如何从数组Mongoose中输出值？

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

// 定义一个Schema
const userSchema = new Schema({
  name: String,
  hobbies: [String]
});

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

// 查询所有用户的爱好
User.find({}, 'hobbies', function(err, users) {
  if (err) return console.error(err);
  console.log(users);
});

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

// 定义一个Schema
const postSchema = new Schema({
  title: String,
  author: { type: Schema.Types.ObjectId, ref: 'User' }
});

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

// 定义User Schema
const userSchema = new Schema({
  name: String,
  email: String
});

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

// 查询所有帖子并填充作者信息
Post.find({})
.populate('author')
.exec(function(err, posts) {
  if (err) return console.error(err);
  console.log(posts);
});

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

// 定义一个Schema
const orderSchema = new Schema({
  items: [{
    name: String,
    price: Number
  }]
});

const Order = mongoose.model('Order', orderSchema);

// 查询所有订单，并且只返回价格大于10的物品
Order.aggregate([
  { $unwind: '$items' },
  { $match: { 'items.price': { $gt: 10 } } },
  { $group: { _id: '$_id', items: { $push: '$items' } } }
]).exec(function(err, orders) {
  if (err) return console.error(err);
  console.log(orders);
});

const mongoose = require('mongoose');
const Schema = mongoose.Schema;

// 定义一个Schema
const bookSchema = new Schema({
  title: String,
  tags: [String]
});

const Book = mongoose.model('Book', bookSchema);

// 查询所有带有特定标签的书籍
Book.find({ tags: 'fiction' }).exec(function(err, books) {
  if (err) return console.error(err);
  console.log(books);
});