You should check out runtime.js [1] if you haven't. Instead of duktape it uses v8. I'd like to see an equivalent project using spider monkey so that C/C++ code could be compiled into efficient JS. Check out this speech if you haven't already: The Birth & Death of JavaScript [2]

[1] https://github.com/runtimejs/runtime [2] https://www.destroyallsoftware.com/talks/the-birth-and-death...