为什么不输出JavaScript里的内容？
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>无标题文档</title>
</head>
<body>
<p id="intro">我的课程</p>
<ul>
<li title="JS">JavaScript</li>
<li title="JQ">JQuery</li>
<li title="">HTML/CSS</li>
<li title="JAVA">JAVA</li>
<li title="">PHP</li>
</ul>
<h1>以下为li列表title的值,当title为空时，新设置值为"WEB前端技术："</h1>
<script type="text/javascript">
var Lists=document.getElementsByTagName("li");
for (var i=0; i<Lists.length;i++)
{
var text = lists[i].getAttribute("title");
document.write(text +"<br>");
if(text=="")
{
lists[i].setAttribute("title","web前端技术");
document.write(Lists[i].getAttribute("title")+"<br>");
}
}
</script>
</body>
</html>
