Robust Javascript Exception Handling

Question

I am developing a DHTML/Javascript application which relies on some advanced features (DOM manipulation, AJAX, Flash communication, and more). I'm very concerned about functionality -- if problems occur, even after the application is deployed, I want to make sure I know why and how to fix them -- and also, I want to make sure the user is able to continue using the application, possibly with reduced functionality if the exception was severe.

I currently have a logging and exception handling system built whereby functions can generate logs, and if an exception is caught, all logs are emailed to me. The system works well but I'd like to make it more robust. I'm looking for suggestions.

One idea I have is to wrap the body of every javascript function in a try/catch block and upon catching an exception, log the name of the function and then throw the error to the global handler. But that's a lot of code just to track down the function the exception occurred in.

Any ideas to make runtime exceptions easier to find and reproduce?

Answer 1

Rather than dealing with adding N try/catch blocks to N functions, it might be easier to use the window.onerror event.

JavaScript Kit has a series of examples you could use. Especially the 3rd:

window.onerror = function (msg, url, line) {
  alert('Error message: ' + msg + '\nURL: ' + url + '\nLine Number: ' + line);
  return true;
}

If you'd prefer a stack trace, you might check out Eric Wendelin's (or Luke Smith's update). It's one of the few I know of that attempts to work cross-browser.