What could be the reason why this XMLHttpRequest demo from Mozilla isn't functioning properly in Firefox 3?

Question

What could be the reason why this XMLHttpRequest demo from Mozilla isn't functioning properly in Firefox 3?

Having some trouble with getting the sample code from Mozilla to work with a REST web service in Firefox 3.0.10. Surprisingly, it works fine in IE 8!

Why is this not working?
Does IE 8 support XMLHttpRequest? Most examples I've seen use ActiveX allocation. What's the recommended approach? XMLHttpRequest seems more standardized.

Sample:

var req = new XMLHttpRequest();
req.open('GET', 'http://localhost/myRESTfulService/resource', false);    // throws 'undefined' exception
req.send(null);
if(req.status == 0)
  dump(req.responseText);

The open statement is throwing an exception with the description 'undefined'. Despite allocating the req object and running it in Firefox, it claims to be defined as an 'object' before calling open.

I also tried the asynchronous version of this with no success.

EDIT 2: Here is my latest code:

function createRequestObject() {
    if( window.XMLHttpRequest ) {
        return new XMLHttpRequest();
    }
    else if( window.ActiveXObject ) {
        return new ActiveXObject( "Microsoft.XMLHTTP" );
    }

    return null;
}

function handleResponse( req ) {
    document.writeln( "Handling response..." );   // NEVER GETS CALLED
    if( req.readyState == 0 ) {
        document.writeln( "UNITIALIZED" );
    }
    else if( req.readyState == 1 ) {
        document.writeln( "LOADING" );
    }
    else if( req.readyState == 2 ) {
        document.writeln( "LOADED" );
    }
    else if( req.readyState == 3 ) {
        document.writeln( "INTERACTIVE" ); 
    }
    else if( req.readyState == 4 ) {
        document.writeln( "COMPLETE" );
        if( req.status == 200 ) {
            document.writeln( "SUCCESS" );
        }
    }
}

document.writeln( "" );
var req = createRequestObject();

try {
    document.writeln( "Opening service..." );
    req.onreadystatechange = function() { handleResponse( req ); };
    req.open('POST', 'http://localhost/test/test2.txt', true);  // WORKS IN IE8 & NOT FIREFOX

    document.writeln( "Sending service request..." );
    req.send('');

    document.writeln( "Done" );
}
catch( err ) {
    document.writeln( "ERROR: " + err.description );
}

EDIT 3: Decided to rewrite this using jQuery. While jQuery runs smoothly in IE, it throws 'Undefined' when run from Firefox. Ensured that 'Enable JavaScript' is turned on in Firefox - which works fine on all other websites. Below is the jQuery code:

function handleResponse( resp ) {
    alert( "Name: " + resp.Name );
    alert( "URL: " + resp.URL );
}

$(document).ready( function() {
    $("a").click( function(event) {

        try {
            $.get( "http://localhost/services/ezekielservices/configservice/ezekielservices.svc/test", 
                   "{}",
                   function(data) { handleResponse( data ); },
                   "json" );
        } 
        catch( err ) {
            alert("'$.get' threw an exception: " + err.description);
        }

        event.preventDefault();
    });
} );    // End 'ready' check

Summary of Solution:

Lesson learned here. The issue was indeed cross-domain related. Testing the site locally (file system) making requests to a remote service caused the problem. Publishing the site under the same domain resolved this.

This situation highlights an important difference between IE and Firefox. When IE faces such scenarios, it prompts the user for permission for cross-domain calls. On the other hand, Firefox raises an exception. Though exceptions are acceptable, a more informative one would have been beneficial.

Appreciate everyone who assisted me through this problem.

javascript ajax firefox rest xmlhttprequest

Answer 1

Answer №1

If the request does not originate from the domain '', it will not work due to the same origin policy.

Update: A good status should be 200, not 0.

Check out and click on "stackoverflow test". It is using your code and working properly.

Here is the specific code snippet being used:

function test(){
    var req = new XMLHttpRequest();
    req.open('GET', 'index2.htm', false);    
    req.send(null);
    if(req.status == 200)
    alert("got some stuff back:"+req.responseText);
}

Answer 2

If the request does not originate from the domain '', it will not work due to the same origin policy.

Update: A good status should be 200, not 0.

Check out and click on "stackoverflow test". It is using your code and working properly.

Here is the specific code snippet being used:

function test(){
    var req = new XMLHttpRequest();
    req.open('GET', 'index2.htm', false);    
    req.send(null);
    if(req.status == 200)
    alert("got some stuff back:"+req.responseText);
}

Answer 3

Answer №2

Avoid using onreadystatechange with synchronous requests ('false'), instead place the handler immediately after the send() function. It appears that Firefox does not execute the onreadystatechange function with synchronous requests.

Click here for more information.

Answer 4

Avoid using onreadystatechange with synchronous requests ('false'), instead place the handler immediately after the send() function. It appears that Firefox does not execute the onreadystatechange function with synchronous requests.

Click here for more information.

Answer 5

Answer №3

If you want to optimize your code, consider using an asynchronous approach where one function initiates the request and another function manages the response.

function initiateRequest() 
{
   var httpReq;
   if (window.XMLHttpRequest) // For browsers like Firefox
   {
       httpReq = new XMLHttpRequest();
   } else if (window.ActiveXObject) { // For Internet Explorer
       httpReq = new ActiveXObject("Microsoft.XMLHTTP");
   }
   httpReq.onreadystatechange = function(){manageResponse(httpReq)};
   httpReq.open('POST','http://localhost/test/test2.txt',true);
   httpReq.send('');
}


function manageResponse(req)
{
    if(req.readyState == 4) {
        if(req.status == 200) {
            // Place handling logic here
            // req.responseText contains the returned string
        }
    }
}

This pattern is commonly used for AJAX calls in various browsers such as Firefox, IE, and Safari.

Note: Have you tried using Firebug? It's an excellent tool for debugging JavaScript.

UPDATE: You could also try out this revised code:

<html>
<head>
<script>
function outputResult(outStr) // A simple output function
{
    document.getElementById("output").innerHTML += "<br>" + outStr;
}

function handleResponse(request) {
    if( request.readyState == 0 ) {
        outputResult("UNINITIALIZED");
    }
    else if( request.readyState == 1 ) {
        outputResult("LOADING");
    }
    else if( request.readyState == 2 ) {
        outputResult("LOADED");
    }
    else if( request.readyState == 3 ) {
        outputResult("INTERACTIVE"); 
    }
    else if( request.readyState == 4 ) {
        outputResult("COMPLETE");
        if( request.status == 200 ) {
            outputResult(request.responseText);
        }
    }
}

function createRequest()
{
    var request = null;
    if(window.XMLHttpRequest) {
        request = new XMLHttpRequest();
    } else if(window.ActiveXObject) {
        request = new ActiveXObject("Microsoft.XMLHTTP");
    }
    return request;
}

function sendRequest()
{
    var request = createRequest();

    try {
        outputResult("Opening service...");
        request.onreadystatechange = function() { handleResponse(request); };
        request.open('POST', 'http://localhost/test/test2.txt', true);
        
        outputResult("Sending service request...");
        request.send('');

        outputResult("Done");
    }
    catch(err) {
        outputResult("ERROR: " + err.description);
    }
}
</script>
</head>
<body>
<div onclick="sendRequest();">test<br></div>
<div id="output">Output Here</div>
</body>
</html>

Please ensure that you point http://localhost/test/test2.txt to an existing file on your server.

If you're facing issues with the current implementation, it might be due to writing directly to the document, which can disrupt existing code. In this version, I am updating a specific div element instead.

Answer 6

If you want to optimize your code, consider using an asynchronous approach where one function initiates the request and another function manages the response.

function initiateRequest() 
{
   var httpReq;
   if (window.XMLHttpRequest) // For browsers like Firefox
   {
       httpReq = new XMLHttpRequest();
   } else if (window.ActiveXObject) { // For Internet Explorer
       httpReq = new ActiveXObject("Microsoft.XMLHTTP");
   }
   httpReq.onreadystatechange = function(){manageResponse(httpReq)};
   httpReq.open('POST','http://localhost/test/test2.txt',true);
   httpReq.send('');
}


function manageResponse(req)
{
    if(req.readyState == 4) {
        if(req.status == 200) {
            // Place handling logic here
            // req.responseText contains the returned string
        }
    }
}

This pattern is commonly used for AJAX calls in various browsers such as Firefox, IE, and Safari.

Note: Have you tried using Firebug? It's an excellent tool for debugging JavaScript.

UPDATE: You could also try out this revised code:

<html>
<head>
<script>
function outputResult(outStr) // A simple output function
{
    document.getElementById("output").innerHTML += "<br>" + outStr;
}

function handleResponse(request) {
    if( request.readyState == 0 ) {
        outputResult("UNINITIALIZED");
    }
    else if( request.readyState == 1 ) {
        outputResult("LOADING");
    }
    else if( request.readyState == 2 ) {
        outputResult("LOADED");
    }
    else if( request.readyState == 3 ) {
        outputResult("INTERACTIVE"); 
    }
    else if( request.readyState == 4 ) {
        outputResult("COMPLETE");
        if( request.status == 200 ) {
            outputResult(request.responseText);
        }
    }
}

function createRequest()
{
    var request = null;
    if(window.XMLHttpRequest) {
        request = new XMLHttpRequest();
    } else if(window.ActiveXObject) {
        request = new ActiveXObject("Microsoft.XMLHTTP");
    }
    return request;
}

function sendRequest()
{
    var request = createRequest();

    try {
        outputResult("Opening service...");
        request.onreadystatechange = function() { handleResponse(request); };
        request.open('POST', 'http://localhost/test/test2.txt', true);
        
        outputResult("Sending service request...");
        request.send('');

        outputResult("Done");
    }
    catch(err) {
        outputResult("ERROR: " + err.description);
    }
}
</script>
</head>
<body>
<div onclick="sendRequest();">test<br></div>
<div id="output">Output Here</div>
</body>
</html>

Please ensure that you point http://localhost/test/test2.txt to an existing file on your server.

If you're facing issues with the current implementation, it might be due to writing directly to the document, which can disrupt existing code. In this version, I am updating a specific div element instead.

Answer 7

Answer №4

Although the situation is unclear, it is important to inform you that a representative from Mozilla documentation is monitoring this closely. Any necessary adjustments to the documentation will be made once more information becomes available.

Answer 8

Although the situation is unclear, it is important to inform you that a representative from Mozilla documentation is monitoring this closely. Any necessary adjustments to the documentation will be made once more information becomes available.

Answer 9

Answer №5

At one point, I encountered a similar issue that turned out to be a simple mistake easily overlooked. Everything seemed to be working smoothly in Internet Explorer, but there were unexpected glitches when using Chrome and Firefox.

Initially, we mistakenly used Type="submit" instead of type="button". While this did not cause any issues in terms of functionality such as data updates, we kept receiving an HTTP: error 0 message in the alert box whenever we tried to access req.responseText. Implementing the following code snippet resolved the problem:

input type="button" name="btnEdit5" id="btnEdit5" value="Confirm" onClick="show_confirm()"

Answer 10

At one point, I encountered a similar issue that turned out to be a simple mistake easily overlooked. Everything seemed to be working smoothly in Internet Explorer, but there were unexpected glitches when using Chrome and Firefox.

Initially, we mistakenly used Type="submit" instead of type="button". While this did not cause any issues in terms of functionality such as data updates, we kept receiving an HTTP: error 0 message in the alert box whenever we tried to access req.responseText. Implementing the following code snippet resolved the problem:

input type="button" name="btnEdit5" id="btnEdit5" value="Confirm" onClick="show_confirm()"

Answer 11

Answer №6

Encountered a similar issue recently. The reason Internet Explorer functions while other browsers do not is due to IE allowing the file to be opened with a URL like "C:\xampp\htdocs\project3\project3.html", whereas other browsers convert it to a URL like "file:///C:/xampp/htdocs/project3/project3.html". This discrepancy arises because the domain of the PHP file must match that of the javascript file for IE to work properly, unlike in other browsers. To resolve this, ensure you are using a URL with "http://localhost/project3/project3.html" and pay attention to including localhost in the address. Furthermore, make sure your javascript call is referencing the PHP file through localhost.

Answer 12

Encountered a similar issue recently. The reason Internet Explorer functions while other browsers do not is due to IE allowing the file to be opened with a URL like "C:\xampp\htdocs\project3\project3.html", whereas other browsers convert it to a URL like "file:///C:/xampp/htdocs/project3/project3.html". This discrepancy arises because the domain of the PHP file must match that of the javascript file for IE to work properly, unlike in other browsers. To resolve this, ensure you are using a URL with "http://localhost/project3/project3.html" and pay attention to including localhost in the address. Furthermore, make sure your javascript call is referencing the PHP file through localhost.

Answer 13

Answer №7

Aside from the typical errors found on the client side, a major contributing factor to this issue is that the gecko engine specifically searches for the Access-Control-Allow-Origin in the header from the servlet. If it's missing, the communication will be halted resulting in a status=0 and statusText=null. Additionally, the moz-nullprincipal contributes to XML parsing errors, creating a lot of confusion. Fortunately, resolving this problem is simple:

response.setHeader("Access-Control-Allow-Origin","*");

Add this line in the servlet code and everything should work smoothly :-)

Answer 14

Aside from the typical errors found on the client side, a major contributing factor to this issue is that the gecko engine specifically searches for the Access-Control-Allow-Origin in the header from the servlet. If it's missing, the communication will be halted resulting in a status=0 and statusText=null. Additionally, the moz-nullprincipal contributes to XML parsing errors, creating a lot of confusion. Fortunately, resolving this problem is simple:

response.setHeader("Access-Control-Allow-Origin","*");

Add this line in the servlet code and everything should work smoothly :-)

Answer 15

Answer №8

Swap out this line for a new one

req.open('POST', 'http://localhost/test/test2.txt', true); // WORKS IN IE8 & NOT FIREFOX

Replace it with

req.open('GET', 'http://localhost/test/test2.txt', true); // WORKS IN IE8 & NOT FIREFOX

Answer 16

Swap out this line for a new one

req.open('POST', 'http://localhost/test/test2.txt', true); // WORKS IN IE8 & NOT FIREFOX

Replace it with

req.open('GET', 'http://localhost/test/test2.txt', true); // WORKS IN IE8 & NOT FIREFOX

What could be the reason why this XMLHttpRequest demo from Mozilla isn't functioning properly in Firefox 3?

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

Answer №8

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