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Is there a way to tell a browser, Opera or Chrome for example, not to stop scripts execution if it encounters an unhandled exception? I just need to test some JS scripts in browser but the page also includes some code for another (non-regular browser) execution environment hence modifying code as wrapping with try/catch isn't practical.

For Chrome I've tried to put code that sets a handler function to window.onerror which just returns true, then error didn't appear in console but execution of scripts aborted anyway.

To be specific the page contains code for Appcelerator Titanium platform, but I'm only testing general jQuery code so I'd like to do it in a browser.

Ilya I
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    have you already wrapped your functions in try/catch? just asking. – kpcrash Mar 27 '12 at 19:00
  • As I said I shouldn't change any scripts that the page includes. – Ilya I Mar 27 '12 at 19:09
  • Correct, but if you're calling the functions in from an external source, you can still wrap those calls and it should stop the browser from spewing alerts on errors. – kpcrash Mar 27 '12 at 19:10
  • How do I wrap code which is included by html script tag? – Ilya I Mar 27 '12 at 19:18
  • That would imply that the code you're including executes blindly - meaning, it's set for document.ready vs. you calling an external function directly from your page/script - in which case, you're kinda stuck. – kpcrash Mar 27 '12 at 19:20

2 Answers2

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If you call the suspect code in deferred fashion

setTimeout(THIS_MIGHT_THROW, 0)

then any errors thrown will terminate the "thread" or "micro-task", but not affect the rest of your execution.

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As practical as your idea may seem, in reality it is impossible to enforce.

Comparatively, the Java programming language forces you to handle checked exceptions (exceptions you can recover from), while unchecked exceptions (such as RuntimeException - exceptions you cannot recover from) can just happen normally at runtime outside of your control. Since they are essentially unrecoverable, your program has to stop.

Exceptions raised from the JS JVM are, unlike in java, impossible to separate in checked and unchecked categories. Because there's no such a distinction, it is not possible to avoid the script to stop.

What if you divided function/infinity? How should you recover from that? To each distinct scenario exists a distinct answer. This is why the only remaining and valid response to your concern is to use try catch block each time you're afraid an Exception will happen and stop your code, and handle it specifically to that situation.

As for the window.onerror event handler, it is irrelevant for this matter because it does not catch runtime exceptions, it catches the error that is raised when the original exception is not caught in a try catch block. That's why you get a magnificient "Uncaught exception: xxxxx" appended to the actual, original, exception message. The exception already happened, your script is already stopped, all you can do is display it the way you want at this point.

Sebas
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