JS一个ajax的小问题

Question

<script>
window.onload=function(){
var oBtn=document.getElementById('btn1');
oBtn.onclick=function(){
var oAjax=new XMLHttpRequest();
oAjax.open('GET','a.txt',true);
oAjax.send();
oAjax.onreadystatechange=function(){
if(oAjax.readyState==4){ 
if(oAjax.status==200)
{
alert('成功');
}
else{
alert('失败');
}
}   
};
};
};
</script>
这是页面的JS，页面有一个读取按钮。然后用IIS7.5，把这个页面和a.txt都放到了C:\inetpub\wwwroot里面。a.txt里面有字符，就abc。但是怎么运行后点击页面的读取，是弹出失败呢？不知道问题出了哪了。。请教各位~！

Answer 1

oAjax.send(); 放到后面试试<script>
window.onload=function(){
    var oBtn=document.getElementById('btn1');
    oBtn.onclick=function(){
            var oAjax=new XMLHttpRequest();    
            oAjax.open('GET','a.txt',true);
            
            oAjax.onreadystatechange=function(){
                if(oAjax.readyState==4){ 
                    if(oAjax.status==200)
                    {
                        alert('成功');
                        }
                        else{
                            alert('失败');
                            }
                    }   
                }; 
                oAjax.send();
        };
    };
</script>

Answer 2

LZ试试把oAjax.open('GET','a.txt',true);里a.txt换成URL的形式？