Dynamically create a react redux reducer

react-create-reducer-dynamically.js

export function createReducer(initialState, reducerMap) {
    return (state = initialState, action) => {
        const reducer = reducerMap[action.type];

        return reducer
            ? reducer(state, action.payload)
            : state;
    };
}

// used in the example below

import {createReducer} from '../../utils';
// Add the following for IE compatability
Object.assign = Object.assign || require('object-assign'); 

const initialState = {
   'count': 0,
   'receiving': false,
   'pages': 0,
   'documents': []
};

export default createReducer(initialState, {
    ['RECEIVED_DOCUMENTS']: (state, payload) => {
        return {
            'count': payload.count,
            'pages': payload.pages,
            'documents': payload.documents,
            'receiving': false
        };
    },
    ['RETRIVING_DOCUMENTS']: (state, payload) => {
        return Object.assign({}, state, {
            'receiving': true
        });
    }
});