Ajax problem

[theS70RM]

hi guys,

My code suddenly stopped working

here it is:


[HTML] function Ajax(page,data){

page = "includes/" + page;

var xmlHttp;
try
{
// Firefox, Opera 8.0+, Safari
xmlHttp=new XMLHttpRequest();
}
catch (e)
{
// Internet Explorer
try
{
xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e)
{
try
{
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
}
catch (e)
{
alert("Your browser does not support AJAX!");
return false;
}
}
}

var output;

xmlHttp.onreadystatechange=function()
{
if(xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
{
output = xmlHttp.responseText;
}
}

xmlHttp.open("POST",page,false);
xmlHttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
xmlHttp.send(data);


return output;

}[/HTML]


It works in firefox 2 (with firebug installed and enabled) but onreadystatechange doesnt seem to get called in IE (7 and before) and firefox 3.

Can anyone see why?? It has been working fine and I dont think ive changed this function but after an afternoon of debugging ive narrowed it down to this error. I also just tried replacing the "output = xmlHttp.responseText;" line to use a callback function like most online examples do, but still no joy.


Cheers

Andy

[acoder]

You're making a synchronous request as opposed to an asynchronous one. Are you sure that's what you want?

[theS70RM]

is that because im making the ajax function return the output from the request rather than using a callback function?

I think its ok that way for what im doing as its processing a form and the page is frozen till the action is complete anyway...

Not my main problem though, and thats that onreadystate doesnt get called anymore.

cheers for the response

Andy

[acoder]

If it's synchronous, the onreadystatechange will never fire, so output won't be set. Return the responseText directly after send() in place of 'output'.

[theS70RM]

ok, im a little lost then.

Thanks, that works by the way!

How would you make this function asynchronous?

[acoder]

Since it's synchronous, it never needs to let you know when it's complete via onreadystatechange. You'll know when the browser stops hanging. It stops at send() and waits until the request is complete, so you can safely return responseText after it, a bit like how a prompt/alert is modal.

To make it asynchronous, use "true" for the last parameter of the open() method.

[theS70RM]

ah ok, i think i understand now.

Thanks for your help!

[acoder]

No problem at all, you're welcome :)