How to determine which setWatch callback function triggers the E.getErrorFlags() CALLBACK error

Thr 2020.04.02

Thank you for that confirmation Gordon. While I had substituted a conditional test along with 'throw'ing my own formatted error, I wanted to make sure from a message bubble up procedure standpoint, that the assert feature didn't already exist.

Note to those overriding as in the example above, that the procedural handling will be slightly different than what MDN explains at the link in #6 post above.

EDIT:   Sun 2020.04.19
Found a method to capture unhandled exceptions:
http://www.espruino.com/Reference#l_proc­ess_uncaughtException