db is not a function error in NodeJS using MongoDB - node.js

Question

I got this error in my application that is previously working
const usersCollection = require('../db').db().collection("users")
^
TypeError: require(...).db is not a function
at Object.<anonymous> (/Users/user/Desktop/sites/app/models/User.js:2:42)
at Module._compile (internal/modules/cjs/loader.js:959:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:995:10)
at Module.load (internal/modules/cjs/loader.js:815:32)
at Function.Module._load (internal/modules/cjs/loader.js:727:14)
at Module.require (internal/modules/cjs/loader.js:852:19)
at require (internal/modules/cjs/helpers.js:74:18)
at Object.<anonymous> (/Users/user/Desktop/sites/app/controllers/userController.js:1:14)
db.js
const dotenv = require('dotenv')
dotenv.config()
const mongodb = require('mongodb')
mongodb.connect(process.env.CONNECTIONSTRING, {useNewUrlParser: true, useUnifiedTopology:
true}, function(err, client) {
module.exports = client
const app = require('./app')
app.listen(process.env.PORT)
})
.env file
CONNECTIONSTRING=mongodb+srv://user:password#sandbox-gk8wp.mongodb.net/db?
retryWrites=true&w=majority
PORT=3000
I have updated also my mongodb npm package from 3.3.3 to 3.4.1 but still the same error. What seems to be the problem?

Answer 1

You are trying to export something in the callback which may or may not be available when you import it as it is asynchronous method. Better way will be to create db.js like
const dotenv = require('dotenv')
dotenv.config()
const mongodb = require('mongodb')
function getMongoClient() {
return mongodb.connect(process.env.CONNECTIONSTRING, {useNewUrlParser: true, useUnifiedTopology: true});
}
module.exports = getMongoClient;
And when you want to use it
const getMongoClient = require('../db');
getMongoClient()
.then(client => client.db().collection("users"));
Hope this helps. You could also use async/await.