innerHTML=document.firstChild.nodeName;
}
</script>
</body>
</html>