npm install --save redux-rereducers

import { createStore } from 'redux'
import { applyHigherOrders } from 'redux-higher-orders'
import { createRereducerHigherOrder } from 'redux-rereducers'
 
const rereducers = [
  (state) => {
    ...state
  },
  rereducer2,
  rereducerN
]
 
let store = createStore(
  reducer,
  initialState,
  applyHigherOrders(
    createRereducerHigherOrder(rereducers)
  )
)

import { createStore } from 'redux'
import { handleActions } from 'redux-actions'
import { applyHigherOrders } from 'redux-higher-orders'
import { createRereducerHigherOrder } from 'redux-rereducers'
 
const reducer = handleActions({
  INCREMENT: (state, action) => ({
    counters: {
      ...state.counters,
      [action.payload]: state.counters[action.payload] + 1
    }
  }),
 
  DECREMENT: (state, action) => ({
    counters: {
      ...state.counters,
      [action.payload]: state.counters[action.payload] - 1
    }
  })
}, { counters: {}, average: 0 })
 
 
const rereducer = (state) => ({
  ...state,
  average: calculateAverage(state.counters)
})
 
const store = createStore(
  reducer,
  initialState,
  applyHigherOrders(
    createRereducerHigherOrder([rereducer])
  )
)
 
store.dispatch({
  type: 'INCREMENT',
  payload: 'a'
})
 
store.dispatch({
  type: 'INCREMENT',
  payload: 'b'
})
 
store.getState()  // { counters: { a: 1, b: 1 }, average: 1 }