[ck2]

I think it's more of an (impressive) mental exercise - if the code can be made straightforward enough to run on javascript, the future applications can only grow from there.

[robert-boehnke]

It's the Android encoder written in c++ cross compiled to JavaScript, not much of a mental exercise. Not to say it's not cool :)

[ZeroGravitas]

They have a hand-coded javascript version in progress too:

https://github.com/mbebenita/Broadway/tree/master/Play