The Church-Turing thesis says that problems solvable by a UTM are also solvable by lambda-calculus. So yes, any problem that can be solved in javascript can also be solved in haskell.
Would you answer him the same way in person if he came to a Haskell meetup?
What the GHC runtime does is somewhat comparable to what Node.js does.
...time to get to work on that framework...