onerror and onunhandledrejection/onrejectionhandled could use some nice developer-friendly examples

I notice that these features aren't really summarized anywhere developer-readable.

This is kind of a good first bug. Coming up with nice examples is an art. For promise rejection events, you can draw inspiration from https://nodejs.org/api/process.html#process_event_unhandledrejection. In all cases, I think it would be ideal to show use of something like navigator.sendBeacon for reporting the errors to the server.

I intend to work on this soon unless someone else volunteers. When that happens I'll update the assignee to myself and remove "good first bug". In the meantime, community members should feel free to use the comments to submit small examples that illustrate good production uses of these events.