Elm:
Envoi d'une requête HTTP

import Http
import Json.Decode as Decode

type alias User =
    { id : Int
    , name : String
    }

userDecoder : Decode.Decoder User
userDecoder =
    Decode.map2 User
        (Decode.field "id" Decode.int)
        (Decode.field "name" Decode.string)

fetchUser : Int -> Cmd Msg
fetchUser userId =
    Http.get
        { url = "https://api.example.com/users/" ++ String.fromInt(userId)
        , decoder = userDecoder
        }
        |> Http.send UserFetched

type Msg
    = UserFetched (Result Http.Error User)

update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
    case msg of
        UserFetched (Ok user) ->
            ({ model | user = Just user }, Cmd.none)

        UserFetched (Err _) ->
            (model, Cmd.none)