Youtube in React: search for videos reducer

search.js

function reduceSearchForVideos(response, searchQuery, prevState) {
  let searchResults = response.items.map(item => ({...item, id: item.id.videoId}));
  if (prevState.query === searchQuery) {
    const prevResults = prevState.results || [];
    searchResults = prevResults.concat(searchResults);
  }
  return {
    totalResults: response.pageInfo.totalResults,
    nextPageToken: response.nextPageToken,
    query: searchQuery,
    results: searchResults
  };
}