Simplify Redux Reducer

example_reducer.js

const initialState = [];

// Using initialState as a default parameter uses the initial state on first render
export default function (state = initialState, action) {

    switch (action.type) {

        case 'SET_ATTRACTIONS':
            return action.attractions;

        default:
            return state;
    }

}

orig_reducer_combining.js

import { combineReducers } from 'redux';
import reducerEvents from './reducerEvents';
import reducerAttractions from './reducerAttractions';
import reducerGuides from './reducerGuides';
import reducerSponsors from './reducerSponsors';

export default combineReducers({
    events: reducerEvents,
    attractions: reducerAttractions,
    guides: reducerGuides,
    sponsors: reducerSponsors
});

updated_reducer_combining.js

import { combineReducers } from 'redux';

function returnStateSlice(expectedAction, valueKey, state = [], action) {
    if (expectedAction === action.type) return action[valueKey];
    return state;
}

export default combineReducers({
    events: returnStateSlice.bind(null, 'SET_EVENTS', 'events'),
    attractions: returnStateSlice.bind(null, 'SET_ATTRACTIONS', 'attractions'),
    guides: returnStateSlice.bind(null, 'SET_GUIDES', 'guides'),
    sponsors: returnStateSlice.bind(null, 'SET_SPONSORS', 'sponsors')
});

This gist shows how to reduce reducer files! The example_reducer.js simple returns the values provided by the action regardless of the previous state. The orig_reducer_combining.js references four files doing the same thing. This allows use to get rid of the additional files an have all logic in a single two-line function.