Emscripten is an LLVM-based project that compiles C and C++ into asmJS

Emscripten is an LLVM-to-JavaScript compiler. It takes LLVM bitcode – which can be generated from C/C++, using llvm-gcc (DragonEgg) or clang, or any other language that can be converted into LLVM – and compiles that into JavaScript, which can be run on the web (or anywhere else JavaScript can run).