Node.js and Express

Notes from the summary of COMP3011 Lecture 6, 7, and online resources.

Introduction to Node.js and Express.js

Node.js is a runtime environment that allows you to run JavaScript on the server side (outside the browser).

Express.js is a web framework built on top of Node.js to simplify server-side development.

JavaScript Libraries

Popular frontend libraries and frameworks include:

• React – for building interactive UIs.
• Vue.js – lightweight and beginner-friendly.
• jQuery – DOM manipulation and AJAX (older but still relevant).

Key Concepts

Node.js (Backend)

• JavaScript runtime outside the browser.
• Built on Chrome’s V8 engine.
• Asynchronous, event-driven, scalable.
• Used for backend services and APIs.

REST (Representational State Transfer)

• Web service architecture using standard HTTP methods.
• Stateless communication.
• CRUD operations:
  • GET: Retrieve data.
  • POST: Create new data.
  • PUT: Update existing data.
  • DELETE: Remove data.

Express.js

• Node.js web application framework.
• Simplifies web server and API development.
• Provides routing, middleware, and HTTP handling.

Practical Implementation

• Setup:
  • Install Node.js and npm.
  • npm init to initialize a project.
  • npm install express to add Express.js.
• Basic Web Server:
  • Use app.get(), app.post(), app.put(), app.delete().
  • Serve HTML via res.sendFile().
  • Use nodemon for auto-reload.
• Route Parameters & Query Strings:
  • Extract and handle values from URLs.
• Form Handling:
  • Use body-parser to process form data.
• Testing:
  • Use Postman to test API endpoints.
• Validation:
  • Use Joi for input validation.
• Security:
  • Intro to basic authentication concepts.

Key Takeaways

• Node.js + Express.js = powerful backend stack.
• RESTful API design is crucial.
• Tools like Postman and Joi streamline development.
• Middleware is fundamental for building robust Express apps.

Advanced Express, MongoDB, Templates

Revision

• Nodemon: Auto restart server.
• Joi: Request validation.
• Body-parser: Parses incoming request bodies.

Middleware in Express

• Middleware functions have access to req, res, next.
• Types:
  • Application-level: app.use()
  • Router-level: router.use()
  • Error-handling: (err, req, res, next)
  • Built-in: express.static, express.json()
  • Third-party: body-parser, cookie-parser, morgan

Authentication & Authorization

• Authentication: Verifying identity.
• Authorization: Determining access rights.
• JWT: Stateless authentication via JSON Web Tokens.
  • npm install jsonwebtoken
• Passport.js:
  • Popular middleware for user authentication.
  • Supports local and OAuth strategies.
  • Example: passport-local, express-session setup.

MongoDB

• NoSQL document database (stores JSON-like documents).
• Collections = Tables; Documents = Rows.
• Use MongoDB Atlas for cloud hosting.

Mongoose (ODM)

• Defines Schemas for MongoDB collections.
• Create and manage documents with Models.
• npm install mongoose
• Connect with mongoose.connect().
• CRUD operations:
  • .find(), .findOne(), .deleteOne(), .save()
• Handle IDs with mongoose.Types.ObjectId()

Templates

• Used for rendering HTML with dynamic content.

EJS

• Install: npm install ejs
• Setup: app.set('view engine', 'ejs')
• Files: views/index.ejs

Pug

• Install: npm install pug
• Setup: app.set('view engine', 'pug')
• Syntax is whitespace-sensitive.
• Load static files via express.static('public')

AJAX

• Use jQuery ajax() for DELETE requests in the front-end.

Exercises

• Practice building an Express + MongoDB app.
• Render tasks with Pug.
• Add delete buttons with AJAX handling.
• Serve static files (CSS/JS) with express.static().

Summary

• Covered middleware, authentication, MongoDB integration with Mongoose, and template rendering using EJS and Pug.
• Built full-stack capabilities with modern JavaScript tools.