如何实现一个redux?

const createStore = function (reducer, initState) {
  let state = initState;
  let listeners = [];

  function subscribe(listener) {
    listeners.push(listener);
  }

  function dispatch(action) {
    const currentState = reducer(state, action);
    state = currentState;
    listeners.forEach((handler) => handler());
  }
  function getState() {
    return state;
  }
  return { subscribe, dispatch, getState };
};

const combineReducers = (reducers) => {
  const keys = Object.keys(reducers);

  return function (state = {}, action) {
    const newState = {};
    keys.forEach((key) => {
      const reducer = reducers[key];
      const next = reducer(state[key], action);
      newState[key] = next;
    });
    return newState;
  };
};