Node JS - Mongoose -如何通过ID正确连接两个集合的结果

const mongoose = require('mongoose');

// 定义User集合的数据模型
const userSchema = new mongoose.Schema({
  name: String,
  age: Number,
  email: String
});

const User = mongoose.model('User', userSchema);

// 定义Post集合的数据模型
const postSchema = new mongoose.Schema({
  title: String,
  content: String,
  author: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'User' // 引用User集合
  }
});

const Post = mongoose.model('Post', postSchema);

// 创建一条User数据
const user = new User({
  name: 'John',
  age: 25,
  email: 'john@example.com'
});

// 创建一条Post数据，并将author字段设置为user的ID
const post = new Post({
  title: 'Hello World',
  content: 'This is my first post',
  author: user._id
});

Post.findById(postId)
  .populate('author') // 使用populate方法填充author字段
  .exec((err, post) => {
    if (err) {
      console.error(err);
    } else {
      console.log(post.title);
      console.log(post.content);
      console.log(post.author.name);
      console.log(post.author.age);
      console.log(post.author.email);
    }
  });