JavaScript实现Select二级联动下拉菜单详解

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<HTML>
 <HEAD>
 <TITLE> New Document </TITLE>
 <META NAME="Generator" CONTENT="EditPlus">
 <META NAME="Author" CONTENT="">
 <META NAME="Keywords" CONTENT="">
 <META NAME="Description" CONTENT="">
 <script language="JavaScript" type="text/javascript">
 //定义了城市的二维数组，里面的顺序跟省份的顺序是相同的。通过selectedIndex获得省份的下标值来得到相应的城市数组
 var city=[
 ["北京","天津","上海","重庆"],
 ["南京","苏州","南通","常州"],
 ["福州","福安","龙岩","南平"],
 ["广州","潮阳","潮州","澄海"],
 ["兰州","白银","定西","敦煌"]
 ];

 function getCity(){
  //获得省份下拉框的对象
  var sltProvince=document.form1.province;
  //获得城市下拉框的对象
  var sltCity=document.form1.city;  
  //得到对应省份的城市数组
  var provinceCity=city[sltProvince.selectedIndex - 1];
 
  //清空城市下拉框，仅留提示选项
  sltCity.length=1;
 
  //将城市数组中的值填充到城市下拉框中
  for(var i=0;i<provinceCity.length;i++){
  sltCity[i+1]=new Option(provinceCity[i],provinceCity[i]);
  }
 }
 </script>
 </HEAD>
 
 <BODY>
 <FORM METHOD=POST ACTION="" name="form1">
  <SELECT NAME="province" onChange="getCity()">
  <OPTION VALUE="0">请选择所在省份 </OPTION>
  <OPTION VALUE="直辖市">直辖市 </OPTION>
  <OPTION VALUE="江苏省">江苏省 </OPTION>
  <OPTION VALUE="福建省">福建省 </OPTION>
  <OPTION VALUE="广东省">广东省 </OPTION>
  <OPTION VALUE="甘肃省">甘肃省 </OPTION>
  </SELECT>
  <SELECT NAME="city">
  <OPTION VALUE="0">请选择所在城市 </OPTION>
  </SELECT>
 </FORM>
 </BODY>
</HTML>

sltCity[i+1]=new Option(provinceCity[i],provinceCity[i]);

 var l=myselect.length;
 for(var i=0;i<l;i++){
 myselect.options[i]=null;
 }

myselect.length=0;