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1+# Frequently Asked Questions
2+
3+### How do I configure DOM events with flags like `preventDefault` and `stopPropagation`?
4+
5+Using `element`, a low-level DOM builder function. Its second argument, `ElementConfig`, has a `_elementConfig_eventSpec` field that can be modified using `addEventSpecFlags`. It takes a `Proxy` that specifies the `DomSpace`, an event name, and a callback which takes the event result and returns an event flag, which can enable behavior like `preventDefault` and `stopPropagation`.
6+
7+The type signature on `def` is needed because the fields of the `ElementConfig` can change the type of the `ElementConfig`. GHC can probably figure out the type of the resulting `ElementConfig`, but it doesn't know what the type of `def` was before the modifications, since it never gets used with that configuration.
8+
9+For example:
10+
11+```haskell
12+{-# LANGUAGE OverloadedStrings #-}
13+{-# LANGUAGE ScopedTypeVariables #-}
14+
15+import Control.Lens ((&), (%~), (.~))
16+import Data.Proxy
17+import Reflex.Dom
18+
19+main :: IO ()
20+main = mainWidget $ do
21+ (click, ()) <- linkPreventDefault $ text "reflex-frp"
22+ display =<< count click
23+
24+linkPreventDefault :: forall t m a. DomBuilder t m => m a -> m (Event t (), a)
25+linkPreventDefault c = do
26+ let cfg = (def :: ElementConfig EventResult t (DomBuilderSpace m))
27+ & elementConfig_initialAttributes .~ ("href" =: "https://reflex-frp.org")
28+ & elementConfig_eventSpec %~ addEventSpecFlags (Proxy :: Proxy (DomBuilderSpace m)) Click (const preventDefault)
29+ (link, a) <- element "a" cfg c
30+ return (domEvent Click link, a)
31+```