Express.Js Introduction

Express.Js Introduction


Lesson 17: Introduction to Express.js



Introduce Express.js as a web application framework for Node.js.


Express.js, a powerful and minimalist web framework for Node.js, simplifies backend development. Let's explore its core concepts and functionalities:


 Overview of Express.js and its role in backend development

- Express.js: Lightweight and flexible, it streamlines routing, middleware, and HTTP handling for Node.js.

- Backend role: Facilitates the creation of robust APIs and web applications, handling HTTP requests and responses efficiently.


 Middleware and routing in Express

- Middleware: Functions executed during the request-response cycle, handling tasks like logging, authentication, etc.

- Routing: Defines endpoints and HTTP methods to handle client requests, aiding in the organization of code.


 Basic server setup using Express

- Server creation: Setting up a basic Express server involves importing the framework, defining routes, and starting the server.

- Example:


  const express = require('express');

  const app = express();

  app.get('/', (req, res) => {

    res.send('Hello, Express!');


  app.listen(3000, () => {

    console.log('Server running on port 3000');



 Lesson 18: Setup Environment of Express.js



Guide students through setting up the development environment for Express.js.


 Installation and configuration of Express.js

- Installation: Use npm (Node Package Manager) to install Express.js in your project.

- Configuration: Initialize and configure Express, set up routes, and handle dependencies.


 Use of tools like Nodemon for automatic server restarts

- Nodemon: A development tool that monitors changes in your source code and automatically restarts the server.

- Benefits: Saves time by eliminating the need to manually restart the server after code changes.


 Folder structure and project setup

- Organized structure: Create folders for routes, controllers, models, views, and other resources to maintain a structured project.

- Example:


  - project-root

    - node_modules

    - app.js

    - routes

      - index.js

    - controllers

      - mainController.js

    - models

      - dataModel.js

    - views

      - index.ejs

    - public

      - css

      - js


 Lesson 19: HTTP Methods



Understand different HTTP methods and their usage in Express.js.


 Overview of HTTP methods (GET, POST, PUT, DELETE)

- GET: Retrieves data from the server.

- POST: Sends data to the server to create a new resource.

- PUT: Updates an existing resource on the server.

- DELETE: Removes data from the server.


 Handling different types of requests in Express

- Routing: Define routes for different HTTP methods, handling specific tasks or data manipulations.

- Middleware: Use middleware to intercept and process incoming requests before reaching the route handlers.


 RESTful API principles and routing

- RESTful APIs: Follows principles like statelessness, uniform interface, and resource-based URLs for efficient and scalable APIs.

- Routing: Express allows developers to create RESTful routes that adhere to these principles.

 Lesson 20: Request & Response Objects



Explore the request and response objects in Express.js.


 Accessing request parameters and body

- Request object: Contains information about the HTTP request, including query parameters, URL parameters, and request body data.

- Example:


  app.get('/users/:id', (req, res) => {

    const userId =; // Access URL parameter

    const username = req.query.username; // Access query parameter

    const userData = req.body; // Access request body

    // Process the data

    res.send('User data retrieved');




 Sending different types of responses

- Response object: Allows sending various types of responses like HTML, JSON, files, etc., to the client.

- Example:


  app.get('/api/data', (req, res) => {

    const data = { key: 'value' };

    res.json(data); // Send JSON response



 Error handling and middleware for requests and responses

- Error handling: Use middleware to catch errors and handle them gracefully, ensuring a good user experience.

- Middleware for requests and responses: Customize request and response behavior using middleware functions.


Understanding Express.js fundamentals, middleware, routing, and request/response handling lays a strong foundation for developing robust backend applications and RESTful APIs using Node.js.