Installing Express and Mongoose-

1. Install the required libraries by running the command:

npm i express

npm i mongoose

Connecting to a Database:

1. Install nodemon by the following command and answer some basic questions:

    npm i -D nodemon
   

2. Make two files index.js and db.js

3. Inside db.js , Connect to MongoDB using mongoose.connect method. This method takes a connection string as the first parameter and options as the second parameter. Here's an example of connecting to MongoDB:

   
    const connectToMongo = () => {
        const mongoose = require("mongoose");
        const Url = 'mongodb://localhost:27017';
        mongoose.connect(Url, {
                useNewUrlParser: true
            })
            .then(() => {
                console.log("connected to database mongodb");
            })
            .catch((err) => {
                console.log("Error", err);
            });
    };
   

   1. Don't forget to export this function ,then In your index.js file add the following command:

1.  module.exports = connectToMongo;
   

    //index.js
    const connectToMongo = require('./db');
    connectToMongo();
   

   That's it you are successfully connected to MongoDB.

   Setup Express Server:

   Here are the basic steps to set up an Express server:

   1. Install Express by running the command npm install express in your project directory.

   2. Create a new file in your project directory called index.js

   3. Import the Express library at the top of your index.js file using the following code:

       const express = require('express');
      

   4. Create a new instance of the Express application by calling the express() method :

       const app = express();
      

   5. Define a route by calling one of the HTTP methods (e.g. app.get(), app.post(), app.put(), etc.) on your app object. Here's an example of defining a route for the root path of your application:

       app.get('/', (req, res) => {
         res.send('Hello, World!');
       });
      

   6. Start the server by calling the listen() method on your index object. This method takes a port number and an optional callback function as parameters. Here's an example of starting the server on port 3000:

       const port = 3000;
      
       app.listen(port, () => {
         console.log(`Server started on port ${port}`);
       });
      

   7. Run your server by executing the node index.js command in your terminal.

That's it! You now have a basic Express server set up that will respond with "Hello, World!" when you navigate to the root path of your application in a web browser or make a GET request to the root path using a tool like Postman, cURL or thunderclient. You can add additional routes, middleware, and functionality to your server as needed to build out your application.