Speaking of python things, there's an actively developed JavaScript implementation of tensorflow called tensorflow.js, which has its own set of backends to leverage GPUs in browsers or in node.js though webGL, webgpu or node bindings into c++ stuff to get cuda support, alongside wasm and pure js implementations.
I've used it! My gripe is that I'm not fond of their async implementations, it blows up the code when I want to do something simple. I understand the tradeoff is there in order to utilize external hardware for bigger tensor applications, but sometimes I just want a thin API for n-dimensional operations... like ... well, you know what I'm going to say. :)
And every time I see it, I cry that JavaScript doesn't have something like numpy.
numpy is just so damn logical and fast (and comprehensive!) that i don't consider myself a python programmer, i'm a numpy user.
EDIT: (removed complaint). That said: this looks like a good foundation for someone to use for implementing a fully featured numpy in JS.