Youtube in react: comments reducer

comments.js

import {SUCCESS} from '../actions';
import {WATCH_DETAILS} from '../actions/watch';

const initialState = {
  byVideo: {},
  byId: {},
};
export default function (state = initialState, action) {
  switch (action.type) {
    case WATCH_DETAILS[SUCCESS]:
      return reduceWatchDetails(action.response, state);
    default:
      return state;
  }
}