dataLoaders

resolvers.js

const authorsByIds = () => new DataLoader(async ids => {
  const authors = await authorModel.findByIds(ids);
  const authorById = new Map();
  authors.forEach(author => authorById.set(author.id, author));
  return ids.map(id => authorById.get(id));
});

const authorResolver = (source, { id }, context) => {
  let dl = context.dataLoaders.get(authorsById);
  if (!dl) {
    dl = authorsById();
    context.dataLoaders.set(authorsById, dl);
  }
  return dl.load(id)
}