MongoClient.connect('mongodb://127.0.0.1:27017/exampleDB', (err, client) => {
    console.log(client);
    client.close();
});

MongoClient {
  domain: null,
  _events: {},
  _eventsCount: 0,
  _maxListeners: undefined,
  s:
   { url: 'mongodb://127.0.0.1:27017/aircraftDB',
     options:
      { socketOptions: {},
        read_preference_tags: null,
        readPreference: [ReadPreference],
        dbName: 'aircraftDB',
        servers: [Array],
        server_options: [Object],
        db_options: [Object],
        rs_options: [Object],
        mongos_options: [Object],
        socketTimeoutMS: 360000,
        connectTimeoutMS: 30000,
        promiseLibrary: [Function: Promise] },
     promiseLibrary: [Function: Promise],
     dbCache: {},
     sessions: [] },
  topology:
   Server {
     domain: null,
     _events:
      { serverOpening: [Function],
        serverDescriptionChanged: [Function],
        serverHeartbeatStarted: [Function],
        serverHeartbeatSucceeded: [Function],
        serverHeartbeatFailed: [Function],
        serverClosed: [Function],
        topologyOpening: [Function],
        topologyClosed: [Function],
        topologyDescriptionChanged: [Function],
        joined: [Function],
        left: [Function],
        ping: [Function],
        ha: [Function],
        authenticated: [Function],
        error: [Function],
        timeout: [Function],
        close: [Function],
        parseError: [Function],
        open: [Function],
        fullsetup: [Function],
        all: [Function],
        reconnect: [Function] },
     _eventsCount: 22,
     _maxListeners: Infinity,
     clientInfo:
      { driver: [Object],
        os: [Object],
        platform: 'Node.js v9.2.0, LE' },
     s:
      { coreTopology: [Server],
        sCapabilities: null,
        clonedOptions: [Object],
        reconnect: true,
        emitError: true,
        poolSize: 5,
        storeOptions: [Object],
        store: [Store],
        host: '127.0.0.1',
        port: 27017,
        options: [Object],
        sessionPool: [ServerSessionPool],
        sessions: [],
        promiseLibrary: [Function: Promise] } } }