Ajax won't get past readyState 1, why?

Question

I'm trying to get this function to work, which does a request for parameter url then sends the responseText to callback which is a function.

It seems that it only gets to readyState 1 (thanks to the Firebug commands).

Here it is:

function Request(url, callback){
if (window.XMLHttpRequest) { // Mozilla, Safari, ...
    httpRequest = new XMLHttpRequest();
} else if (window.ActiveXObject) { // IE
    httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
} else{
    return false;
}
httpRequest.onreadystatechange = function(){
    console.log(httpRequest.readyState);
    if (httpRequest.readyState == 4) {
        callback(httpRequest.responseText);
    }
};
console.log(httpRequest, url);
httpRequest.open('GET', url, true);
httpRequest.send(null);
}

Solution 1

I workarounded this problem assigning onload event instead of onreadystatechange:

function Request(url, callback){
if (window.XMLHttpRequest) { // Mozilla, Safari, ...
    httpRequest = new XMLHttpRequest();
} else if (window.ActiveXObject) { // IE
    httpRequest = new ActiveXObject("Microsoft.XMLHTTP");
} else{
        return false;
}

var readyStateChange = function(){
    console.log(httpRequest.readyState);

    if (httpRequest.readyState == 4) {
                callback(httpRequest.responseText);
    }
};


if (isFirefox && firefoxVersion > 3) {
    httpRequest.onload = readyStateChange;
} else {
    httpRequest.onreadystatechange = readyStateChange;
}

console.log(httpRequest, url);
httpRequest.open('GET', url, true);
httpRequest.send(null);
}

Solution 2

Check that the URL in question does actually respond by visiting it directly in the browser.

Test with a different browser do you get the same result.

Use some form of HTTP monitor to watch the client to server conversation (my favorite is Fiddler)

Solution 3

Possibly the Ajax request doesn't return data (so, a server side error of some kind). Try enabling the option 'show XMLHttpRequests' in the firebug console, to check for this.

Comments

[kennyisaheadbanger]

Well it's already on and I log the http object and inspecting it gives me readyState 4, but the event is not being called. Also the page returns data properly

[KooiInc]

Tried logging my own xmlHTTP lib function in FF, no problem. In my case I use => if (httpRequest.readyState < 4) {console.log(...);} else { [exec the callback]}.

[KooiInc]

Furthermore: my readystatechange handler is defined after the send method is called.

[Mirko Cianfarani]

Error console: Uncaught ReferenceError: isFirefox is not defined