<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<img id="light" src="img/off.gif">
<h1 id="title">aaaa</h1>
<script language="javascript">
alert("添加成功!")
var l=document.getElementById("light");
alert(l);
l.src="img/on.gif";
var title=document.getElementById("title");
alert("change");
title.innerHTML="bbbbb"
</script>
</body>
</html>
无论script放在哪里都是先执行alter语句;按照正常的话不应该是先显示图片再弹alter语句里面的内容吗