minimal version of redux createStore

createStore.js

export const createStore = (reducer, preloadedState, enhancer) => {
  if (enhancer) return enhancer(createStore)(reducer, preloadedState);

  const listeners = new Set();
  let state = reducer(preloadedState, { type: `INIT:${performance.now()}` });

  return {
    dispatch: action => void (state = reducer(state, action), listeners.forEach(fn => fn())),
    subscribe: listener => (listeners.add(listener), () => listeners.delete(listener)),
    getState: () => state,
  };
};