Dfyjkt

I'm working on a Node.js server, connecting to MongoDB and written with TypeScript. When I try to use MongoDB it doesn't create a connection, however when I check the mongo output it does appear to create a connection.

What am I missing in my code to define the connection in Node.js?

My connection string is 'mongodb://localhost:27017'

My connection method:

connect() 
 console.log('connecting to mongo') //this is called
 MongoClient.connect(this.connectionString, useNewUrlParser: true)
 .then(client => 
 console.log('setting client'); //this doesn't get called
 this.client = client;
 console.log(this.client);
 )
 .catch(error => 
 console.log('error during connecting to mongo: '); //this also doesn't get called
 console.error(error);
 );

Mongo output:

2018-11-08T23:06:24.106+0100 I NETWORK [listener] connection accepted from 127.0.0.1:51345 #11 (2 connections now open)

2018-11-08T23:06:24.107+0100 I NETWORK [conn11] received client metadata from 127.0.0.1:51345 conn11: driver: name: "nodejs", version: "3.1.9" , os: type: "Darwin", name: "darwin", architecture: "x64", version: "17.7.0" , platform: "Node.js v8.9.3, LE, mongodb-core: 3.1.8"

My repository is at https://github.com/FrisoDenijs/MEAN-ToDo/blob/master/server/src/db/mongo.db.ts for the full code.

console.log(db) as asked by shkaper

MongoClient 
 domain: null,
 _events: ,
 _eventsCount: 0,
 _maxListeners: undefined,
 s:
 url: 'mongodb://localhost:27017',
 options:
 servers: [Array],
 caseTranslate: true,
 useNewUrlParser: true,
 socketTimeoutMS: 360000,
 connectTimeoutMS: 30000,
 promiseLibrary: [Function: Promise] ,
 promiseLibrary: [Function: Promise],
 dbCache: ,
 sessions: ,
 topology:
 Server 
 domain: null,
 _events:
 serverOpening: [Function],
 serverDescriptionChanged: [Function],
 serverHeartbeatStarted: [Function],
 serverHeartbeatSucceeded: [Function],
 serverHeartbeatFailed: [Function],
 serverClosed: [Function],
 topologyOpening: [Function],
 topologyClosed: [Function],
 topologyDescriptionChanged: [Function],
 commandStarted: [Function],
 commandSucceeded: [Function],
 commandFailed: [Function],
 joined: [Function],
 left: [Function],
 ping: [Function],
 ha: [Function],
 authenticated: [Function],
 error: [Function],
 timeout: [Function],
 close: [Function],
 parseError: [Function],
 open: [Object],
 fullsetup: [Object],
 all: [Object],
 reconnect: [Function] ,
 _eventsCount: 25,
 _maxListeners: Infinity,
 clientInfo:
 driver: [Object],
 os: [Object],
 platform: 'Node.js v8.9.3, LE' ,
 s:
 coreTopology: [Object],
 sCapabilities: null,
 clonedOptions: [Object],
 reconnect: true,
 emitError: true,
 poolSize: 5,
 storeOptions: [Object],
 store: [Object],
 host: 'localhost',
 port: 27017,
 options: [Object],
 sessionPool: [Object],
 sessions: ,
 promiseLibrary: [Function: Promise] 

The issue is because mongo.connect is async code and controller call it wrongly. so the subsequent line mongo.getDb() will be executed without having this.client initiated properly.

Since you use Typescript, we can use async/await for cleaner code.

async connect() // add async
 console.log('connecting to mongo');

 try 
 if (!this.client) // I added this extra check
 console.log('setting client');
 this.client = await MongoClient.connect(this.connectionString, useNewUrlParser: true )
 console.log(this.client); 
 
 catch(error) 
 console.log('error during connecting to mongo: ');
 console.error(error);
 

And in controller code

async get(req: Request, res: Response) // add async
 const mongo = new MongoDb();
 await mongo.connect(); // add await
 const db = mongo.getDb(); 
 // .... 

I tried your repo with the changes and got this response

Hope it helps

Based on what you said about neither error nor success callbacks being called, I think the problem is not only in code here: https://github.com/FrisoDenijs/MEAN-ToDo/blob/master/server/src/db/mongo.db.ts
But also e.g. here: https://github.com/FrisoDenijs/MEAN-ToDo/blob/master/server/src/controllers/to-do.controller.ts
When you run mongo.connect there should be an option to wait for the promise returned from MongoClient.connect. So I would change code in mongo.db.ts to for example sth like this (it depends how you want to handle this promise):

connect() 
 console.log('connecting to mongo')
 return MongoClient.connect(this.connectionString, useNewUrlParser: true)
 .then(client => 
 console.log('setting client');
 this.client = client;
 console.log(this.client);
 )
 .catch(error => 
 console.log('error during connecting to mongo: ');
 console.error(error);
 );

Then in to-do.controller.ts you can await this or use then:

get(req: Request, res: Response) 
 const mongo = new MongoDb();
 mongo.connect().then(() => 

 const db = mongo.getDb();
 const collection = db.collection('todo', (error, collection) => 
 if (error) 
 res.json(error);
 res.statusCode = HttpStatus.BAD_REQUEST
 return;
 

 collection.find().toArray((error, result) => 
 if (error) 
 res.json(error);
 res.statusCode = HttpStatus.BAD_REQUEST
 

 res.json(result);
 res.statusCode = HttpStatus.OK;
 )

 );

 mongo.close();
 );
 

I suppose that your code just does not "wait" for connection to be established and then fails.