PureScript is a strongly, statically typed language which compiles to JavaScript. It is written in and inspired by Haskell and aims at "allowing to write very expressive code which is still clear ...

Coders choose programming languages for any number of technical reasons, but they also choose them for very personal reasons—and these personal reasons inevitably intertwine with the technical.

Haskell is a 25-year-old programming language that isn't all that popular. But Facebook uses it, and that's a sign of things to come.