<!DOCTYPE html> <html> <head> <title>我的标题</title> </head> <body> <h1>Document 对象</h1> <h2>head 属性</h2> <p>head 元素的第一个子元素的标签名是:</p> <p id="demo"></p> <script> let tag =document.getElementsByTagName("head")[0].tagName; document.getElementById("demo").innerHTML = tag; </script> </body> </html>