Every Emscripten demo I've seen so far has either not worked, or been horribly slow. As far as I'm concerned, it really isn't a viable option at this point for anything remotely serious. It may be an interesting experimental idea, but it still needs a massive amount of work before it's seriously usable.
In the end, they're merely an abuse of JavaScript, rather than providing proper support like NDK provides for C and C++ under Android, for instance.
Asm.js is still just JavaScript. Emscripten isn't currently production-grade software, and it still just compiles down to JavaScript.
I hope you understand that either of those options is still a case of using JavaScript. Are you seriously disputing that?
We can develop production-grade applications using Java, C, C++, C# and JavaScript for Android. We can only do a very small fraction of that when using Firefox OS. Firefox OS clearly provides far fewer viable options than Android does.
Every Emscripten demo I've seen so far has either not worked, or been horribly slow. As far as I'm concerned, it really isn't a viable option at this point for anything remotely serious. It may be an interesting experimental idea, but it still needs a massive amount of work before it's seriously usable.
In the end, they're merely an abuse of JavaScript, rather than providing proper support like NDK provides for C and C++ under Android, for instance.