Add file ParseJS.hs for review.

This is the first layer in the pipeline. It turns the parse tree (output from hackage.haskell.org/package/language-javascript-0.4.5) into a more useful AST.

PTAL.
You can use listToMaybe (from Data.Maybe) to convert '[a] -> Maybe a'
Maybe is a monad, so you can liftM an 'a -> b' to produce a 'Maybe a -> Maybe b'.

hence jsnToMaybeListExp could be written as 
jsnToMaybeListExp = liftM jsnToListExp . listToMaybe