Any sort of compiler for JavaScript could only support a subset of the language, unless you shipped an interpreter alongside the compiled code. This subset might be unfamiliar enough to the point that moving to a new language wouldn't be that much harder for some programmers.
I also see nothing on the site to suggest that C/C++ (at least) couldn't be supported, although I have no clue how much work you would have to do yourself (likely too much).
I also see nothing on the site to suggest that C/C++ (at least) couldn't be supported, although I have no clue how much work you would have to do yourself (likely too much).