在填充的数组中填充Mongoose并选择一个字段

const mongoose = require('mongoose');

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

const postSchema = new mongoose.Schema({
  title: String,
  content: String
});

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

const user = new User({
  name: 'John Doe',
  posts: [post1Id, post2Id, ...] // 假设post1Id、post2Id为已存在的帖子ID
});

const post1 = new Post({
  title: 'Post 1',
  content: 'Content of post 1'
});

const post2 = new Post({
  title: 'Post 2',
  content: 'Content of post 2'
});

user.save();
post1.save();
post2.save();

User.findOne({ name: 'John Doe' })
  .populate('posts')
  .exec((err, user) => {
    if (err) {
      console.error(err);
      return;
    }

    console.log(user.posts); // 输出填充后的帖子数据
  });