IconVault's JS Error Trace makes exception propagation visible. Write or pick a scenario, run it in a sandboxed iframe, and the tool catches the real error, parses its stack trace, and animates each frame being pushed, the throw, and the unwind until a catch handles it or it escapes uncaught.

Scenarios cover the classics: nested throws, uncaught errors, catch and rethrow, the async boundary where setTimeout loses the stack, and unhandled promise rejections. Everything is free and runs fully in your browser, with your code isolated from the page.