MongoClient.connect('mongodb://localhost:27017/myNewDB',function (err,db) {
    if(err) 
        console.log("Unable to connect DB. Error: " + err)
    else 
        console.log('Connected to DB');

    db.close();
});

myNewDB is DB name, if it does not exists in database then it will create automatically with this call.

  var MongoClient = require('mongodb').MongoClient;
    
    //connection with mongoDB
    MongoClient.connect("mongodb://localhost:27017/MyDb", function (err, db) {
          //check the connection
 if(err){
           console.log("connection failed.");      
}else{
                    console.log("successfully connected to mongoDB.");
    });