import React, { useContext } from 'react';
import { createContextIO } from 'react-context-io';

const CountStore = createContextIO(0);

const Result = () => {
  const count = useContext(CountStore);
  return <div>{count}</div>;
};

const AddButton = () => (
  <button onClick={() => CountStore.write(count => count + 1)}>+</button>
);

const Counter = () => (
  <CountStore.Provider>
    <Result />
    <AddButton />
  </CountStore.Provider>
);