Stop propagation thing

Foo.hs

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
import Control.Lens hiding (element)
import Control.Monad.IO.Class
import Data.Map (Map)
import Data.Monoid
import Data.Proxy
import Data.Text (Text)
import Reflex.Dom

main :: IO ()
main = mainWidget app

app :: forall t m. MonadWidget t m => m ()
app = do
  (e, submit) <- elDynAttrWithModifyConfig'
    (\elCfg -> elCfg & elementConfig_eventSpec %~
      addEventSpecFlags (Proxy :: Proxy (DomBuilderSpace m)) Submit (\_ -> preventDefault))
    "form"
    (pure mempty)
    (button "SUBMIT")
  performEvent_ $ ffor submit $ \_ ->
    liftIO $ putStrLn "SUBMIT WAS CLICKED"
  return ()

elDynAttrWithModifyConfig'
  :: (DomBuilder t m, PostBuild t m)
  => (ElementConfig EventResult t (DomBuilderSpace m) -> ElementConfig EventResult t (DomBuilderSpace m))
  -> Text
  -> Dynamic t (Map Text Text)
  -> m a
  -> m (Element EventResult (DomBuilderSpace m) t, a)
elDynAttrWithModifyConfig' f elementTag attrs child = do
  modifyAttrs <- dynamicAttributesToModifyAttributes attrs
  let cfg = def & modifyAttributes .~ fmapCheap mapKeysToAttributeName modifyAttrs
  result <- element elementTag (f cfg) child
  postBuild <- getPostBuild
  notReadyUntil postBuild
  return result