在forEach中查询Mongo DB和Node的其他集合

const MongoClient = require('mongodb').MongoClient;
const url = 'mongodb://localhost:27017'; // MongoDB数据库的连接URL
const dbName = 'mydb'; // 数据库名称

MongoClient.connect(url, function(err, client) {
  if (err) {
    console.error('Failed to connect to database:', err);
    return;
  }

  console.log('Connected successfully to database');

  const db = client.db(dbName);

  // 在这里执行查询操作
});

const usersCollection = db.collection('users');

usersCollection.find().forEach(function(user) {
  const userId = user._id;

  // 查询另一个集合
  const ordersCollection = db.collection('orders');
  ordersCollection.find({ userId: userId }).toArray(function(err, orders) {
    if (err) {
      console.error('Failed to query orders:', err);
      return;
    }

    console.log('User orders:', orders);
  });
});