'use strict'; const mongodb = require('mongodb'); const Dao = require('./dao.js'); const ObjectID = mongodb.ObjectID; var url = 'mongodb://...'; var data = { name: 'Jill' }; var database; mongodb.MongoClient.connect(url).then(db => { database = db; return db.collection('test-collection').insertOne(data); }).then(() => { closeDb(database) }).catch(error => { closeDb(database); throw error; }); function closeDb(database) { if (database) { database.close(); } }