function MakeRequest(url, timeout,
onCompleteCallback, onTimeoutCallback)
{
var completeCallback = onCompleteCallback;
var timeoutCallback = onTimeoutCallback;
var xmlHttp=createXMLHttpRequest();
if (xmlHttp)
{
xmlHttp.onreadystatechange = function()
{
if (xmlHttp.readyState == 4)
{
window.clearTimeout(timeoutId);
if (xmlHttp.status == 200 ||
xmlHttp.status == 304)
{
completeCallback(
xmlHttp.responseText);
}
}
};
xmlHttp.open("GET",url,true);
var timeoutId =
window.setTimeout(function()
{
if (callInProgress(xmlHttp))
{
xmlHttp.abort();
timeoutCallback('timeout');
}
} , timeout);
xmlHttp.send(null);
}
}
function callInProgress(xmlHttp)
{
switch ( xmlHttp.readyState )
{
case 1, 2, 3:
return true;
break;
// Case 4 and 0
default:
return false;
break;
}
}
function createXMLHttpRequest() {
if(window.XMLHttpRequest) {
try {
xmlHttpRequest = new XMLHttpRequest();
} catch(e) { return null; }
} else if(window.ActiveXObject) {
try {
xmlHttpRequest =
new ActiveXObject("Msxml2.XMLHTTP");
} catch(e) {
try {
xmlHttpRequest =
new ActiveXObject("Microsoft.XMLHTTP");
} catch (e) { return null; }
}
} else return null;
return xmlHttpRequest;
}
I then wanted to call a .Net HttpHandler, and lets just say for arguments sake that the htp handler looks like this
public class Handler : IHttpHandler
{
public void ProcessRequest (HttpContext context)
{
System.Threading.Thread.Sleep(6000);
context.Response.ContentType = "text/plain";
context.Response.Write(Guid.NewGuid().ToString());
}
public bool IsReusable
{
get
{
return false;
}
}
}
so the call from javascript would simply look something like this
MakeRequest(
'Handler.ashx?cookie=abcd&another=xyz',
20000, onRequestComplete,
onRequestTimeout);
function onRequestTimeout(response)
{
alert('timeout');
}
function onRequestComplete(response)
{
alert(response);
}
The problem as I found out through good old wikipedia relates to the internet explorers caching of the "GET" http command as described in this article on HMLHttpRequest.
As discussed in the article, there are a number of ways around this, switch to using POST or ensure that you switch the caching off in the http headers. I chose the former.
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