ReducerChain.js

export default class ReducerChain {
  constructor(reducers) {
    this.reducers = reducers;

    if (!Array.isArray(reducers)) {
      throw new Error('To create a reducer chain you must pass in an array of functions.');
    }

    return this.reducer;
  }

  reducer = (state, action) => {
    let result = state;

    for (let i = 0, len = this.reducers.length; i < len; i++) {
      result = this.reducers[i](result, action);
    }

    return result;
  };
}

Reducers.js

import ReducerChain from './ReducerChain';

const SOME_ACTION = 'SOME_ACTION';
const SOME_OTHER_ACTION = 'SOME_OTHER_ACTION';

const initialState = {
  someProp: 'someValue',
  someOtherProp: 'someOtherValue',
}

function reducer1 = function (state, action) {
  switch (action.type) {
    case SOME_ACTION:
      return Object.assign({}, state, {
        someProp: 'someNewValue',
      });
    
    default:
      return state;
  }
}

function reducer2 = function (state, action) {
  switch (action.type) {
    case SOME_OTHER_ACTION:
      return Object.assign({}, state, {
        someOtherProp: 'someOtherNewValue',
      });
    
    default:
      return state;
  }
}

export default new ReducerChain([
  reducer1,
  reducer2,
]);