graphql__egghead_tutorial/src/data/index.js

const videoA = {
  id: 'a',
  title: 'Create a GraphQL schema',
  duration: 120,
  watched: true
};

const videoB = {
  id: 'b',
  title: 'Ember.js CLI',
  duration: 240,
  watched: false
};

const videos = [videoA, videoB];

const createVideo = ({ title, duration, released }) => {
  const video = {
    id: (new Buffer(title, 'utf8')).toString('base64'),
    title,
    duration,
    released
  };
  videos.push(video);
  return video;
};

const getVideoById = (id) => new Promise((resolve) => {
  const [video] = videos.filter(currentVideo => currentVideo.id === id);

  resolve(video);
});

// Shortcut: we have the data immediately, so no promise.
// const getVideos = () => videos;

// General case: asynchronously load the videos
const getVideos = () => new Promise(resolve => resolve(videos));

const getObjectById = (type, id) => {
  const types = {
    video: getVideoById
  };

  return types[type](id);
};

exports.createVideo = createVideo;
exports.getObjectById = getObjectById;
exports.getVideoById = getVideoById;
exports.getVideos = getVideos;