<!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>无标题文档</title> </head> <body> <div id="con"><p>javascript</p><div>jQuery</div><h5>PHP</h5></div> <script type="text/javascript"> var x=document.getElementById("con"); document.write(x.firstChild); document.write(x.lastChild); </script> </body> </html>
因为id为con的那部分子节点是p,div,h5这三个子节点,php可以看成是h5标签的子节点