js中一個函數獲取另一個函數返回值問題

//此種爲異步，還不等ajax賦完值，函數就return了。
  function getCaseInfoForMap(){
   var formInfo=$("#firstForm").serialize();
   var dd;
    $.ajax({
     type:"post",
     url:"<%=path %>/webmodule/constructionDecision/WjInfo/getCaseInfoForMap.do?timeType="+timeType+"&gridNumber="+gridNumber,
     dataType:"json",
     data:formInfo,
     success:function(data){
      dd=data;
     }
   });
   return dd;//
  }
//測試
  function test(){
   var data=getCaseInfoForMap();
   alert(data[0].caseId);
  }

//--------------------------------------------------------------------------------------------------------------------------------------------//
 //此種爲同步async:false,ajax執行不完不會return 
 function getCaseInfoForMap(){
   var formInfo=$("#firstForm").serialize();
   var dd="";
    $.ajax({
     type:"post",
     url:"<%=path %>/webmodule/constructionDecision/WjInfo/getCommCaseInfoCount.do?timeType="+timeType+"&gridNumber=110105217",
     dataType:"json",
     data:formInfo,
     async:false,
     success:function(data){
      dd=data; 
     }
   });
   return dd;
  }
//測試
  function test(){
   var data=getCaseInfoForMap();
   alert(data);
   
  }