Youtube: watch details reducer: quick and dirty implementation

video.js

function reduceWatchDetails(responses, prevState) {
  let byIdEntry = {};
  if (responses && responses[0].result.items) {
    const video = responses[0].result.items[0];
    byIdEntry = {[video.id]: video};
  }

  return {
    ...prevState,
    byId: {
      ...prevState.byId,
      ...byIdEntry,
    },
  };
}