Function useCount

packages/react-reconciler/src/__tests__/useEffectEvent-test.js:488–495

(incrementBy)

    }

    function useCount(incrementBy) {
      const [count, updateCount] = useState(0);
      const increment = useEffectEvent(amount =>
        updateCount(c => c + (amount || incrementBy)),
      );

      return [count, increment];
    }

    function Counter({incrementBy}) {
      const [count, increment] = useCount(incrementBy);