How can I create a shared database mongo object and use in migrate nodejs file?

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Javascript

MongoDB

Node.js

, +

For my express.js project, I use the migrate package to manage the Models of my Mongo database.
I defined database object in db.js file.Then I used it in migrate file.

//db.js file
const mongoClient = require('mongodb').MongoClient;
    const mongoDbUrl = 'mongodb://127.0.0.1:27017/mydb';
    let mongodb;

    function connect(callback){
        mongoClient.connect(mongoDbUrl, (err, db) => {
            mongodb = db;
            callback();
        });
    }
    function get(){
        return mongodb;
    }

    function close(){
        mongodb.close();
    }

    module.exports = {
        connect,
        get,
        close
    };

'use strict'
// db is just an object shared between the migrations
var myDB = require('../db/db.js');


module.exports.up = function (next) {

  myDB.connect(function (err, client) {
    if (err) {
      console.log(err);
    }
    else {
      // start the rest of your app here
      
    }

  });

  console.log("MyDB=" + myDB.get());

  next()
}

module.exports.down = function (next) {
  next()
}

But it does not work and lists my return as undefined...Can any guide me for example how can I create a shared DB object and use it in another js file...

sp@sp-HP-ProBook-4530s:~/Documents/express$ migrate
  up : 1648736072728-posts.js
MyDB=undefined
  migration : complete

Thanks in advance


https://www.npmjs.com/package/migrate[migrate package link]

What I have tried:

I created an example but it does not work...
javascript - How to properly reuse connection to Mongodb across NodeJs application and modules - Stack Overflow[^]