Have you tried livescript(http://livescript.net/) or clojurescript(https://github.com/emezeske/clojurescript)? I know that they don't have all of Haskell's features but they do bring Javascript a little bit closer to languages like Haskell.

This is a good example of the ways clojurescript improves on javascript: http://himera.herokuapp.com/synonym.html

I do not particularly care about having a pretty syntax, what I want is the high assurance that the program will not be wrong.

Have you tried using haste or fay? (I haven't, just curious)

Who said it was amazing?