ghcjs-commonjs

ghcjs-commonjs is a work-in-progress collection of little hacks to make GHCJS and CommonJS integration less troublesome.

By that we mean:

• Easy implementation of calling Haskell code from JavaScript code
• Easy implementation of calling JavaScript code from Haskell

The first point is where the most friction is, since the GHCJS FFI is pretty stellar.

We provide the following tools:

• ghcjs-require - Calling Haskell from Node.js and CommonJS
• ghcjs-register - require('./MyHaskellModule.hs')
• ghcjs-loader - A webpack loader for GHCJS

ghcjs-require

Utilities for loading GHCJS .jsexes from CommonJS land.

Callling Haskell from JavaScript

This is main.js:

const ghcjsRequire = require('ghcjs-require');
const Main = ghcjsRequire('./Main.jsexe');
// ^^ This is a function that boots the Haskell RTS
Main(({wrapped}) => { // <- This callback is executed after the RTS is loaded
  wrapped.someFunction().then(() => console.log('someFunction is over'));
  // ^^ This function was generated, it'll call Haskell code asynchronously and
  //    return a promise to the result (the result needs to be a JavaScript
  //    value)
});

This is Main.jsexe:

import Control.Concurrency (threadDelay)
import GHCJS.CommonJS (defaultMain, export)
someFunction = do
    putStrLn "Waiting for a second"
    threadDelay (1000 * 1000)
    putStrLn "Done!"
main =
    exportMain [("someFunction", someFunction)]

ghcjs-register

On the likes of coffee-script/register or babel-register:

require('ghcjs-register');
const Main = require('./Main.hs');

ghcjs-loader

This is a webpack loader for GHCJS. See the examples.