C++ is already used in production by big companies. It currently is deployed as asm.js. But you can use an equivalent toolchain to create WebAssembly. This way

C++ is already used in production by big companies. It currently is deployed as asm.js. But you can use an equivalent toolchain to create WebAssembly. This way you can create production-ready code and be ready to move to WebAssembly as soon as it gets feature ready. The fine control that C++ offers will help you to understand the underlying architecture and put its performance to test.