AFAIK the OP is the head behing the debugger of firefox devtools. Will this work be useful for the debugger or somehow enhance it? Just curious as I do not see the 'practical' merits of this work.

Don't get me wrong, learning stuff and hacking by itself is always interesting – I'd just like to know if there is something in for me as a user of the firefox JS debugger.

Very cool! I'm wondering if it will work on Nashorn. I actually have a need to be able to debug JavaScript code running inside Nashorn without touching the JVM debugger.

very cool..!