NodeJS mongo等待/异步函数

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

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');

  collection.find({}).toArray((err, docs) => {
    if (err) {
      console.error('Failed to fetch documents:', err);
      return;
    }

    console.log('Fetched documents:', docs);
    client.close();
  });
});

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

MongoClient.connect('mongodb://localhost:27017')
  .then(client => {
    const db = client.db('mydb');
    const collection = db.collection('mycollection');

    return collection.find({}).toArray()
      .then(docs => {
        console.log('Fetched documents:', docs);
        client.close();
      });
  })
  .catch(err => {
    console.error('Failed to connect to MongoDB:', err);
  });

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

async function fetchData() {
  try {
    const client = await MongoClient.connect('mongodb://localhost:27017');
    const db = client.db('mydb');
    const collection = db.collection('mycollection');

    const docs = await collection.find({}).toArray();
    console.log('Fetched documents:', docs);

    client.close();
  } catch (err) {
    console.error('Failed to connect to MongoDB:', err);
  }
}

fetchData();