如何使用nodejs和mongodb正确处理promise

const MongoClient = require('mongodb').MongoClient;
const url = 'mongodb://localhost:27017/mydb';

function findDocuments() {
  return new Promise((resolve, reject) => {
    MongoClient.connect(url, (err, db) => {
      if (err) reject(err);
      const collection = db.collection('documents');
      collection.find({}).toArray((err, docs) => {
        if (err) reject(err);
        resolve(docs);
        db.close();
      });
    });
  });
}

findDocuments()
  .then(docs => {
    console.log(docs);
  })
  .catch(err => {
    console.error(err);
  });

const MongoClient = require('mongodb').MongoClient;
const url = 'mongodb://localhost:27017/mydb';

function insertDocument(document) {
  return new Promise((resolve, reject) => {
    MongoClient.connect(url, (err, db) => {
      if (err) reject(err);
      const collection = db.collection('documents');
      collection.insertOne(document, (err, result) => {
        if (err) reject(err);
        resolve(result);
        db.close();
      });
    });
  });
}

insertDocument({ name: 'John', age: 25 })
  .then(result => {
    console.log('Document inserted');
  })
  .catch(err => {
    console.error(err);
  });