//定义了车型的二维数组，里面的顺序跟品牌的顺序是相同的。通过selectedIndex获得品牌的下标值来得到相应的车型数组     
      var city=[
     ["骊威","天籁","奇骏","逍客","骐达","轩逸","颐达"],
     ["C5","世嘉","凯旋","C2","毕加索","新爱丽舍"],
     ["CRV","思域","思铂睿"],
	 ["海马福仕达"],
     ];

     function getCity(){
         //获得品牌下拉框的对象
         var sltProvince=document.forms[0].province;
         //获得车型下拉框的对象
         var sltCity=document.forms[0].city;
         
         //得到对应品牌的车型数组
         var provinceCity=city[sltProvince.selectedIndex - 1];

         //清空车型下拉框，仅留提示选项
         sltCity.length=1;

         //将车型数组中的值填充到车型下拉框中
         for(var i=0;i<provinceCity.length;i++){
             sltCity[i+1]=new Option(provinceCity[i],provinceCity[i]);
         }
     }