如何全局使用MongoDB连接

const { MongoClient } = require('mongodb');

// MongoDB连接字符串
const url = 'mongodb://localhost:27017';
const dbName = 'myDatabase';

// 创建MongoDB客户端实例
let mongoClient;

// 初始化数据库连接
async function initializeDbConnection() {
  try {
    mongoClient = new MongoClient(url, { useUnifiedTopology: true });
    await mongoClient.connect();
    console.log('Connected to MongoDB');
  } catch (error) {
    console.error('Failed to connect to MongoDB', error);
  }
}

// 获取数据库实例
function getDb() {
  if (!mongoClient) {
    throw new Error('Database connection not initialized');
  }
  return mongoClient.db(dbName);
}

// 在应用程序启动时调用初始化函数
initializeDbConnection();

module.exports = { getDb };

const { getDb } = require('./path/to/db');

async function run() {
  const db = getDb();
  const collection = db.collection('myCollection');
  
  // 执行数据库操作
  const result = await collection.find({}).toArray();
  console.log(result);
}

run().catch(console.error);