const reactInit = '@@react/Init'

const combineReducers  = (reducers) => {
       const finalReducers = {}     for (let key in reducers) {
           const reducer = reducers[key]         if (typeof reducer === 'undefined') {
               console.error(`reducer${key}的值是undefined`)         }         if (typeof reducer === 'function') {
               finalReducers[key] = reducer         }     }     for (let key in  finalReducers) {
           const reducer = finalReducers[key]         const state = reducer(undefined, reactInit)         if (typeof state === 'undefined'){
               throw new Error(`reducer${key}的返回值为undefined`)         }     }     return (state={}, action) => {
           for (let key in finalReducers) {
               const reducer = finalReducers[key]             const newState = reducer(state[key], action)             state[key] = newState         }         return state     } }