JSFiddle - React, Tailwind, and code Playground

HTML

<title>
  
  MondoDb in nodeJs implementation with promise and callback
  
</title>

JavaScript

'use strict';

var MongoClient = require('mongodb').MongoClient;

var coll='dbName';
var dbName='mongodb://localhost:27017/' + coll;
var connectingDb; //promise

init();

module.exports = {
    connectingDb: connectingDb,
    getFromMongo: getFromMongo
};

function init() {
    console.log('================== initializing DB ========================');

    connectingDb = new Promise((resolve, reject) =>{

        console.log('using: '+dbName);

        MongoClient.connect(
            dbName,
            {
                db: { bufferMaxEntries: 0 }
            },
            function(err, db) {
                if(err){
                    console.error('Failed to connect to mongo on startup', err);
                    reject(err);
                }

                else {
                    console.log("Connected correctly to mongo db server.");
                    resolve(db);
                }
            }
        );
    });

}

function getFromMongo(cb) {
     connectingDb.then(function(db) {

        db.collection(coll).find().toArray(function (err,result){
            cb(result);
        });

     });
}