NodeJS ExpressJS Framework Syllabus

ExpressJS Framework syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for ExpressJS Framework in NodeJS, not a summary of it.

1. 1

   Introduction to ExpressJS

   2 topics

   • What is ExpressJS?
   • Setting Up ExpressJS
2. 2

   Middleware

   3 topics

   • Built-in Middleware
   • Third-party Middleware
   • Custom Middleware
3. 3

   Routing in ExpressJS

   3 topics

   • Basic Routing
   • Route Parameters
   • Router Module
4. 4

   Error Handling

   2 topics

   • Error Handling Middleware
   • Centralized Error Handling

ExpressJS Framework flashcards for NodeJS

21 of 51 cards from the ExpressJS Framework deck — real questions with worked answers.

1. What is ExpressJS?

   ExpressJS is a minimal, unopinionated, and flexible web application framework for Node.js that provides a thin layer of features (routing, middleware, HTTP utilities) for building web servers and RESTful APIs.

2. On which runtime and language does ExpressJS run?

   It runs on the Node.js runtime and is written in JavaScript, building on top of Node's built-in HTTP module.

3. Name three core things ExpressJS simplifies compared to using Node's raw 'http' module.

   Routing (mapping URLs/HTTP methods to handlers), middleware processing of requests/responses, and sending responses (e.g. res.json, res.send, res.status).

4. What does it mean that Express is 'unopinionated'?

   It does not enforce a specific project structure, ORM, or way of doing things; developers are free to organize files and choose their own libraries and patterns.

5. Which two objects are central to nearly every Express handler, and what do they represent?

   The request object (req), representing the incoming HTTP request, and the response object (res), used to build and send the HTTP response back to the client.

6. Which npm command installs ExpressJS into a project as a dependency?

   npm install express (optionally 'npm install express --save' on older npm versions, though --save is the default now).

7. What is the minimal code to create an Express application instance?

   const express = require('express'); const app = express(); — 'express()' returns the application object.

8. How do you start an Express server listening on port 3000?

   app.listen(3000, () => console.log('Server running')); — app.listen binds and listens for connections on the given port.

9. What file typically records Express and its version, and how is a fresh one created?

   package.json records dependencies; it is created with 'npm init' (or 'npm init -y' for defaults) before installing Express.

10. What is the conventional entry-point filename for an Express app, and what does 'require' do?

    Conventionally app.js, index.js, or server.js; require() is the CommonJS function used to import the express module and other dependencies.

11. Define 'middleware' in Express.

    Middleware is a function with access to the request object (req), the response object (res), and the next function in the request-response cycle; it can run code, modify req/res, end the cycle, or call next() to pass control.

12. What is the standard signature of an Express middleware function?

    function(req, res, next) { ... } — three parameters: request, response, and the next() callback that passes control to the following middleware.

13. What happens if a middleware function neither ends the response nor calls next()?

    The request hangs (is left pending) because control is never passed on and no response is sent to the client.

14. What is built-in middleware in Express, and name the three provided by Express 4.16+?

    Middleware bundled with Express itself (no extra install). The three are express.json(), express.urlencoded(), and express.static().

15. What does express.json() do?

    It parses incoming requests with JSON payloads (Content-Type application/json) and populates req.body with the resulting JavaScript object.

16. What does express.urlencoded() parse, and what does the { extended: true } option control?

    It parses URL-encoded form bodies (application/x-www-form-urlencoded) into req.body; extended: true uses the qs library allowing rich/nested objects, while extended: false uses the querystring library (flat data only).

17. What is express.static() used for?

    It serves static files (HTML, CSS, images, JS) from a specified directory, e.g. app.use(express.static('public')).

18. What is third-party middleware, and how is it added to an app?

    Middleware written by external packages installed via npm; it is added with app.use() (or on specific routes) after being required, e.g. app.use(morgan('dev')).

19. Name a common third-party middleware for HTTP request logging.

    morgan — logs incoming HTTP requests with details like method, URL, status, and response time.

20. Which third-party middleware is commonly used to parse cookies, and what does it populate?

    cookie-parser; it parses the Cookie header and populates req.cookies with an object of cookie name/value pairs.

21. Which third-party middleware enables Cross-Origin Resource Sharing in Express?

    cors — it sets the appropriate Access-Control-Allow-* headers to permit requests from other origins.

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