Mongoose从两个集合加载、限制和跳过数据

const UserSchema = new mongoose.Schema({
  name: String,
  posts: [{ type: mongoose.Schema.Types.ObjectId, ref: 'Post' }]
});

const PostSchema = new mongoose.Schema({
  title: String,
  content: String,
  author: { type: mongoose.Schema.Types.ObjectId, ref: 'User' }
});

const User = mongoose.model('User', UserSchema);
const Post = mongoose.model('Post', PostSchema);

// 查询用户，并填充其关联的所有文章
User.findOne({ name: 'John' })
  .populate('posts')
  .exec((err, user) => {
    if (err) {
      console.error(err);
    } else {
      console.log(user);
    }
  });

// 查询文章，并填充其关联的作者
Post.findOne({ title: 'Hello World' })
  .populate('author')
  .exec((err, post) => {
    if (err) {
      console.error(err);
    } else {
      console.log(post);
    }
  });