Question

select option 如何让第二个下拉栏随着第一个下拉栏选择的内容的变化而变化

代码如下
<form id="form1" name="form1" method="post" action="">
<p>
<select class="amd" onchange="zhuan(i)">

<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
<option value="5">5</option>
</select>
</p>
<p>
<select id="gui" class="amd">
<option>请选择</option>
</select>
</form>
<script type="text/javascript" language="javascript">
function zhuan(obj)
{
if (obj.value == 2)
{
document.getElementById('gui').selected = "<option>1</option><option>2</option>";
}
}

</script>

Answer 1

function createCity(){
//获取选中的索引
var pro=document.getElementById('pro').selectedIndex;
var citys=document.getElementById('city');
citys.options.length=0;//当省发生变化时清空城市列表
var city_len=city[pro].length;
for(var i=0;i<city_len;i++){
var op=new Option(city[pro][i],city[pro][i]);
citys.options.add(op);
}

}