Many things that emerged at Facebook during recent years can be attributed to the influence of Haskell. React, Immutable.js, GraphQL, etc. Haskell is extremely powerful but allow me to rephrase Euclid "There's no royal road to functional programming". If you want something more pragmatic, yet still quite expressive and powerful - try Clojure and Clojurescript. Especially Clojurescript - it's probably one of the best languages out there to use for front-end and mobile app development.