Connecting Mongodb databse to node.js server

Question

I have been trying to make a web app using node.js and express and decided to work with mongodb. I am using mongodb node.js driver version: 4.3.1 I have tried all the possible ways to connect the node.js server with my mongodb atlas database.

My database also got connected using the following code in my db.js file:

const app = require('./app');

const MongoClient = require('mongodb').MongoClient

const Url = 'mongodb+srv://todoAppUser:<myOriginalPasswordHere>@cluster0.6lvjr.mongodb.net/myDatabase?retryWrites=true&w=majority';

MongoClient.connect(Url, function (err, client) {
  if (err) throw err;

  var db = client.db('myDatabase');

  db.collection('products').findOne({}, function (findErr, result) {
    if (findErr) throw findErr;
    console.log(result.name);
    client.close();
  });
});

The above code works fine and gives the output as well. But I want to use MVC (Model-view-Controller) framework for which I need to export the connection.

I made the following change in the above code:

MongoClient.connect(Url, function (err, client) {
  if (err) throw err;

  var db = client.db('myDatabase');

  db.collection('products').findOne({}, function (findErr, result) {
    if (findErr) throw findErr;
    console.log(result.name);
  module.exports = db
    client.close();
  });
});

After the change when I try to access my connection (const productCollection = require('./db').collection("product");) from any other file of mine, it gives me the following error:

const productCollection = require('./db').collection("product");
                                          ^

TypeError: require(...).collection is not a function
    at Object.<anonymous> (D:\Kush- Complete Data\exp-projects\nodeApp\productController.js:1:43)
    at Module._compile (internal/modules/cjs/loader.js:1072:14)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1101:10)
    at Module.load (internal/modules/cjs/loader.js:937:32)
    at Function.Module._load (internal/modules/cjs/loader.js:778:12)
    at Module.require (internal/modules/cjs/loader.js:961:19)
    at require (internal/modules/cjs/helpers.js:92:18)
    at Object.<anonymous> (D:\Kush- Complete Data\exp-projects\nodeApp\router.js:3:27)
    at Module._compile (internal/modules/cjs/loader.js:1072:14)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1101:10)
[nodemon] app crashed - waiting for file changes before starting...

May anyone please guide me and show a possible way out.

Thanks, Kush

Answer 1

[SOLVED] I figured out, in newer versions of mongodb they have essentially changed the way of connecting node server to the database. To establish a reusable connection (So that we can access the connected database from any other file), I created an async function in my db.js file where connection is established and then exported it. In the end of the file, I have called the function. The code is as follows:

 const {MongoClient} = require('mongodb')
    
    
    const client = new MongoClient('mongodb+srv://todoAppUser:<password>@cluster0.6lvjr.mongodb.net/myDatabase?retryWrites=true&w=majority')
    
    async function start(){
      await client.connect()
      console.log("Connected")
      module.exports = client.db()
      const app = require('./app')
      app.listen(3000)
    }
    
      start()

and while calling it from another file:

const productCollection = require('./db').collection("product");

This code gives me no error and works perfectly fine. With the help of the above code, one can use this conveniently while following the MVC (Model-View-Controller) framework.