NaCl/Emscripten

[via Digitalmars-d]

There are also other compilers from C++ to Javascript, Mandreel 
and Cheerp.

Cheerp claims to support the builtin Javascript garbage collector:

«Dynamic memory management. C++ objects are translated directly 
to JS objects, without the proxy of an emulated, flat memory 
space. Allow your applications to exploit the JavaScript VM 
garbage collector and co-exist with fair, on-demand memory 
allocation.»

http://www.leaningtech.com/cheerp/blog/

So if Cheerp is ready for production (I don't know if it is), it 
might be a better fit for D.