redux createstore

createstore.js

// basic instance of store in redux
const createStore = reducer => {
  let state;
  let listeners = [];

  const getState = () => state;

  const dispatch = action => {
    state = reducer(state, action);
    listeners.forEach(listener => listener());
  };

  const subscribe = listener => {
    listeners.push(listener);
    return () => {
      listeners = listeners.filter(l => l !== listener);
    };
  };

  dispatch({});

  return { getState, dispatch, subscribe };
};