Test.elm

module Test exposing (..)

import Html exposing (..)
import Html.App as App
import Html.Attributes exposing (..)
import Html.Events exposing (..)

import List exposing (map)
import Json.Decode as Json

type alias Model =
    Maybe String

init = Nothing

type Msg
    = Switch String

update (Switch s) model =
    Debug.log"" <| Just s

view model =
    let
        kvs =
            [ ("1", "One")
            , ("2", "Two")
            ]
        makeOpts lst selectedKey =
            lst
            |> map (\(k, v) ->
                option
                    [ value k
                    , selected <| k == selectedKey
                    ] [ text v ])
    in
    select
        [ onInput Switch ] <|
        case model of
            Just s ->
                makeOpts kvs s
            Nothing ->
                makeOpts
                    (("0", "Zero") :: kvs)
                    "0"

main = App.beginnerProgram
    { model = init
    , view = view
    , update = update
    }

onChange : (String -> a) -> Attribute a
onChange messageCreator =
    on "change" (Json.map messageCreator targetValue)

Using Html.Keyed solves this:

module Test exposing (..)

import Html exposing (..)
import Html.App as App
import Html.Attributes exposing (..)
import Html.Events exposing (..)
import List exposing (map)
import Json.Decode as Json
import Html.Keyed


type alias Model =
    Maybe String


init =
    Nothing


type Msg
    = Switch String


update (Switch s) model =
    Debug.log "" <| Just s


keyedSelect =
    Html.Keyed.node "select"


view model =
    let
        kvs =
            [ ( "1", "One" )
            , ( "2", "Two" )
            , ( "3", "Three" )
            ]

        makeOpts lst selectedKey =
            lst
                |> map
                    (\( k, v ) ->
                        ( k
                        , option
                            [ value k
                            , selected <| k == selectedKey
                            ]
                            [ text v ]
                        )
                    )
    in
        keyedSelect [ onInput Switch ]
            (case model of
                Just s ->
                    makeOpts kvs s

                Nothing ->
                    makeOpts (( "0", "Zero" ) :: kvs)
                        "0"
            )


main =
    App.beginnerProgram
        { model = init
        , view = view
        , update = update
        }


onChange : (String -> a) -> Attribute a
onChange messageCreator =
    on "change" (Json.map messageCreator targetValue)