store.js

import { useState, useEffect } from 'react'

const store = {
  state: {},
  setters: []
};

export function setStore(value) {
  store.state = value;
  store.setters.forEach(setter => setter(store.state));
}

export function useStore() {
  const [ state, set ] = useState(store.state);
  if (!store.setters.includes(set)) {
    store.setters.push(set);
  }

  useEffect(() => () => {
    store.setters = store.setters.filter(setter => setter !== set)
  }, [])

  return [ state, setStore ];
}