Due to the large amount of code that ends up being run as a direct consequence of user-interaction on a webpage, allowing developers to catch all errors that are raised within event handlers added by zepto allows significantly improved debugging ability (particularly when coupled to a service like Airbrake or Bugsnag).
Obviously this is no substitute for handling errors locally; but it does significantly help with tracking down hard to find problems and unexpected exceptions.
This patch was inspired by a similar change made to ember.js emberjs/ember.js@99125d9...539f5a1#L0R40 (MIT license).
Add a global error handler
I don't think this is an issue, exceptions are thrown and should pop up in the debugger of your browser, no? I'm unsure about the specific use case here. Feel free to reopen with specific examples.
At work we used an exception tracker (there are a few, https://bugsnag.com/, https://airbrake.io, etc.) so that exceptions that happen in production can still be tracked.
Without a change like this, it's basically impossible to get enough information from a crash for an exception report to be useful. The installer you get if you visit https://intro.linkedin.com/ on an iPhone is using this patch.