[sullyj3]

I'd say it depends heavily on what you're writing. If it involves graphics, Javascript is going to be substantially less annoying, at least initially. However, the version you write in Haskell will be much more reliable, and much easier to progressively refactor and scale up, whereas in JS, the weird edge cases and lack of static guarantees will gradually pile up and make the project a chore to maintain.

For something non graphics related that you're building by yourself, if you already know Haskell, it's a no brainer, due to the high expressivity ceiling. Once a team is involved, the right choice (as always) basically just depends on what people already know.