A correct way in connecting and disconnecting to MongoDb in Node.js

config.js

const url = require("url");
const parsedUrl = url.parse(
  process.env.CONNECTION_STRING || "mongodb://localhost:27017/reactor"
);

module.exports = {
  db: {
    host: parsedUrl.hostname,
    port: parseInt(parsedUrl.port, 10),
    name: parsedUrl.pathname.substr(1),
    user: parsedUrl.auth ? parsedUrl.auth.split(":")[0] : null,
    password: parsedUrl.auth ? parsedUrl.auth.split(":")[1] : null,
    url: parsedUrl.href
  }
};

sample-mongodb-app.js

const express = require("express");
const http = require("http");
const dbConnection = require("./mongoDbConnectionSingleton"); // it is here: https://gist.github.com/peZhmanParsaee/e7e25a17dd36a70bf6289187cab2c994
const app = express();

app.get("/", async (req, res) => {
  try {
    const db = dbConnection.getDb();
    const result = await db.collection("CUSTOMERS").find({}).toArray();
    res.send(result);
  } catch (e) {
    console.error(e);
  }
});

dbConnection
  .getInstance()
  .then((connection) => {
    const server = http.createServer(app);

    server.listen(4445, () => {
      const addr = server.address();
      console.log(
        `API is up and running at ${addr.address} and port number ${addr.port}`
      );
    });
  })
  .catch((e) => {
    console.error(e);
    process.exit(1);
  });