javascript + asp 實現javascript跨域讀取xml檔案

a.html
 <script  >
 function getPeiLvData()
{
     var xmlHttpObj=createXMLHTTP();
     xmlHttpObj.onreadystatechange=function(){
         if (xmlHttpObj.readyState==4)
         {
            if (xmlHttpObj.status==200)
             {
                 alert(xmlHttpObj.responseText);xmlHttpObj=null;
             } } }
     xmlHttpObj.open("post","readXML.asp",true);
     xmlHttpObj.setRequestHeader('Content-type','application/x-www-form-urlencoded');
     xmlHttpObj.send(true);
}
 getPeiLvData();
 </script>

 readXML.asp
 <%@LANGUAGE="VBSCRIPT" CODEPAGE="936"%>
 <%response.charset="gb2312"%>
 <%
filePath="http://www.xx.com/xml/xx.xml"
 response.write getXML(filePath)
 function getXML(url)
 dim sttp
 set sttp=server.createobject("MSXML2.XMLHTTP")
 sttp.open "GET",url,false, "", ""
 sttp.send()
 if sttp.readystate<>4 then
 exit function
 end if
 getXML=sttp.responseBody
 set sttp=nothing
 end function
 %>