Connecting MongoDB database in Node JS

server.js

// Connecting database
DB_URL = 'mongodb://localhost:27017/todo'
mongoose.connect(DB_URL, { useNewUrlParser: true, useUnifiedTopology: true, useFindAndModify: false, useCreateIndex: true })
mongoose.connection.once('open', () => {
    console.log('Connected to database');
}).on('error', (error) => {
    console.log(`There is an error in connecting database: ${error}`);
});