An advancement in the world of C++ to javascript:

Cheerp PreExecuter: compile-time evaluation of constructors

by Sander Mathijs van Veen

From the article:

The size of a JavaScript web application, especially when compiled from a complex C++ source, has a key role on the quality of the user experience, being directly connected to the download and startup time. Size also has a big impact on the traffic and bandwidth needs of the hosting server, which translates one to one into costs. Therefore, minimizing the size of JavaScript applications compiled from C++ with Cheerp has always been one of our priorities...