elm-node-backend

Minimal Elm backend on Node.js. Elm handles routing via ports; Node handles HTTP.

Run

npm ci
npm start

How it works

HTTP Request → Node → port request → Elm → port response → Node → HTTP Response

The Node.js response object is passed through Elm as an opaque Decode.Value, eliminating the need for request tracking or ID correlation. When Elm processes a request, it returns the same opaque response object, allowing Node to write directly to the correct HTTP response.

Project structure

src/
├── Main.elm    -- Program wiring (ports, subscriptions) - don't touch
├── Api.elm     -- Stable types and JSON encoding - don't touch
└── Routes.elm  -- Your routes and handlers - edit this!

Only Routes.elm needs editing. Add routes by extending the case expression and writing handlers:

route : Request -> Response
route req =
    case ( req.method, req.path ) of
        ( Get, "/" ) ->
            homeHandler req

        ( Get, "/hello" ) ->
            helloHandler req

        ( Post, "/echo" ) ->
            echoHandler req

        -- Add new routes here

        _ ->
            notFoundHandler req