mongodb nodejs connect localhost

1//with mongoose 
2
3const mongoose = require('mongoose');
4
5mongoose.connect(
6    mongoURI,
7    {
8        useNewUrlParser: true,
9        useUnifiedTopology: true
10    },
11    (err) => {
12        if (err) console.log(err);
13        app.listen(3000);
14    }
15);
16/********************************************************************/
17// with mongodb lib
18const mongodb = require('mongodb');
19
20const MongoClient = mongodb.MongoClient;
21
22let _db;
23// you can replace test with any database name that you want
24const mongoConnect = (cb) => {
25  MongoClient.connect('mongodb://127.0.0.1:27017/test')
26    .then((client) => {
27      _db = client.db();
28      cb()
29      console.log('Connected to MongoDb');
30    }).catch((err) => {
31      console.log(err);
32    });
33}
34//after your server started you can use getDb to access mongo Database
35const getDb = () => {
36  if (_db) return _db;
37  throw 'No database found';
38}
39
40exports.mongoConnect = mongoConnect;
41exports.getDb = getDb;

1"mongodb://localhost:27017/MyDb"