使用回调和promise对mongodb查询的不同响应

const MongoClient = require('mongodb').MongoClient;

// 连接数据库
MongoClient.connect('mongodb://localhost:27017', (err, client) => {
  if (err) {
    console.error('Failed to connect to MongoDB:', err);
    return;
  }

  const db = client.db('mydb');
  const collection = db.collection('mycollection');

  // 查询数据
  collection.find({}).toArray((err, docs) => {
    if (err) {
      console.error('Failed to query data:', err);
      return;
    }

    console.log('Query result:', docs);
    client.close();
  });
});

const MongoClient = require('mongodb').MongoClient;

// 连接数据库
const connectPromise = new Promise((resolve, reject) => {
  MongoClient.connect('mongodb://localhost:27017', (err, client) => {
    if (err) {
      reject(err);
    } else {
      resolve(client);
    }
  });
});

// 查询数据
connectPromise.then((client) => {
  const db = client.db('mydb');
  const collection = db.collection('mycollection');

  return collection.find({}).toArray();
}).then((docs) => {
  console.log('Query result:', docs);
}).catch((err) => {
  console.error('Failed to query data:', err);
}).finally(() => {
  client.close();
});