Is it possible to catch an error when using JSONP with jQuery? I've tried both the $.getJSON and $.ajax methods but neither will catch the 404 error I'm testing. Here is what I've tried (keep in mind that these all work successfully, but I want to handle the case when it fails):
jQuery.ajax({
type: "GET",
url: handlerURL,
dataType: "jsonp",
success: function(results){
alert("Success!");
},
error: function(XMLHttpRequest, textStatus, errorThrown){
alert("Error");
}
});
And also:
jQuery.getJSON(handlerURL + "&callback=?",
function(jsonResult){
alert("Success!");
});
I've also tried adding the $.ajaxError but that didn't work either:
jQuery(document).ajaxError(function(event, request, settings){
alert("Error");
});
Here's my extensive answer to a similar question.
Here's the code:
jQuery.getJSON(handlerURL + "&callback=?",
function(jsonResult){
alert("Success!");
})
.done(function() { alert('getJSON request succeeded!'); })
.fail(function(jqXHR, textStatus, errorThrown) { alert('getJSON request failed! ' + textStatus); })
.always(function() { alert('getJSON request ended!'); });
It seems that JSONP requests that don't return a successful result never trigger any event, success or failure, and for better or worse that's apparently by design.
After searching their bug tracker, there's a patch which may be a possible solution using a timeout callback. See bug report #3442. If you can't capture the error, you can at least timeout after waiting a reasonable amount of time for success.
Detecting JSONP problems
If you don't want to download a dependency, you can detect the error state yourself. It's easy.
You will only be able to detect JSONP errors by using some sort of timeout. If there's no valid response in a certain time, then assume an error. The error could be basically anything, though.
Here's a simple way to go about checking for errors. Just use a success flag:
var success = false;
$.getJSON(url, function(json) {
success = true;
// ... whatever else your callback needs to do ...
});
// Set a 5-second (or however long you want) timeout to check for errors
setTimeout(function() {
if (!success)
{
// Handle error accordingly
alert("Houston, we have a problem.");
}
}, 5000);
As thedawnrider mentioned in comments, you could also use clearTimeout instead:
var errorTimeout = setTimeout(function() {
if (!success)
{
// Handle error accordingly
alert("Houston, we have a problem.");
}
}, 5000);
$.getJSON(url, function(json) {
clearTimeout(errorTimeout);
// ... whatever else your callback needs to do ...
});
Why? Read on...
Here's how JSONP works in a nutshell:
JSONP doesn't use XMLHttpRequest like regular AJAX requests. Instead, it injects a <script> tag into the page, where the "src" attribute is the URL of the request. The content of the response is wrapped in a Javascript function which is then executed when downloaded.
For example.
JSONP request: https://api.site.com/endpoint?this=that&callback=myFunc
Javascript will inject this script tag into the DOM:
<script src="https://api.site.com/endpoint?this=that&callback=myFunc"></script>
What happens when a <script> tag is added to the DOM? Obviously, it gets executed.
So suppose the response to this query yielded a JSON result like:
{"answer":42}
To the browser, that's the same thing as a script's source, so it gets executed. But what happens when you execute this:
<script>{"answer":42}</script>
Well, nothing. It's just an object. It doesn't get stored, saved, and nothing happens.
This is why JSONP requests wrap their results in a function. The server, which must support JSONP serialization, sees the callback parameter you specified, and returns this instead:
myFunc({"answer":42})
Then this gets executed instead:
<script>myFunc({"answer":42})</script>
... which is much more useful. Somewhere in your code is, in this case, a global function called myFunc:
myFunc(data)
{
alert("The answer to life, the universe, and everything is: " + data.answer);
}
That's it. That's the "magic" of JSONP. Then to build in a timeout check is very simple, like shown above. Make the request and immediately after, start a timeout. After X seconds, if your flag still hasn't been set, then the request timed out.
I know this question is a little old but I didn't see an answer that gives a simple solution to the problem so I figured I would share my 'simple' solution.
$.getJSON("example.json", function() {
console.log( "success" );
}).fail(function() {
console.log( "error" );
});
We can simply use the .fail() callback to check to see if an error occurred.
Hope this helps :)
If you collaborate with the provider, you could send another query string parameter being the function to callback when there's an error.
?callback=?&error=?
This is called JSONPE but it's not at all a defacto standard.
The provider then passes information to the error function to help you diagnose.
Doesn't help with comm errors though - jQuery would have to be updated to also callback the error function on timeout, as in Adam Bellaire's answer.
Seems like this is working now:
jQuery(document).ajaxError(function(event, request, settings){
alert("Error");
});
I use this to catch an JSON error
try {
$.getJSON(ajaxURL,callback).ajaxError();
} catch(err) {
alert("wow");
alert("Error : "+ err);
}
Edit: Alternatively you can get the error message also. This will let you know what the error is exactly. Try following syntax in catch block
alert("Error : " + err);
Mayby this works?
.complete(function(response, status) {
if (response.status == "404")
alert("404 Error");
else{
//Do something
}
if(status == "error")
alert("Error");
else{
//Do something
}
});
I dont know whenever the status goes in "error" mode. But i tested it with 404 and it responded
you ca explicitly handle any error number by adding this attribute in the ajax request:
statusCode: {
404: function() {
alert("page not found");
}
}
so, your code should be like this:
jQuery.ajax({
type: "GET",
statusCode: {
404: function() {
alert("page not found");
}
},
url: handlerURL,
dataType: "jsonp",
success: function(results){
alert("Success!");
},
error: function(XMLHttpRequest, textStatus, errorThrown){
alert("Error");
}
});
hope this helps you :)
I also posted this answer in stackoverflow - Error handling in getJSON calls
I know it's been a while since someone answerd here and the poster probably already got his answer either from here or from somewhere else. I do however think that this post will help anyone looking for a way to keep track of errors and timeouts while doing getJSON requests. Therefore below my answer to the question
The getJSON structure is as follows (found on http://api.jqueri.com):
$(selector).getJSON(url,data,success(data,status,xhr))
most people implement that using
$.getJSON(url, datatosend, function(data){
//do something with the data
});
where they use the url var to provide a link to the JSON data, the datatosend as a place to add the "?callback=?" and other variables that have to be send to get the correct JSON data returned, and the success funcion as a function for processing the data.
You can however add the status and xhr variables in your success function. The status variable contains one of the following strings : "success", "notmodified", "error", "timeout", or "parsererror", and the xhr variable contains the returned XMLHttpRequest object
(found on w3schools)
$.getJSON(url, datatosend, function(data, status, xhr){
if (status == "success"){
//do something with the data
}else if (status == "timeout"){
alert("Something is wrong with the connection");
}else if (status == "error" || status == "parsererror" ){
alert("An error occured");
}else{
alert("datatosend did not change");
}
});
This way it is easy to keep track of timeouts and errors without having to implement a custom timeout tracker that is started once a request is done.
Hope this helps someone still looking for an answer to this question.
Related
I'm using jQuery to handle Ajax-calls.
I've noticed that, about 5% off the time, the ajax call fails. To make sure I get a good understanding of what's going wrong, I use this code:
$.ajax({
type:'POST',
url:'somepage.php',
data:{somedata:somedata},
success:function (data) {
var IS_JSON = true;
try
{
var newdata = jQuery.parseJSON(data);
}
catch(err)
{
IS_JSON = false;
}
if(IS_JSON)
{
//this is the part where a correct response is handled
}
else
{
//In case somepage.php gives a php-error, I put the exact error (=data) in the error-table at error.php.
window.location = "error.php?errorstring="+data;
}
},
error:function (XMLHttpRequest, textStatus, errorThrown) {
//In case the ajax errors, I store the response (timeout, error, ...) in the database at error.php
window.location = "error.php?errorstring="+textStatus;
}
});
"Good" responses contain JSON, which I parse. If it's not JSON (for example just raw text from an php error) I don't try to parse it, but store the error in my database.
I would understand errors containing php errors that occured on somepage.php (since it's quiet a large page), but I'm supprised that the main errors I get, are errors of the ajax failing. The response data is just "error".
Anyone knows what the cause could be? What causes ajax-calls to fail? It's not a timeout, and it's also nothing like that somepage.php wasn't found or something. It's also not an error on somepage.php, since in that case, the Ajax-call would be successful, and the php-error would be logged in my database.
Edit: I used this obfuscator to make the script a little harder to read... Don't know if this could be causing the errors...
You should set dataType: 'json' in your ajax call. Coz if your not setting this up and your expecting a json result, the result will be treated as 'string' by default.
I need to detect if my service is available in the moment.
But, for some reason, I receive success in ajax() function when I try to reach some of the service methods even if the service is turned off.
I get an html page with 404 message as data in the success field.
My best guess is to use typeof(data) and compare it with string type.
But I think there must be a better solution.
Nothing special just $.ajax()
$.ajax({
url: '../Services/Service.svc/getItems',
data: {},
error: function (error) {
},
success: function (data, status, xhr) {
},
datatype: "json",
});
Going with the info you provided.
If you are in control of the service (ie: you built it) then you could make the webserver return a 503 code when the service is unavailable. This is something the webserver should do when your service is down.
If not, then you need to check for the 404 error code instead that you are receiving right now and handle it gracefully in your code.
I'm assuming you are using jQuery for the client since you refer to the ajax() call. Here is a basic example to check the errorcode in the fail callback:
var serviceRequest = $.ajax(...);
serviceRequest.done(function(returnedData) {
// Service is active and returning data.
});
serviceRequest.fail(function (xhr) {
if(xhr.status == 404) {
// handle this.
}
if(xhr.status == 503) {
// handle this.
}
});
Why you are receiving a 404 and hitting the success callback is something I have never seen before.
I a javascript function which sends an ajax request. Note that the server might return an error even if "everything seems to be ok" which means that there might be an error information in the handler of success:
function sendAjaxRequest(){
$.ajax({
type: "GET",
url: "/123",
success: function(data){
//there might and might not an error in data
if(data.error_exists){
retryIfError(data);
} else{
//everything is ok for sure
}
},
error: function(xhr, textStatus, errorThrown){
//there is the error for sure
retryIfError(xhr);
}
});
}
function retryIfError(data){
var error = data.error_list # the array of error messages
// ... what should I do further?
}
The reason is that success: function(data) might have an error is that the server uses begin ... rescue operators to suppress them. Is that the right approach?
The second question:
So the goal is to send sendAjaxRequest() until there are no errors anymore. How do I do that? Of course, I want also restrict the amount of sending sendAjaxRequest() requests, but I think it will be trivial and I'll take care of it by myself.
What about calling the function again? you can add a counter as well.
error: function(xhr, textStatus, errorThrown){
if(i<3)
sendAjaxRequest(i++);
}
And use.
var i=0;
My calls to $.post are not working all over my code. I'm not sending the request to other domains and, actually, I'm doing everything localhosted. My localhost alias was automatically defined by the Mac OS X 10.8 as ramon.local and I'm requesting from http://ramon.local/linkebuy_0.7/resourceX to http://ramon.local/linkebuy_0.7/resourceY. There are no errors on Chrome's console.
The server side doesn't receive the request and I can check it by accessing directly from the browser (typing the URL).
It's not just one call that is not working, none of them are. They were all working days ago and I'm suspicious that I accidentally changed something on my local settings. What could it be?
Here's an example of what I'm facing:
$.post(
<<CORRECT URL INSIDE THE DOMAIN>>,
{},
function(response) {
console.log('THIS SHOULD BE PRINTED ON CONSOLE');
alert('THIS SHOULD BE POPPED UP');
}
);
I don't get the alert, neither the console message while running the code above. So I tried the following:
$.support.cors = true;
$.ajax({
url: "http://ramon.local/linkebuy_0.7",
dataType: "json",
type: "GET",
crossDomain: true,
success: function (data) {
console.log(data);
},
error: function (xhr, status, error) {
alert(error + " - " + status);
}
});
I just came with $.support.cors = true; and crossDomain: true to check if it was a cross domain issue. So I was alerted No Transport - error same way as before.
What can I do to solve that?
Thanks in advance.
Try this and see if you are getting any alert:
// Assign handlers immediately after making the request,
// and remember the jqxhr object for this request
var jqxhr = $.post("your url", function() {
alert("success");
}).success(function() {
alert("second success");
}).error(function() {
alert("error");
}).complete(function() {
alert("complete");
});
// perform other work here ...
// Set another completion function for the request above
jqxhr.complete(function() {
alert("second complete");
});
Well, I solved the problem in a very strange way.
I deleted the JQuery file and downloaded it again, replacing the old one. Happens it worked out.
So, if you're:
Making AJAX requests that are not cross-domain;
Using JQuery for it (e.g. $.post, $.get, etc);
Getting No Transport AJAX error
Then re-download and replace you're JQuery source.
Else, if you're making cross-domain requests (not this case), then look for JSONP and try to set $.support.cors = true; at the beginning of you're code.
Thanks everyone for the comments and answers.
My problem happens to be the error, I am attempting to produce an error, in this case the error being hiding the loading symbol and showing a refresh button in order for the user to reload the page to see if the data loads this time.
$(document).ready(function () {
$('#busy').show();
$(document).bind('deviceready', function () {
var today = $('#todaysong');
$.ajax({
url: 'my url',
dataType: 'jsonp',
jsonp: 'jsoncallback',
timeout: 5000,
success: function (data, status) {
$.each(data, function (i, item) {
var song = '<name>' + item.name + '</name>' + '<artist>' + item.artist + '<br></artist>';
$('#busy').hide();
today.append(song);
});
},
error: function (error) {
$('#busy').fadeOut();
$('#reload').fadeIn();
}
});
});
});
This is my code, could someone advise on what I am doing wrong, I've tried a few things and cannot seem to get it to work, also would I make it so said button was able to refresh this individual piece of code?
Thanks a lot.
In order to debug your code:
Are you generating an error on your own? Is it really an error? Track your request via Firebug or ...
Be sure about running the error function. Again try Firebug or such things to set break points.
Check the JavaScript console for being sure there is no any of damn JavaScript error. And again Firebug error console.
Without seeing other details it is difficult to suggest.
Still I'm trying.. Check the IDs of the elements you have mentioned is same as they are in HTML. Check in HTML that one id is not assigned to more than one element.
In the AJAX code remove jsonp: 'jsoncallback', for a while and test if it is working.
error(jqXHR, textStatus, errorThrown)
A function to be called if the request fails. The function receives
three arguments: The jqXHR (in jQuery 1.4.x, XMLHttpRequest) object, a
string describing the type of error that occurred and an optional
exception object, if one occurred. Possible values for the second
argument (besides null) are "timeout", "error", "abort", and
"parsererror". When an HTTP error occurs, errorThrown receives the
textual portion of the HTTP status, such as "Not Found" or "Internal
Server Error." As of jQuery 1.5, the error setting can accept an array
of functions. Each function will be called in turn. Note: This handler
is not called for cross-domain script and JSONP requests. This is an
Ajax Event.
Where the important part in this case is;
Note: This handler is not called for cross-domain script and JSONP
requests.
Quote from the API documentation of jQuery.ajax.
You should instead be using jsonpCallback.