Youtube in React: video details reducer

videos.js

import {VIDEO_DETAILS, WATCH_DETAILS} from '../actions/watch';
/* ... */
export default function videos(state = initialState, action) {
  switch (action.type) {
    case MOST_POPULAR[SUCCESS]:
      return reduceFetchMostPopularVideos(action.response, state);
    case VIDEO_CATEGORIES[SUCCESS]:
      return reduceFetchVideoCategories(action.response, state);
    case MOST_POPULAR_BY_CATEGORY[SUCCESS]:
      return reduceFetchMostPopularVideosByCategory(action.response, action.categories, state);
    case WATCH_DETAILS[SUCCESS]:
      return reduceWatchDetails(action.response, state);
    case VIDEO_DETAILS[SUCCESS]:
      return reduceVideoDetails(action.response, state);
    default:
      return state;
  }
}
/* ... */