useApp.js

const useApp = () => {
  const [state, dispatch] = useReducer(reducer, initialState)
  
  const onSubmit = (friend, resetValues) => (e) => {
    e.preventDefault()
    if (!friend.name) return
    dispatch({ type: 'add-friend', friend })
    resetValues()
  }
  
  const undo = () => {
    dispatch({ type: 'undo' })
  }
  
  return {
    ...state,
    onSubmit,
    undo,
  }
}