connect to mongo database from node server

server.js

const mongoose = require('mongoose');

mongoose.connect(
    'mongodb://username:password@host/databasename', {useNewUrlParser: true}
);

const db = mongoose.connection;

db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function () {
    console.log("you are connected to the database")
});