给个例子给你。
<html>
<head>
<title>List</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<script LANGUAGE="javascript">
<!--
var onecount;
onecount=0;
subcat = new Array();
subcat[0] = new Array("徐汇区","01","001");
subcat[1] = new Array("嘉定区","01","002");
subcat[2] = new Array("黄浦区","01","003");
subcat[3] = new Array("南昌市","02","004");
subcat[4] = new Array("九江市","02","005");
subcat[5] = new Array("上饶市","02","006");onecount=6;function changelocation(locationid)
{
document.myform.smalllocation.length = 0; var locationid=locationid;
var i;
document.myform.smalllocation.options[0] = new Option('====所有地区====','');
for (i=0;i < onecount; i++)
{
if (subcat[i][1] == locationid)
{
document.myform.smalllocation.options[document.myform.smalllocation.length] = new Option(subcat[i][0], subcat[i][2]);
}
}
} //-->
</script>
</head>
<body>
<form name="myform" method="post">
<select name="biglocation" onChange="changelocation(document.myform.biglocation.options[document.myform.biglocation.selectedIndex].value)">
<option value="01" selected>上海</option>
<option value="02">江西</option>
</select>
<select name="smalllocation">
<option selected value="">==所有地区==</option>
</select>
</form>
<script LANGUAGE="javascript">
<!--
changelocation(document.myform.biglocation.options[document.myform.biglocation.selectedIndex].value);
//-->
</script>
</body>
</html>
<html>
<head>
<title>List</title>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<script LANGUAGE="javascript">
<!--
var onecount;
onecount=0;
subcat = new Array();
subcat[0] = new Array("徐汇区","01","001");
subcat[1] = new Array("嘉定区","01","002");
subcat[2] = new Array("黄浦区","01","003");
subcat[3] = new Array("南昌市","02","004");
subcat[4] = new Array("九江市","02","005");
subcat[5] = new Array("上饶市","02","006");onecount=6;function changelocation(locationid)
{
document.myform.smalllocation.length = 0; var locationid=locationid;
var i;
document.myform.smalllocation.options[0] = new Option('====所有地区====','');
for (i=0;i < onecount; i++)
{
if (subcat[i][1] == locationid)
{
document.myform.smalllocation.options[document.myform.smalllocation.length] = new Option(subcat[i][0], subcat[i][2]);
}
}
} //-->
</script>
</head>
<body>
<form name="myform" method="post">
<select name="biglocation" onChange="changelocation(document.myform.biglocation.options[document.myform.biglocation.selectedIndex].value)">
<option value="01" selected>上海</option>
<option value="02">江西</option>
</select>
<select name="smalllocation">
<option selected value="">==所有地区==</option>
</select>
</form>
<script LANGUAGE="javascript">
<!--
changelocation(document.myform.biglocation.options[document.myform.biglocation.selectedIndex].value);
//-->
</script>
</body>
</html>
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>无标题文档</title>
</head><script language="javascript">
<!--
function alter(obj){
var b=document.form1.select3;
if(document.form1.select1.value=="2"){
capacity1.innerHTML="222:";
capacity2.innerHTML="<input type=text name=capa>";
b.options[0].text="21";
b.options[1].text="22";
b.options.add(new Option("23","23"));
b.options.add(new Option("24","24"));
b.options.add(new Option("25","25"));
}else{
capacity1.innerHTML="111:";
capacity2.innerHTML="<input type=text name=capa>";
b.options[0].text="11";
b.options[1].text="12";
//因为删除后options的序号变了,所以虽然下面的删除序号相同,但其实质是删除了不同内容
b.options.remove(2);
b.options.remove(2);
b.options.remove(2);
}
}
---></script>
<body>
<form method="post" name="form1" action="">
<table border="1">
<tr class="TdLeftBg">
<td ><div align="center">类型:</div></td>
<td ><select name="select1" onChange="alter();" style="width:150">
<option value="1" >1</option>
<option value="2" >2</option>
</select>
<select name="select3" style="width:150">
<option>11</option>
<option>12</option>
</select></td>
<td id="capacity1" align="center" >111:</td>
<td id="capacity2"><input type="text" name="capa">
</td>
</tr></table>
</form>
</body>
</html>
我觉得这是一种思路!!