get error message from jquery's eventData object - javascript

I currently have a javascript error handler like this:
window.onerror = function(msg, url, line){ //stuff }};
But I would like to be able to use jquery to attach to onerror like so:
$(window).error(function(evtData){//stuff});
My question is, from jquery's eventData object, how can i get the error's message, url, and line number, as I did in the non-jquery function?
Thanks in advance.

From jQuery docs.
Note: A jQuery error event handler should not be attached to the
window object. The browser fires the window's error event when a
script error occurs. However, the window error event receives
different arguments and has different return value requirements than
conventional event handlers. Use window.onerror instead.
Refernce: http://api.jquery.com/error/

Related

what is this usage of alert in javascript?

Here is a xss code:
<img src=x onerror="javascript:window.onerror=alert;throw 1">
I can't understand the usage of alert here. Why we don't need parentheses after the alert? And I can't understand the behavior of browser. The browser will pop up a box and dislplay Uncaught 1. It looks like that the browser first pop up an alert box and then fill the exception string into the box. However, I am not quite sure how this happens. BTW, I tested this in chrome.
The window.onerror itself is a function. You can say it as a function name or better, function reference. And alert is also a name of the function, which can be called as funtion reference.
So, they are mapping the onerror with alert, i.e., when the onerror event takes place, there will be an alert.
The window.onerror being an event handler, and alert is something that alerts whatever sent into the parameter, now the onerror event handler sends the event information to the alert and yes, you get what's the error, when an error occurs.
More information about parameters and working of window.onerror. Their syntax is:
window.onerror = funcRef;
Where the funcRef is referred to alert().

Chrome not recognizing function arguments correctly

I have wrote some cross browser code for adding event listeners, then chrome started being funky, anyone know why this is happening?
Add Event listener code:
function addEventListener(Elm,Type,Func)
{
if(Elm.attachEvent)
Elm.attachEvent((Type.substr(0,2) == 'on' ? Type : 'on'+Type),Func);
else
Elm.addEventListener(Type,Func);
}
Code calling the method:
addEventListener(window,'load',SetSize);
addEventListener(window,'resize',SetSize);
Error:
Uncaught TypeError: Object load has no method 'addEventListener'
You can very clearly see that I have passed the arguments in the correct order yet they are not interpreted in said order..
You have overwritten window.addEventListener.
The native signature is: event_name, callback but yours is: object, event_name, callback.
Change the name of your function addEventListener or namespace it, like my_framework.addEventListener
You have redefined window.addEventListener. Anything you declare in the global namespace basically belongs to window, so:
function addEventListener(...) {
}
is the same as:
window.addEventListener = function(...) {
}
The argument signature for the native addEventListener is eventName, listener, but you have Elm, Type, Func.
Then inside your function body, you are doing Elm.addEventListener and passing it 'load' and SetSize. In that call, it calls your function again (because Elm is window) and this time, it attempts to call addEventListener on the string 'load', which won't work because a string doesn't have that method.
Change the name of your function, or namespace it, and it should work.
I would say the window object has not .attachEvent or .addEventListener.
This may caused because your function is named addEventListener and has overwritten the window.addEventListener()

Javascript: Errors arent being displayed on event listeners

I have a problem that is driving me crazy. I have two event listeners that appear to be identical. The are being called with the same scope but at different times. I have been using chromes debugger tool to step through them. The first one will throw an error
TypeError: Object 1 has no method 'get'
But the second example simple stops executing
el.on("change:one", function() {
debugger;
a = 1;
a.get();
});
el.on("change:two", function() {
debugger;
a = 1;
a.get();
});
I understand that simple asking why is this happening probably needs a detailed explanation of all the libraries being used etc, so my question is:
Is it possible to not display errors thrown by javascript, and how would I be able to detect whether something is overriding the error reporting functionality
NOTE: In both examples I have determined that window.onerror is null
Backbone invokes event handlers synchronously and doesn't catch handler exceptions. So if you had code that looked like:
el.trigger('change:one'); // handler will throw exception
el.trigger('change:two'); // won't execute
The change:two event will never get triggered, resulting in your change:two handler never getting invoked.

How to manully trigger an ajaxComplete event

Using Jquery I need to trigger a ajaxComplete event.
At the moment I'm using this code with no success
$.getJSON(assetUrl, function (data) {
...
$.trigger("ajaxComplete");
With Error:
TypeError: 'undefined' is not a function (evaluating '$.trigger("ajaxComplete")')
Any idea what I'm doing wrong? Thanks
The ajaxCompleted event is fired on the DOM, and you will need to call the trigger method on a jQuery wrapper element: $(document).trigger(...), for example.
There is not static function "trigger" on the jQuery object (that's what the error message is telling you), you might use $.event.trigger - though I fear that's internal.
However, you won't need to do it manually; getJSON does trigger the event itself. For aborting a running ajax request, see the abort method of XHR objects.
You can define a global jQuery ajaxComplete (and ajaxError) function that will run on document ready and after every completed ajax request. You can define the ajaxComplete function on the intial page load (or whenever really) like this:
$(function(){
$(document).ajaxComplete(function(){
// on complete code
}).ajaxError(function(){
// on error code
});
});
To call this event handler at any time, just execute the following:
$(document).triggerHandler('ajaxComplete');
If anybody else is looking at this, the correct way to manually trigger ajaxComplete is $(document).trigger('ajaxComplete', [xhr, settings]);
It's probably important to pass the xhr object to the ajaxComplete trigger event, as the event handler might need it.
However, you only need this, if you're not making your requests through jquery, since jquery handles this automatically for you.

JQuery error property for error handler

I'm just playing around for the first time with jQuery's ajax functionality. I wanted to add a function that could handle any errors. So, in one of my client javascript blocks, I added the following line:
<script type="text/javascript">
....
$.ajax({ error: function () { alert('boo'); } })
....
</script>
I expected that this would bind the error handler, so that when an error occurs, it would fire the anonymous function included.
What happens instead though, is that it immediately fires the function on page load, as soon as it parses this line of code.
What am I doing wrong? What is the proper way to bind the ajax error handler?
I'm not sure if I understood your question correctly, let me know if I've misunderstood.
I assume that you are trying to create a generic ajax call error handler? If that's the case, you have got the wrong idea.
Are you are just trying to bind the event handler? In this case, you are executing it.
I would recommend you read and check out the examples on these jQuery API reference docs:
API/1.3/Events
Ajax/jQuery.ajax
Also check out the post link provided by F.Aquino and this SO post: JavaScript Exception Handling.
This is could be helpful too: Handling AJAX Errors With jQuery.
You want to change the global settings. Check jQuery documentation.
$.ajaxSetup({
error: function () { alert('boo'); }
});

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