function showRequest() {
  //alert('before submit!');   
 }
 function reloadCityArr(data){
  var targetSelect=document.getElementById("citySelect");
  clearField(targetSelect)
  for (var i = 0; i < data.length; i++) {   
   var opt = document.createElement("OPTION");
   opt.text=data[i].title;      
   opt.value=data[i].value;  
   targetSelect.add(opt);                            
        }
 }
 
 function clearField(targetSelect){
  
   var listlength=targetSelect.length;
   for (i=listlength-1;i>=0;i--)
         {targetSelect.remove(i);}
 }
//1.prototype方式
 function addChangeProvince(provinceId) {
     var url="__URL__/getCityMap/provinceId/"+provinceId;
    
     new Ajax.Request(url,{
        method: 'get', 
        onComplete: function(transport){ 
        reloadCityArr(eval(transport.responseText));        
     }});
 }
//2.jquery
function addChangeProvince(provinceId) {
     var url="__URL__/getCityMap/provinceId/"+provinceId;    
     $.ajax({
         type: "POST",
         url: url,
         data: "name=John&location=Boston",
         dataType:"json",
         success: function(data){
           reloadCityArr(data);   
          
        
        }
     });
 }
//3.thinkajax
 function complete(data,status,info){
  if (status==1){
   reloadCityArr(data);
  }
 }
 function addChangeProvince(provinceId) {
     var url="__URL__/getCityMap/provinceId/"+provinceId;
     ThinkAjax.sendForm('form1',url,complete,'result');
 }