12 Jun
2013
12 Jun
'13
3:11 p.m.
I am not sure I understand what does last exception now contain that would be of use to us
--
Mohamed Ashraf
Sent with Sparrow (http://www.sparrowmailapp.com/?sig)
On Wednesday, June 12, 2013 at 9:58 AM, Rouslan Placella wrote:
> On 06/12/2013 07:50 AM, Mohamed Ashraf wrote:
> > I was researching about how to catch errors in javascript. I faced a
> > problem. due to the way javascript works for a try block to catch an
> > error it has to be within the context of execution which means in the
> > following code:
> >
> > try {
> > function f(){
> > throw new Error()
> > }
> > } catch (e) {}
> >
> > calling f(); the error will not be caught in the try block.
> > essentially what this means is that if we need to catch the errors
> > using try and catch blocks we need to wrap the inside of every
> > function with a try block. I am not sure how feasible is this idea but
> > it I am sure it would reduce code readability.
> >
> > The other option is using window.onerror which allows you to hook a
> > function that gets executed whenever an uncaught exception occurs.
> > This is obviously much simpler and less invasive and has an upside
> > that errors in any context anywhere will still be reported to the
> > hooked function. But there is a catch. which is that window.onerror
> > does not provide a stacktrace because it is executed in a different
> > context from the error itself. what it has access to is the line
> > number, file name and exception message.
> >
> > so my question is which method should I use, the surrounding all
> > functions by try blocks or using the window.onerror callback method?
> > how important is the stacktrace?
> >
>
>
> Some of my thoughts are:
>
> * Try/catch has a performance penalty
> * We need to be able to easily turn off the error reporting feature
> * Some/most function names in the stack trace are going to be useless as
> the production js code is minified.
> * The line numbers in the file will not be of much help either, I guess,
> unless we change the way that the files are minified (like forcing line
> breaks every few hundred characters).
> * If we do want the stack traces, given that we use jQuery, we could tap
> into it and whip up our own traces. For example (completely untested code):
>
> var lastException;
> (function ($) {
> var bind = $.fn.bind;
> $.fn.bind = function () {
> try {
> throw new Error;
> } catch (exception) {
> lastException = exception;
> }
> bind.apply({}, arguments);
> };
> })(jQuery);
>
> Later, lastException can be accessed from window.onerror. Of course,
> we'd have to tap into quite a few functions.
>
> To me it sounds like window.onerror is the winner here.
>
> Bye,
> Rouslan
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