I'm currently writing a tutorial on web applications using Haskell. I know the pros and cons of each server-side library (Yesod, Snap, Scotty, Warp, Happstack), but I'm looking for the right choice for client-side programming that converts Haskell to JavaScript. I've finally come to Fay vs. GHCJS, and would like your opinion on what's the best to tackle. My current list of pros and cons is:

Fay

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Pros:

- Does not need GHC 7.8

- Easy FFI with JS

- Has libraries for integration with Yesod and Snap

Cons:

- Only supports a subset of GHC (in particular, no type classes)

GHCJS

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Pros:

- Supports full GHC

- Easy FFI with JS

- Highly opinionated point: will stay longer than Fay (but it's very important for not having a tutorial that is old in few months)

Cons:

- Needs GHC 7.8 (but provides a Vagrant image)