Ajax同时执行两个request数据丢失问题

<script language="javascript">
var r1, r2;function init()
{
r1 = getRequest();
r2 = getRequest();
var url = path + "/vote/VoteAction.do?method=UpdateVoteResult&voteId="; s1(url + "1");
//alert("x");
s2(url + "2");
//alert("x");
}function s1(url)
{
r1.onreadystatechange = f1;
r1.open("post", url, true);
r1.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
r1.send(null);
}function s2(url)
{
r2.onreadystatechange = f2;
r2.open("post", url, true);
r2.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
r2.send(null);
}function f1()
{
if(r1.readyState == 4){
alert("class1:" + r1.responseText);
}
}function f2()
{
if(r2.readyState == 4){
alert("class2:" + r2.responseText);
}
}function getRequest()
{
var xmlHttp = false;
try{
xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
}catch(e){
try{
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}catch(e2){
xmlHttp = false;
}
}
if(!xmlHttp && typeof XMLHttpRequest != 'undefined'){
xmlHttp = new XMLHttpRequest();
}
return xmlHttp;
}
</script>
</head><body onload="init()">