GHCJS vs Fay

With a Haskell backend, GHCJS enables code sharing. In combination with the power of Haskell as a language, this enables an extremely tight integration of the client side with the server side, where all the communications take place in a type-safe manner and even transparently if desired.

No need to learn new syntax or semantics, and no need to install and learn a bunch of new tools - it's just GHC.

Haskell is a very terse language, particularly due to its type inference. This means there's nothing to distract from the intent of the code, making it very readable. This is in sharp contrast to languages like Java, where skimming code requires learning which details can be ignored. Haskell's terseness also lends itself to very clear inline examples in textbooks, and makes it a pleasure to read through code even on a cellphone screen.

It's often said that, in Haskell, if it compiles, it works. This short feedback loop can speed up learning process, by making it clear exactly when and where mistakes are made.

Fay produces smaller output than pure Haskell compilers such as GHCJS; It does not need to include the whole Haskell runtime, as it drops support for features such as multi-threading, giving it fewer dependencies.

As with UHC, the FFI to Javascript works with printf-style format:

max = ffi "Math.round(%1,%2)"

This can simplify code needed to make calls to methods on objects, in contrast to e.g., Purescript's FFI, which requires that methods be wrapped in Javascript. Similarly to UHC, Fay also supports the use of %*, for javascript functions with arbitrary numbers of parameters, such as concat, though they must expose an explicit number of parameters to Fay.

Fay is available on Cabal, as are Fay packages, so getting up and running is as simple as typing 'cabal install'. Happstack, Snap, and Yesod packages are available on Hackage, as are bindings for JQuery and Backbone.

Since Fay is a subset of Haskell - Lazy, statically typed, and pure by default. There's no new syntax to learn, and no surprises when it comes to the semantics of your code. This extends into function names as well - Fay programmers can use familiar functions such as putStrLn to output to the console, rather than Javascript-specific versions.