2个下拉框，选择1级菜单后，2级菜单出现相应的备选项。如果没有选择则不能提交。
先创建html文件
<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<body>
<form>
<select id="province">
<option selected="selected">请选择...</option>
</select>
<select id="city">
<option selected="selected">请选择...</option>
</select>
<button type="submit" id="where_submit" disabled="disabled">提交</button>
</form>
</body>
<script type="text/javascript">
var provinces=['辽宁','北京','上海','吉林','浙江'];
//最新添加的省份放在最前面
var choice=['请选择...']
var zhejiang=['杭州','嘉兴','宁波','绍兴'];
var shanghai=['金山','闸北','普陀','徐汇'];
var jilin=['长春','辽源','吉林','四平'];
var beijing=['海淀','朝阳','东城','西城'];
var liaoning=['沈阳','大连','盘锦','锦州','辽阳','鞍山']
//城市排序由后到前
var citys=new Array;
citys[0]=choice;
citys[1]=zhejiang;
citys[2]=jilin;
citys[3]=shanghai;
citys[4]=beijing;
citys[5]=liaoning;
function add_option(select,option){
var target=document.getElementById(select);
for (var i = option.length - 1; i >= 0; i--) {
var add_option=document.createElement("option");
add_option.text=option[i];
target.add(add_option,null);
target.lastChild.setAttribute("name",option[i]);
}
}
add_option("province",provinces);
document.getElementById("province").addEventListener("change",function(){
var selevted_province=document.getElementById("province");
var selected_city=document.getElementById("city");
for (var i = selevted_province.length - 1; i >= 0; i--) {
selected_city.remove(i);
}
var selected=selevted_province.selectedIndex;
if (selected==0) {
add_option("city",citys[0]);
document.getElementById("where_submit").setAttribute("disabled","ture");
}else{
add_option("city",citys[selected]);
document.getElementById("where_submit").removeAttribute("disabled");
}
})
</script>
</html>
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。