mongoose connection nodejs

mongoose.connect('mongodb://localhost:27017/test', {
  useMongoClient: true,
  connectTimeoutMS: 1000
})mongoose.connect('mongodb://localhost/myapp', { useNewUrlParser: true, useUnifiedTopology: true });
mongoose.connect('mongodb://username:password@host:port/database?options...', {useNewUrlParser: true});const mongoose = require('mongoose');

const connectDB = async () => {
    mongoose
        .connect('mongodb://localhost:27017/playground', {
            useCreateIndex: true,
            useNewUrlParser: true,
            useUnifiedTopology: true,
            useFindAndModify: false
        })
        .then(() => console.log('Connected Successfully'))
        .catch((err) => console.error('Not Connected'));
}

module.exports = connectDB;