Resource-based route organization in Express - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Express route handler?

Consider this Express route setup for a resource /books. What will be the response when a GET request is made to /books/42?

Express

const express = require('express');
const app = express();

app.get('/books/:id', (req, res) => {
  res.send(`Book ID is ${req.params.id}`);
});

// Assume app.listen is called elsewhere

A 404 Not Found

B Book ID is 42

C Error: Cannot read property 'id' of undefined

D Book ID is :id

💡 Hint

Look at how req.params works in Express routes with parameters.

The route /books/:id captures the part after /books/ as req.params.id. So when you visit /books/42, req.params.id is 42. The handler sends back Book ID is 42.

📝 Syntax

intermediate

Which option correctly defines a resource route for creating a new user?

You want to add a POST route to /users to create a new user. Which code snippet correctly sets this up in Express?

A app.post('/users', (req, res) => { res.send('User created'); });

B app.get('/users/create', (req, res) => { res.send('User created'); });

C app.put('/users', (req, res) => { res.send('User created'); });

D app.post('/users/:id', (req, res) => { res.send('User created'); });

💡 Hint

Think about which HTTP method is used to create resources and the typical URL pattern.

POST to /users is the standard way to create a new user resource. GET is for reading, PUT is for updating, and POST with an ID in the URL is unusual for creation.

🔧 Debug

advanced

Why does this resource route handler not respond as expected?

Given this Express route, a GET request to /products/123 hangs and never sends a response. What is the cause?

Express

app.get('/products/:id', (req, res) => {
  const productId = req.params.id;
  // Missing res.send or res.end
});

A The handler does not send a response, so the request hangs.

B The route path is incorrect; it should be '/product/:id'.

C req.params.id is undefined causing an error.

D Express requires next() to be called to complete the request.

💡 Hint

Check if the handler sends a response back to the client.

The route handler reads the parameter but never calls res.send() or similar. Without sending a response, the client waits indefinitely.

🧠 Conceptual

advanced

What is the main benefit of organizing routes by resource in Express?

Why do developers prefer grouping routes by resource (like /users, /orders) in Express applications?

A It prevents unauthorized access by restricting routes to resource folders.

B It improves server performance by caching resource routes automatically.

C It allows Express to automatically generate HTML views for each resource.

D It makes the code easier to maintain and understand by keeping related routes together.

💡 Hint

Think about how organizing code affects readability and maintenance.

Grouping routes by resource helps developers find and update related routes easily. It does not affect performance, view generation, or security directly.

❓ state_output

expert

What is the final value of the variable routesCount after this Express router setup?

Given this code that organizes routes for a resource, what is the value of routesCount after all routes are added?

Express

const express = require('express');
const router = express.Router();

let routesCount = 0;

router.get('/', (req, res) => res.send('List'));
routesCount++;

router.post('/', (req, res) => res.send('Create'));
routesCount++;

router.get('/:id', (req, res) => res.send('Read'));
routesCount++;

router.put('/:id', (req, res) => res.send('Update'));
routesCount++;

router.delete('/:id', (req, res) => res.send('Delete'));
routesCount++;

module.exports = router;

A 6

B 4

C 5

D 0

💡 Hint

Count how many routes are defined and increment routesCount.

There are exactly 5 routes defined: GET /, POST /, GET /:id, PUT /:id, DELETE /:id. Each increments routesCount by 1, so final value is 5.

Practice

1. What is the main benefit of organizing routes by resource in an Express app?

easy

A. It groups related routes together for better code organization.

B. It automatically generates HTML pages for each resource.

C. It prevents users from accessing the API without a password.

D. It makes the server run faster by caching routes.

Solution

1. Step 1: Understand resource-based route organization

   Resource-based organization groups routes by the data or resource they manage, like users or products.

2. Step 2: Identify the main benefit

   This grouping helps keep code modular and easier to maintain by keeping related routes together.

3. Final Answer:

   It groups related routes together for better code organization. -> Option A

4. Quick Check:

   Grouping routes by resource = better organization [OK]

Hint: Think about grouping similar things together for neatness [OK]

Common Mistakes:

• Confusing route grouping with security features
• Assuming route organization affects server speed
• Thinking routes auto-generate HTML pages

2. Which of the following is the correct way to create a router for a resource named books in Express?

easy

A. const booksRouter = new express.Router();

B. const booksRouter = express.createRouter();

C. const booksRouter = express.Router();

D. const booksRouter = express.route('books');

Solution

1. Step 1: Recall Express Router creation syntax

   Express provides a Router() method on the express object to create modular route handlers.

2. Step 2: Match the correct syntax

   The correct syntax is express.Router(), not createRouter() or new express.Router().

3. Final Answer:

   const booksRouter = express.Router(); -> Option C

4. Quick Check:

   Use express.Router() to create routers [OK]

Hint: Remember: Router is a method, not a constructor or create function [OK]

Common Mistakes:

• Using new keyword with Router
• Calling a non-existent createRouter method
• Using express.route instead of express.Router

3. Given this Express router code for a users resource:

const express = require('express');
const router = express.Router();

router.get('/', (req, res) => res.send('List users'));
router.post('/', (req, res) => res.send('Create user'));
router.get('/:id', (req, res) => res.send(`Get user ${req.params.id}`));

module.exports = router;

What will be the response when a client sends a GET request to /users/42?

medium

A. List users

B. Get user 42

C. 404 Not Found

D. Create user

Solution

1. Step 1: Identify the matching route for GET /users/42

   The route router.get('/:id', ...) matches GET requests with a parameter after /users/.

2. Step 2: Understand the response sent

   The handler sends back the string Get user 42 using the id parameter from the URL.

3. Final Answer:

   Get user 42 -> Option B

4. Quick Check:

   GET /users/:id returns 'Get user {id}' [OK]

Hint: Match URL pattern with route parameters carefully [OK]

Common Mistakes:

• Confusing POST and GET routes
• Ignoring route parameters in URL
• Assuming root path '/' matches /users/42

4. Consider this Express router code snippet:

const router = express.Router();

router.get('/items', (req, res) => res.send('All items'));
router.get('/items/:id', (req, res) => res.send(`Item ${req.params.id}`));
router.post('/items', (req, res) => res.send('Add item'));

module.exports = router;

When mounting this router in the main app with app.use('/api', router);, what is the correct URL to get the response 'Item 5'?

medium

A. /api/items/5

B. /items/5

C. /api/items

D. /items

Solution

1. Step 1: Understand router mounting path

   The router is mounted at /api, so all routes inside it are prefixed with /api.

2. Step 2: Match the route for getting item with id 5

   The route /items/:id inside the router becomes /api/items/:id in the app.

3. Final Answer:

   /api/items/5 -> Option A

4. Quick Check:

   Router prefix + route path = full URL [OK]

Hint: Add router prefix before route path when calling URLs [OK]

Common Mistakes:

• Ignoring the router prefix when calling URLs
• Using root path instead of mounted path
• Confusing POST and GET URLs

5. You want to organize routes for a products resource using Express Router. You need to support listing all products, creating a product, getting a product by ID, updating a product by ID, and deleting a product by ID.

Which of the following router setups correctly implements all these routes following resource-based route organization?

hard

A. const router = express.Router();
router.get('/products', ...);
router.post('/products', ...);
router.get('/products/:id', ...);
router.put('/products/:id', ...);
router.delete('/products/:id', ...);

B. const router = express.Router();
router.get('/list', ...);
router.post('/create', ...);
router.get('/get/:id', ...);
router.put('/update/:id', ...);
router.delete('/delete/:id', ...);

C. const router = express.Router();
router.get('/products/all', ...);
router.post('/products/new', ...);
router.get('/products/get/:id', ...);
router.put('/products/update/:id', ...);
router.delete('/products/remove/:id', ...);

D. const router = express.Router();
router.get('/', ...);
router.post('/', ...);
router.get('/:id', ...);
router.put('/:id', ...);
router.delete('/:id', ...);

Solution

1. Step 1: Understand resource-based route organization with routers

   When using Express Router for a resource, routes inside the router use relative paths like '/', '/:id' because the router is mounted on the resource path (e.g., '/products').

2. Step 2: Identify the correct route paths

   const router = express.Router(); router.get('/', ...); router.post('/', ...); router.get('/:id', ...); router.put('/:id', ...); router.delete('/:id', ...); uses relative paths inside the router, which is the correct pattern. The router would be mounted with app.use('/products', router).

3. Step 3: Compare with other options

   const router = express.Router(); router.get('/products', ...); router.post('/products', ...); router.get('/products/:id', ...); router.put('/products/:id', ...); router.delete('/products/:id', ...); repeats the resource name in every route, which is redundant inside a router. The remaining options use non-standard paths that don't follow REST conventions.

4. Final Answer:

   const router = express.Router(); router.get('/', ...); router.post('/', ...); router.get('/:id', ...); router.put('/:id', ...); router.delete('/:id', ...); -> Option D

5. Quick Check:

   Use relative paths in router, mount on resource path [OK]

Hint: Inside router, use relative paths; mount router on resource path [OK]

Common Mistakes:

• Repeating resource name in every route inside router
• Using non-RESTful or verbose route paths
• Not mounting router on resource path