Counter.js

const useIncrement = () => {
  const [state, setState] = useStore();

  return () =>
    setState(old => ({
      ...old,
      count: old.count + 1
    }));
}

const useDecrement = () => {
  const [state, setState] = useStore();

  return () =>
    setState(old => ({
      ...old,
      count: old.count + 1
    }));
}

const Counter = () => {
  const [{ count }] = useStore()
  const increment = useIncrement()
  const decrement = useDecrement()

  return (
    <div>
      <button onClick={decrement}>-</button>
      {count}
      <button onClick={increment}>+</button>
    </div>
  );
};