No doubt you're right, but I don't think JS is well suited for scientific computing. At least Python gives you operator overloading. Julia and R are designed for this field. It's better for JS to remain on the presentation side for anything sophisticated.
Forgive me if I read the response wrong but that seems like exactly what the author is saying? Do your computing in Python/R, export a generated CSV, and then present it in Observable?
With the possibility that WebAssembly and WebGL will make the libraries in Python/R available to JS. Which might be alright. You probably won't be able to utilize vectorization with operators.
