F# on .NET Core is my favorite right now by a fair margin. It runs anywhere, is extremely fast, and jetBrains Rider is great. The .NET ecosystem has a library f

F# on .NET Core is my favorite right now by a fair margin. It runs anywhere, is extremely fast, and jetBrains Rider is great. The .NET ecosystem has a library for everything, and comes with a lot of batteries included. F# is a great compromise between purely functional and pragmatic. If not F#, then Haskell comes in second, and Clojure comes in third. For a web frontend, if it can't be server side rendered templates, then React and Typescript.