If you want your C++ code to run on the web, there is Emscripten, but there is also Cheerp:

Cheerp 1.1 - C++ for the Web with fast startup times, dynamic memory and now, more speed!

by Leaning Technologies Ltd.

From the article:

Cheerp is a C++ compiler for the Web platform. Roughly a year ago we released Cheerp 1.0 with the promise of making C++ a first class language for the Web, with full access to DOM and HTML5 APIs (including WebGL) and great performance. At that time, we could only partially meet that promise.

With our early adopters starting to use Cheerp on real world, large scale applications, we were proud to see that Cheerp could indeed be used to seamlessly integrate C++ code into HTML5 apps. But we also realized that the performance of the compiled code was disappointing on real codebases.

As an example, our first benchmarking result on our first large-scale (~1M sloc) customer code was around forty times (40x) slower than native. Not only was this result disappointing, but it also was much worse than what we were expecting based on our internal benchmarks.

One year later, after significant effort focused on performance optimizations, we are here today to announce Cheerp 1.1...