Fay

Fay has the following properties:

A proper syntactic and semantic subset of Haskell
Statically typed
Lazy
Pure by default
Compiles to JavaScript
Has fundamental data types (Double, String, etc.) based upon what JS can support, and compound data types (ADTs and GADTs)
Outputs minifier-aware code for small compressed size
Has a trivial foreign function interface to JavaScript
Supports cabal installation of Fay packages
Can automatically transcode values to/from JSON using the FFI
Provides an API to transcode on the server side as well
Lets you call Fay code from JavaScript
Has the Fay monad for side effects (think of it like IO)

Install:

cabal install cpphs 
# make sure cpphs is in your PATH
cabal install fay fay-base

Write awesome software:

{-# LANGUAGE EmptyDataDecls #-}
module Hello where

import FFI

data Event

alert :: String -> Fay ()
alert = ffi "alert(%1)"

setBodyHtml :: String -> Fay ()
setBodyHtml = ffi "document.body.innerHTML = %1"

addWindowEvent :: String -> (Event -> Fay ()) -> Fay ()
addWindowEvent = ffi "window.addEventListener(%1, %2)"

greet :: Event -> Fay ()
greet event = do
  putStrLn "The document has loaded"
  setBodyHtml "Hello HTML!"

main :: Fay ()
main = do
  putStrLn "Hello Console!"
  alert "Hello Alert!"
  addWindowEvent "load" greet

Compile it: fay Hello.hs --html-wrapper

Run the generated Hello.html

Tags: language functional nodejs browser

Last modified 01 July 2021

Fay

A proper subset of Haskell that compiles to JavaScript.