ajax的一点小问题

Question

function getXmlHttpObj()
{
if (window.XMLHttpRequest) { // Mozilla, Safari,...
            http_request = new XMLHttpRequest();
            if (http_request.overrideMimeType) {
                http_request.overrideMimeType('text/xml');
            }
        } else if (window.ActiveXObject) { // IE
            try {
                http_request = new ActiveXObject("Msxml2.XMLHTTP");
            } catch (e) {
                try {
                    http_request = new ActiveXObject("Microsoft.XMLHTTP");
                } catch (e) {}
            }
        }
return http_request;
}
xml_http.onreadystatechange=function(){
if (xml_http.readyState==4)
{
document.getElementById("aa").value=xml_http.responseText;
}
}
xml_http.open('POST','aa.asp',true);
xml_http.setRequestHeader("Content-Type","application/x-www-form-urlencoded") 
xml_http.send("aa=aaaa");
aa.asp
response.write("testtest");//(我不太懂ASP。希望没写错输出。)

Answer 1

xml_http.onreadystatechange=function(){上面加一句var xml_http=getXmlHttpObj();