Duetto is an alternative open-source project to EmScripten, the LLVM-based project for compiling C/C++ code-bases into JavaScript for execution by modern HTML5 web-browsers. Duetto is still LLVM-based and relies on JavaScript, but there's a few changes over EmScripten.

Duetto has been in development for some months by Learning Technologies Ltd. Duetto is similar to EmScripten in that it uses LLVM for converting C++ code into JavaScript. However, Duetto is able to convert C++ OOP programming into native JavaScript objects and Learning Technolgies also claims other speed improvements over EmScripten on Firefox and Chrome.

A developer for the company has now shared that Duetto now has a fully working libc and libc++ implementation for a standard C and C++ library, CMake/Autotool support has been integrated, and there's now full support of the DOM and HTML5 APIs. This does include use of WebGL from C++. The company has also made a small WebGL demo that utilizes the Bullet physics library.

More details on the Duetto project can be found in this blog post. The company plans to release Duetto as open-source for non-commercial use while a commercial product will also be available in the coming months.