在mongoose中填充对象内的数组

const mongoose = require('mongoose');

const actorSchema = new mongoose.Schema({
  name: String,
  age: Number
});

const movieSchema = new mongoose.Schema({
  title: String,
  actors: [{ type: mongoose.Types.ObjectId, ref: 'Actor' }]
});

const Actor = mongoose.model('Actor', actorSchema);
const Movie = mongoose.model('Movie', movieSchema);

Movie.findOne({ title: 'The Avengers' })
  .populate('actors')
  .exec(function(err, movie) {
    if (err) {
      console.log(err);
    } else {
      console.log(movie);
    }
  });

Movie.findOne({ title: 'The Avengers' })
  .populate('actors director')
  .exec(function(err, movie) {
    if (err) {
      console.log(err);
    } else {
      console.log(movie);
    }
  });