There are several strongly typed (and functional) languages being built for the web that compile to JavaScript:

   ReasonML - OCaml - https://reasonml.github.io
   PureScript - Haskell - http://www.purescript.org
   TypeScript - https://www.typescriptlang.org
   Scala.js - http://scala-js.org
   Elm - https://elm-lang.org
   ghcjs - Haskell (https://github.com/ghcjs/ghcjs)

This podcast covers many of them:

http://bikeshed.fm/192