关于下拉框的问题,望高人指点

因为初学jsp,对很多东西都不太了解.
现在自己在做个小东西,要用到下拉框的联动,二级的就够了...
我知道思路有两种,一种是选择首级下拉框后,服务器端给以响应,提供第二级的下拉菜单;
另一思路则是在页面加载的时候就在服务器端处理好数据,然后在客户端用js根据首级下拉框的值进行控制二级下拉框.
但现在不知道怎么实现,也不知道哪种思路正确,望各位朋友给我指点迷津...

解决方案 »

  1.   

    哪种思路都正确。。第一种需要借助ajax实现，数据量较大的时，效果比较明显。  第二种只适用于数据量较小的情况，可以将菜单项都出来，根据页面定义的js自动选择二级菜单。
      

  2.   

    那js应该怎么用呢?
    首级下拉框中定义一个onchange="changeNext(this)"  ?
    但是感觉那个函数写起来好麻烦,写不出...
      

  3.   

    这是js 二级联动省级城市下拉框
    参考：<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 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 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","香港","澳门"],
         ["石家庄","唐山","秦皇岛","邯郸","邢台","保定","张家口","承德","沧州","廊坊","衡水"],
         ["太原","大同","阳泉","长治","晋城","朔州","晋中","运城","忻州","临汾","吕梁"],
         ["呼和浩特","包头","乌海","赤峰","通辽","鄂尔多斯","呼伦贝尔","巴彦淖尔","乌兰察布","兴安","锡林郭勒","阿拉善"],
         ["沈阳","大连","鞍山","抚顺","本溪","丹东","锦州","营口","阜新","辽阳","盘锦","铁岭","朝阳","葫芦岛"],
         ["长春","吉林","四平","辽源","通化","白山","松原","白城","延边"],
         ["哈尔滨","齐齐哈尔","鸡西","鹤岗","双鸭山","大庆","伊春","佳木斯","七台河","牡丹江","黑河","绥化","大兴安岭"],
         ["南京","苏州","扬州","无锡","徐州","常州","南通","连云港","淮安","盐城","镇江","泰州","宿迁"],
         ["杭州","宁波","温州","嘉兴","湖州","绍兴","金华","衢州","舟山","台州","丽水"],
         ["合肥","芜湖","蚌埠","淮南","马鞍山","淮北","铜陵","安庆","黄山","滁州","阜阳","宿州","巢湖","六安","亳州","池州","宣城"],
         ["福州","宁德","南平","厦门","莆田","三明","泉州","漳州"],
         ["南昌","上饶","萍乡","九江","景德镇","新余","鹰潭","赣州","吉安","宜春","抚州"],
         ["济南","青岛","淄博","枣庄","东营","烟台","潍坊","威海","济宁","泰安","日照","莱芜","临沂","德州","聊城","滨州","菏泽"],
         ["郑州","开封","洛阳","平顶山","焦作","鹤壁","新乡","安阳","濮阳","漯河","许昌","三门峡","南阳","商丘","信阳","周口","驻马店"],
         ["武汉","十堰","襄樊","鄂州","黄石","荆州","宜昌","荆门","孝感","黄冈","咸宁","随州","恩施"],
         ["长沙","株洲","湘潭","岳阳","邵阳","常德","衡阳","张家界","益阳","郴州","永州","怀化","娄底","湘西"],
         ["广州","清远","潮州","东莞","珠海","深圳","汕头","韶关","佛山","江门","湛江","茂名","肇庆","惠州","梅州","汕尾","阳江","河源","中山","揭阳","云浮"],
         ["南宁","柳州","桂林","梧州","北海","防城港","钦州","贵港","玉林","百色","贺州","河池","来宾","崇左"],
         ["海口","三亚"],
         ["成都","自贡","攀枝花","泸州","德阳","绵阳","广元","遂宁","内江","乐山","南充","宜宾","广安","达州","眉山","雅安","巴中","资阳","阿坝","甘孜","凉山"],
         ["贵阳","六盘水","遵义","安顺","铜仁","毕节","黔西南","黔东南","黔南"],
         ["昆明","曲靖","玉溪","保山","昭通","丽江","普洱","临沧","文山","红河","西双版纳","楚雄","大理","德宏","怒江","迪庆"],
         ["拉萨","昌都","山南","日喀则","那曲","阿里","林芝"],
         ["西安","铜川","宝鸡","咸阳","渭南","延安","汉中","榆林","安康","商洛"],
         ["兰州","白银","定西","敦煌","嘉峪关","金昌","天水","武威","张掖","平凉","酒泉","庆阳","临夏","陇南","甘南"],
         ["西宁","海东","海北","黄南","海南","果洛","玉树","海西"],
         ["银川","石嘴山","吴忠","固原","中卫"],
         ["乌鲁木齐","克拉玛依","吐鲁番","哈密","和田","阿克苏","喀什","克孜勒苏柯尔克孜","巴音郭楞蒙古","昌吉","博尔塔拉蒙古","伊犁哈萨克","阿勒泰"],
         ["台北","高雄","基隆","台中","台南","新竹","嘉义"]
         ];     function getCity(){
             //获得省份下拉框的对象
             var sltProvince=document.forms[0].province;
             //获得城市下拉框的对象
             var sltCity=document.forms[0].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 name="f1">
    <table>
       <tr><td>请选择企业所在城市<font color="red">*</font></td>
        <td><select name="province" onChange="getCity()">
           <option value="null" selected="selected">请选择所在省份</option>
            <option value="直辖市">直辖市</option>
            <option value="河北">河北</option>
            <option value="山西">山西</option>
              <option value="内蒙古">内蒙古</option>
                <option value="辽宁">辽宁</option>
              <option value="吉林">吉林</option>
              <option value="黑龙江">黑龙江</option>
              <option value="江苏">江苏</option>
              <option value="浙江">浙江</option>
              <option value="安徽">安徽 </option>
            <option value="福建">福建 </option>
              <option value="江西">江西</option>
                <option value="山东">山东</option>
              <option value="河南">河南</option>
              <option value="湖北">湖北</option>
              <option value="湖南">湖南</option>
              <option value="广东">广东</option> 
              <option value="广西">广西</option>
                <option value="海南">海南</option>
              <option value="四川">四川</option>
              <option value="贵州">贵州</option>
              <option value="云南">云南</option>
              <option value="西藏">西藏</option>
              <option value="陕西">陕西 </option>
            <option value="甘肃">甘肃 </option>
              <option value="青海">青海</option>
                <option value="宁夏">宁夏</option>
              <option value="新疆">新疆</option>
              <option value="台湾">台湾</option>   
             </select>
         <select name="city">
              <option selected="selected" value="null">请选择所在城市</option>
              </select></td></tr>
         </table></form>
    </BODY>
    </HTML>
      

  4.   

           function localAdd()
    {
    var newOption;
    document.getElementById("test").options.length=0;
    for(var i = 1;i<=<%=你数据库数据数量%>;i++)
    {
        newOption = new Option(<%=得到的值%>
        document.getElementById("menu1").options.add(newOption);
    }

    }