pcl.js is a Point Cloud Library (PCL) that runs in the browser, powered by Emscripten and WebAssembly. Point Cloud Library (PCL) is a standalone, large scale, open C++ project for 2D/3D image and point cloud processing.
What is your point here? This is a point cloud library compiled to webassembly. All you seem to be saying is that browsers and compilers are written in C++, which doesn't really have anything to do with this.
Github: https://github.com/luoxuhai/pcl.js