Here's a simple way to think about the difference between Express.js and Node.js:

• Express.js is like a house. It provides the structure and foundation that you need to build your web application.
• Node.js is like the land that the house is built on. It provides the underlying infrastructure that allows Express.js to work. Without Express.js, you could still build a web application using Node.js, but it would be much more difficult and time-consuming. Express.js provides a number of features that make it much easier to build web applications, such as routing, templating, and error handling.

1. Install Node.js: Before installing Express.js, you need to have Node.js installed on your computer. You can download the installer from the official Node.js website (opens in a new tab).

2. Create a new project: Open your command line interface (CLI) and navigate to the directory where you want to create your new project. Then, run the following command to create a new directory for your project and navigate into it:

mkdir myapp
cd myapp

3. Initialize your project: In the myapp directory, run the following command to initialize your project and create a package.json file:

npm init

Follow the prompts to enter information about your project.

4. Install Express.js: In the myapp directory, run the following command to install Express.js and save it as a dependency in your package.json file:

npm install express --save

5. Create an Express.js app: In the myapp directory, create a new file called app.js. This file will contain the code for your Express.js app. Here is some sample code to get you started:

// Require the express module, which is a web framework for Node.js
const express = require('express');
// Create an app object by calling the express function
const app = express();
 
// Define a route handler for the root path ('/')
app.get('/', function (req, res) {
 // Use the res object to send a text message 'Hello World!' back to the client
 res.send('Hello World!');
});
 
// Tell the app to listen on port 3000
app.listen(3000, function () {
 // Log a message 'Example app listening on port 3000!' to the terminal when the app starts listening
 console.log('Example app listening on port 3000!');
});

6. Run your app: In the CLI, navigate to the myapp directory and run the following command to start your app:

node app.js

You should see a message that says "Example app listening on port 3000!".

7. Test your app: Open your web browser and navigate to http://localhost:3000. You should see a message that says "Hello World!".

That's it! You have successfully installed Express.js and created a simple app.

1. We need to import express module in our project.

const express = require("express")

2. We need to create a express app.

const app = express()

3. We need to create a route for our app.

• get, post, put, delete are the methods used to create a route for our app.
• get() method is used to create a route for our app and it takes two arguments first is the route and second is the callback function which will be executed when the route is accessed by the user.
• The get() method is used to create a route for a GET request. A GET request is a type of HTTP request that is used to retrieve data from a server. In this case, we are telling Express.js to return the message "Hello World!" when a user visits the URL /.
• The callback function takes two arguments first is the request object and second is the response object. The request object contains the information about the request made by the user and the response object contains the information about the response that will be sent to the user.
• send() method is used to send the response to the user.

//Home Page
app.get(`/`, (req, res) => {
  res.send("This is our main Page");
});
 
//About Page
app.get(`/about`, (req, res) => {
  res.send("This is our about Page");
});
 
//Contact Page
app.get(`/contact`, (req, res) => {
  res.send("This is our contact Page");
});

4. We need to listen to the port for our app.

• listen() method is used to listen to the port for our app and it takes two arguments first is the port number and second is the callback function which will be executed when the port is listening.

//Server
app.listen(5001);

You can simply pass the port number as an argument to the listen() method.

5. Now we need to run our app.

node app.js

6. Go to the browser

• Now open your browser and type http://localhost:5001 in the address bar and press enter you will see the message This is our main Page on the screen.
• Now type http://localhost:5001/about in the address bar and press enter you will see the message This is our about Page on the screen.
• Now type http://localhost:5001/contact in the address bar and press enter you will see the message This is our contact Page on the screen.