Lecture Notes on Node.js and Express.js

Overview

• NOJ (Node.js): An open-source cross-platform JavaScript runtime environment.
  • Built on the V8 JavaScript engine from Google Chrome.
  • Enables server-side and networking applications with user interactivity.
  • Features like asynchronous I/O, event-driven architecture, and the npm package manager.
  • Applications: Dynamic web applications, authentication, authorization, and security.
  • Key Concepts: ES6 features (Arrow Functions, Callbacks, Promises), Node Package Manager (NPM), Express Framework, and various modules.

Setting Up Node.js

• Installation: Use command line npm init and npm install to set up projects and manage packages.
• Core Concepts: Command line interface, folder structures, basic server setup, error handling.
• Modules: Core modules like OS, Path, FS, HTTP for various operations.

Express Framework

• Express.js: Node.js web application framework to build single-page, multi-page, and hybrid web applications.
  • Simplifies server creation, routing, middleware handling, and HTTP requests.
  • Installation: npm install express and set up basic server infrastructure.
  • Basic Setup: app.js file, require Express library, create server, handle requests and responses.

File System (FS) Module

• File Operations: Creating, reading, updating, and deleting files using FS module.
• Key Methods: fs.readFile, fs.writeFile, fs.rename, fs.unlink.
• Example: Read a file and log content or handle errors.

Modules and Packages

• Understanding Packages: Use require to import Core and Third-party modules, like Express.js.
• Creating Custom Modules: Example of creating addition, subtraction, multiplication, and division modules.
• Exporting Modules: Use module.exports to make functions available for importing in other files.

HTTP Module

• Server Creation: Using http.createServer to handle HTTP requests and responses.
• Routing Basics: Handling different routes and sending responses accordingly.

RESTful API Development

• API Concepts: Creating APIs for CRUD (Create, Read, Update, Delete) operations.
• Express Routes: Define routes for handling requests using Express Router, and creating corresponding controllers for business logic.
• Data Models: Define MongoDB models using Mongoose to interact with database collections.
  • Example: Employee schema with fields like name, email, phone, city.

Authentication and Authorization

• Authentication Basics: Identifying users with methods including sessions and tokens (JWT - JSON Web Tokens).
• Session Management: Using Express-session to maintain session data and user identities across requests.
• JWT Tokens: Implementation of JWT for secure authentication and creating protected routes based on token validation.
  • Example: Encoding/decoding tokens, implementing middleware for token verification.

Middleware in Express

• Middleware Functions: Intercepting requests to process before reaching the final handler or route.
• Example Use-cases: Logging, validation, authentication, modifying requests, and error handling.

Database Integration

• MongoDB with Mongoose: Setting up connections and performing CRUD operations through schemas and models.
• Database Operations: Creating models for user data, handling CRUD operations with Mongoose methods.

Deployment and Scaling

• Deployment Strategies: Basic introduction to deploying Node.js applications on servers and handling environment-specific configurations.
• Scaling: Using clusters and load balancers to handle multiple requests and ensure high availability.

Advanced Topics

• Real-time Applications: Intro to building real-time applications with technologies like WebSocket integrated with Node.js.
• Error Handling: Centralizing error handling logic using middleware and custom error classes.
• Testing: Overview on unit testing Express applications with frameworks like Mocha and Chai.

Summary

• We covered a comprehensive overview of Node.js, Express.js, REST APIs, authentication/authorization, middleware, database integration, and deploying Node.js applications.
• Practical examples were provided to illustrate key concepts like server creation, routing, file operations, and managing dependencies with NPM.