This is a short example of what features the native extension brings for the HTML5 platform
C/C++ - Add pure C/C++ code or C/C++ libraries built with Emscripten
EM_ASM - Add "in place" JavaScript code directly in your C/C++ code
JavaScript libraries - Add Emscripten JavaScript libraries. These are JavaScript files with special "hooks" that the Emscripten compiler will react to and merge with the final executable
Emscripten is a Clang based compiler that allows for compiling existing C/C++ code into JavaScript and WebAssembly.
The example app demonstrates these features, and also shows an example of how to pass information to the running game.