If any function definition occurs in the script, we get

Running...
Aborted(undefined)
Error: Aborted(undefined). Build with -sASSERTIONS for more info.

From:

https://chaiscript.com/playground.html

With no debugging info to be had.

Investigate here: ChaiScript/ChaiScript#662
and: https://github.com/RobLoach/ChaiScript.js

to see what might be up. The RobLoach site works fine. It even gracefully handles exceptions being thrown.