初步实现方法：
<html> <head> <script language="javascript"> function changecity(){ var province = document.form1.selprovince.value; var newoption1,newoption2; switch(province){ case "四川省": newoption1 = new Option("成都市", "chengdu"); newoption2 = new Option("绵阳市", "mianyang"); break; case "湖北省" : newoption1= new Option("武汉市","wuhan"); newoption2= new Option("襄樊市","xiangfan"); break; case "山东省" : newoption1= new Option("青岛市","qingdao"); newoption2= new Option("烟台市","yantai"); break; } document.form1.selcity.options.length=0; document.form1.selcity.options.add(newoption1); document.form1.selcity.options.add(newoption2); } </script> </head> <form action="" method="post"> <select onchange="changecity()"> <option>--请选择开户帐号的省份--</option> <OPTION value="四川省">四川省</OPTION> <OPTION value="山东省">山东省</OPTION> <OPTION value="湖北省">湖北省</OPTION> </select> <select> <option>--请选择开户帐号的城市--</option> </select> </form> </html>
改进实现方法：
<html> <head> <script language="javascript"> function changecity(){ var cityList = new Array(); cityList[0]=['成都', '绵阳', '德阳', '自贡']; cityList[1]=['济南', '青岛', '淄博', '枣庄']; cityList[2]=['武汉', '宜昌', '荆州', '襄樊']; var pindex = document.form1.selprovince.selectedIndex-1; var newoption1; document.form1.selcity.options.length = 0; for(var j in cityList[pindex]){ newoption1 = new Option(cityList[pindex][j], cityList[pindex][j]); document.form1.selcity.options.add(newoption1); } } </script> </head> <form action="" method="post"> <select onchange="changecity()"> <option>--请选择省份--</option> <OPTION value="四川省">四川省</OPTION> <OPTION value="山东省">山东省</OPTION> <OPTION value="湖北省">湖北省</OPTION> </select> <select> <option>--请选择城市--</option> </select> </form> </html>
改进方法2：
<html> <head> <script language="javascript"> function citychange(){ var cityList = new Array(); cityList['辽宁省'] = ['沈阳','鞍山','大连']; cityList['山东省'] = ['济南','烟台','蓬莱']; cityList['山西省'] = ['太原','大同','平遥']; var pindex = document.form1.selprovince.value; var newoption1; document.form1.selcity.options.length = 0; for(var i in cityList[pindex]){ newoption1 = new Option(cityList[pindex][i],cityList[pindex][i]); document.form1.selcity.options.add(newoption1); } } </script> </head> <form action="" method="post"> <select onchange="citychange()"> <option>请选择省份</option> <OPTION value="辽宁省">辽宁省</OPTION> <OPTION value="山东省">山东省</OPTION> <OPTION value="山西省">山西省</OPTION> </select> <select> <option>请选择城市</option> </select> </form> </html>