Node.js: Express Router, Controllers & Middleware

Learning Objectives

By the end of this lesson, you will be able to:

• Understand Express.js routing fundamentals
• Implement the MVC (Model-View-Controller) architecture in Node.js apps
• Create and organize routes using Express Router
• Build reusable controllers to handle business logic
• Implement custom middleware functions for request processing
• Structure a Node.js application following best practices

Prerequisites

• Basic knowledge of JavaScript
• Familiarity with Node.js fundamentals
• Understanding of HTTP methods (GET, POST, PUT, DELETE)
• Node.js and npm installed on your computer

Table of Contents

1. Introduction to Express.js
2. MVC Architecture Overview
3. Express Routing Basics
4. Express Router
5. Controllers
6. Middleware Concepts
7. Building a Complete API
8. Best Practices
9. Exercises
10. Resources

Introduction to Express.js

Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications. It simplifies the process of building web applications by providing a layer of web application features without obscuring Node.js features.

MVC Architecture Overview

The Model-View-Controller (MVC) pattern separates application concerns:

• Model: Data and business logic
• View: User interface (templates, HTML, etc.)
• Controller: Handles requests, processes data using Models, and returns responses

Express Routing Basics

Routing refers to determining how an application responds to client requests to specific endpoints (URIs) and HTTP methods.

Express Router

Express Router is a mini express application that provides routing APIs like .use(), .get(), .param(), and route().

Controllers

Controllers handle the application logic between models and views. They process incoming requests, interact with models, and send responses back to clients.

Middleware Concepts

Middleware functions are functions that have access to the request object, response object, and the next middleware function. They can:

• Execute code
• Make changes to request/response objects
• End the request-response cycle
• Call the next middleware function

Building a Complete API

We'll put everything together to build a RESTful API following MVC architecture with proper routing and middleware implementation.

Best Practices

• Folder structure recommendations
• Error handling
• Code organization
• Performance considerations

Exercises

1. Create a basic Express application with Router
2. Implement middleware for logging and authentication
3. Build controllers for a simple CRUD application

Resources

• Express.js Documentation
• MDN Web Docs - Express/Node introduction
• Express Router Guide
• Understanding Express.js Middleware