Functional 'concepts' are not niche, but functional languages still are. If you asked your average Java 8 programmer or JS programmer to write an app in Haskell or Elm, they'd struggle.

I'd consider myself an average JS programmer and would love to try writing web apps in Haskell. I've spent some time on Haskell books, fell in love with the type system, got a basic understanding of monads but found it difficult to "move forward".

I think the issue for me is I predominantly build web apps. Can you recommend any resources for building modern web apps in Haskell or at least fitting it into my day to day at work?

Try PureScript! [1]

Haskell-like (but taking away some of the pain points), for the frontend, compiles to very readable javascript.

[1]: http://www.purescript.org/

That looks really cool :) does it still depend on Bower?

There's no "dependency" per se, but in practice most of the community still uses bower.

There's an effort to make something better and on the same vibe as Haskell's `stack`, which is `psc-package` [1].

I switched to it for all new projects, and while it still has some rough edges, I don't really miss bower.

[1]: https://github.com/purescript/psc-package

Unfortunately, does not use persistent data structures.

Yes it does.

So did C++. But you can't program C++ or Java in a functional manner the way you can an actual FP language. Largely due to lack of proper data structures for FP.