Node main for Server-side Elm

Node main for Server-side Elm programs

Install

There's no installation necessary, this is a boilerplate file that can be used as the entry point for all Server-side or command line based Elm programs.

Usage

Your final output of your Elm build must be called elm.js. This will be loaded via require in main.js:

elm make YourApp.elm --output elm.js

Then your main Elm App should be a port module:

port module YourApp exposing (..)

Then your Elm code can initiate a controlled shutdown by writing the exit code to a port called node:

port exitApp : Float -> Cmd msg

When it's time to exit, your update function can do the following:

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    case msg of
		SomeEvent ->
			(model, exitApp 1)

See YourApp.elm code for more usage details.

SIGINT and SIGTERM

These OS signals will send a message to your program. In the case of the test app, YourApp.elm, an Abort message is sent. Then the exitApp Cmd is returned from update with a parameter of -1 which will be returned to the OS.

This approach allows your Elm code to shutdown cleanly and allows you Elm code to always be in control.

Exit Handlers

Besides the Elm exit handler, it also has a handler for Unhandled Exceptions which returns 1 to the OS. This is useful if you've written or used any badly behaved Javascript code.