Node Elm Loader

A simple way to interoperate between Elm and NodeJS. Useful for sharing code between display and model logic, which holding it together with the rich Node ecosystem, for example, building your client-side components and minifying them with the rest of your assets!

Installation

You will need to already have the Elm platform installed on your system. Please find the relevant instructions here and a NodeJS development environment for v0.12.x. It is now also possible to install Elm with npm install -g elm if you prefer.

Then, simply add elm-loader as a dependency in your package.json or run npm -g elm-loader.

Usage

First, write a simple module in Elm and expose a port! Due to a current bug in the compiler, you need to supply a dummy main function. Once this is resolved, it will be possible to proceed without the boilerplate.

module TickingPort where

import Signal
import Signal ((<~), Signal)

import Time

import Text
import Graphics.Element (Element)
main : Element
main = Text.asText "main"

port messageOut : Signal String
port messageOut = Signal.map toString (Time.every Time.second)

Next, wire import your module into Node!

var path = require("path");
var Elm = require("elm-loader");

var compiledCode = Elm(path.resolve(__dirname, "ticking_port.elm"), __dirname);

compiledCode.emitter.on("messageOut", function(message) {
  console.log(message)
});

Watch it tick!

$ node test.js
1418683956865
1418683957870
1418683958873
1418683959874
1418683960875
^C

You can also access the ports property, rather than the emitter on the object returned by the top level factory function and subscribe as you would with a typical setup.

Caveats

The loader supports conventional CamelCase filenames for the Elm modules they contain. If you prefer to split thw words in your filenames with underscores, they will automatically be inflected to infer the module they contain, e.g. ticking_port.elm will correspond to the TickingPort module above.

If you are defining ports into Elm, you also need to supply a second argument to the factory function to define the defaults for those functions, e.g.

var echoPort = Elm(path.resolve(__dirname, "fixtures/echo_port.elm"), "fixtures", {
  messageIn: ""
});

Example

To try it out, clone this repository, run npm link and then run node example/test.js!