js中一个函数获取另一个函数返回值问题

//此种为异步，还不等ajax赋完值，函数就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;//

}

//测试

function test(){

var data=getCaseInfoForMap();

alert(data[0].caseId);

}

//--------------------------------------------------------------------------------------------------------------------------------------------//

//此种为同步async:false,ajax执行不完不会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;

}

//测试

function test(){

var data=getCaseInfoForMap();

alert(data);

}