Do note, that some functional languages have good out-of-the-box support for both backend and frontend. An this is not negligible. I'm using F# which in combina

Do note, that some functional languages have good out-of-the-box support for both backend and frontend. An this is not negligible. I'm using F# which in combination with Fable (F#->.js transpiler) lets me really quickly share code, datastructures and serialization with frontend code. Now, I'm a primarily a backend developer. But sometimes it is just really convenient to be able to hack together an in-house real-time data-analysis or reporting service and render statistics as webpages rather than .csv documents. If your frontend team is functional as well, then the benefits of sharing the language could be even bigger. Sure, not everything is perfect in the F# world. However having the possibility to share code with frontend saves me more time than I spend in fighting with the F# ecosystem. And also: programming in F# is just fun joyful. And productive.