Some Elm Code

Main.elm

module Main exposing (..)

import Browser
import Html exposing (text, div, button, Html)
import Html.Events exposing (onClick)
import Http exposing (get)
import Image exposing (Image)

type alias Model = String

type Msg = ButtonClicked | MsgReceived (Result Http.Error String)

type MyCmd = FetchSelf | NoOperation

pageUrl =
  "http://localhost:8000"

getPage = get {url= pageUrl, expect= Http.expectString MsgReceived }


update : Msg -> Model -> (Model, MyCmd)
update msg model = case msg of
  ButtonClicked -> ( "Look!", FetchSelf )
  MsgReceived result -> 
      case result of 
        Err _ -> ("Could not retrieve", NoOperation)
        Ok content -> (content, NoOperation)


convert : (model, MyCmd) -> (model, Cmd Msg)
convert cmd = 
  case cmd of
    (model, FetchSelf) -> (model, getPage)
    (model, NoOperation) -> (model, Cmd.none)

view : Model -> Html Msg
view model =
  div []
      [text model, button [onClick ButtonClicked] [text "le bouton"]]

main : Program () Model Msg
main = Browser.element
    { init = \_ -> ( "Hello", Cmd.none )
    , view = view
    , update = \msg model -> update msg model |> convert
    , subscriptions = \_ -> Sub.none
    }