The main use for it (for me at least) is to write fast numerical code (physics modeling, audio processing, image processing, machine learning, 3D rendering, statistical analysis, etc.) in a deterministically fast way against an easy-to-reason-about programming model with an ability to manually allocate memory and structure data, instead of hoping that every browser’s heuristic-driven JIT will be able to optimize some high-level code the same way.<p>Most of the program logic can remain standard Javascript, but the little kernels of hot numerical code can be much more effectively optimized.<p>This gives Javascript&#x2F;browsers the ability to handle problems which were previously only possible to tackle with native C programs.