如何避免在对象内部创建对象，并在express中使用mongoose直接将元素推入数组？

const mongoose = require('mongoose');

const userSchema = new mongoose.Schema({
  favorites: [{
    type: mongoose.Schema.Types.ObjectId,
    ref: 'Favorite'
  }]
});

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

module.exports = User;

const express = require('express');
const router = express.Router();
const User = require('../models/user');
const Favorite = require('../models/favorite');

router.post('/users/:userId/favorites', async (req, res) => {
  try {
    const { userId } = req.params;
    const { favoriteId } = req.body;

    // 创建Favorite对象
    const favorite = new Favorite({ _id: favoriteId });

    // 查找用户并将Favorite对象推入favorites数组
    const user = await User.findById(userId);
    user.favorites.push(favorite);

    // 保存用户对象
    await user.save();

    res.status(200).json({ message: 'Favorite added successfully' });
  } catch (error) {
    res.status(500).json({ error: 'An error occurred' });
  }
});

module.exports = router;