选修课程的级联。

	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
	<html xmlns="http://www.w3.org/1999/xhtml">
	<head>
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
	<title>无标题文档</title>
	</head>

	<body>
	<script language="javascript">

	function changeCity(){
	var cityList =new Array();
	cityList['第一学期']=['html','c#'];
	cityList['第二学期']=['sqlserver','Ado.net','Asp.net','xml'];
	cityList['第二学年']=['刘德华','李宇春','曾轶可'];
	var pIndex=document.form1.select1.value;
	var newOption1;
	document.form1.select2.options.length=0;
	for(var j in cityList[pIndex]){
	newOption1=new Option(cityList[pIndex][j],cityList[pIndex][j]);
	document.form1.select2.options.add(newOption1);
	}
	}
	</script>
	<form id="form1" name="form1" method="post" action="" >
	<table width="234" height="104" border="0" align="center" cellpadding="0" cellspacing="0">
	<tr>
	<td colspan="2"><div align="center">考试申请</div></td>
	</tr>
	<tr>
	<td width="76">学期</td>
	<td width="124"><label>
	<select name="select1" id="select1" onchange="changeCity()">
	<option value="">请选择学期</option>
	<option value="第一学期">第一学期</option>
	<option value="第二学期">第二学期</option>
	<option value="第二学年">第二学年</option>
	</select>
	</label></td>
	</tr>
	<tr>
	<td>课程</td>
	<td><label>
	<select name="select2" id="select2">
	<option>请选择课程</option>
	</select>
	</label></td>
	</tr>
	</table>
	</form>
	</body>
	</html>