Route prefixing in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a router instance.

Express

const express = require('express');
const router = express.[1]();

Drag options to blanks, or click blank then click option'

ARouter

Broute

Capp

Dlisten

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'route' instead of 'Router' causes an error because 'route' is not a function.

Using 'app' is incorrect because it refers to the main app, not a router.

The Router() method creates a new router object to handle routes.

2fill in blank

medium

Complete the code to prefix all routes in the router with '/api'.

Express

app.use([1], router);

Drag options to blanks, or click blank then click option'

A'/home'

B'/'

C'/user'

D'/api'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '/' will not add any prefix.

Using '/home' or '/user' does not match the required prefix.

The app.use('/api', router) prefixes all routes in the router with '/api'.

3fill in blank

hard

Fix the error in the route definition to respond with 'Hello World'.

Express

router.get('/hello', (req, res) => {
  res.[1]('Hello World');
});

Drag options to blanks, or click blank then click option'

Ajson

Bwrite

Csend

Drender

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'write' causes the response to not end properly.

Using 'render' expects a template, which is not used here.

The res.send() method sends a response body as a string.

4fill in blank

hard

Fill both blanks to create a router that handles GET requests at '/users' and responds with JSON.

Express

router.[1]('/users', (req, res) => {
  res.[2]({ message: 'User list' });
});

Drag options to blanks, or click blank then click option'

Aget

Bsend

Cjson

Dpost

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'post' instead of 'get' changes the route method.

Using 'send' instead of 'json' sends plain text, not JSON.

The get method defines a GET route, and json sends a JSON response.

5fill in blank

hard

Fill all three blanks to prefix routes with '/api', create a POST route at '/login', and send a JSON response.

Express

app.use([1], router);

router.[2]('/login', (req, res) => {
  res.[3]({ success: true });
});

Drag options to blanks, or click blank then click option'

A'/api'

Bpost

Cjson

D'/user'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '/user' as prefix instead of '/api'.

Using 'get' instead of 'post' for the login route.

Using 'send' instead of 'json' for JSON response.

Prefix routes with '/api', define a POST route, and send JSON response.

Practice

1. What is the main purpose of route prefixing in Express?

easy

A. To encrypt route URLs for security

B. To speed up the server response time

C. To automatically generate HTML pages

D. To group routes under a shared path for better organization

Solution

1. Step 1: Understand route prefixing concept

   Route prefixing means putting multiple routes under one common path prefix to keep code organized.

2. Step 2: Identify the main benefit

   This grouping helps keep URLs clean and code easier to maintain by avoiding repetition of the same path.

3. Final Answer:

   To group routes under a shared path for better organization -> Option D

4. Quick Check:

   Route prefixing = Group routes under shared path [OK]

Hint: Route prefixing groups routes by shared path prefix [OK]

Common Mistakes:

• Thinking it improves server speed
• Confusing with automatic HTML generation
• Assuming it encrypts URLs

2. Which of the following is the correct way to prefix routes using Express Router?

easy

A. app.use('/api', router);

B. router.prefix('/api');

C. app.route('/api').use(router);

D. router.attach('/api');

Solution

1. Step 1: Recall Express Router usage

   Express uses app.use(prefix, router) to attach a router with a path prefix.

2. Step 2: Check each option

   Only app.use('/api', router) is valid syntax; others are not Express methods.

3. Final Answer:

   app.use('/api', router); -> Option A

4. Quick Check:

   Prefix routes with app.use(prefix, router) [OK]

Hint: Use app.use('/prefix', router) to prefix routes [OK]

Common Mistakes:

• Using non-existent router.prefix() method
• Trying app.route() to prefix router
• Using router.attach() which doesn't exist

3. Given this code, what URL path will respond with 'Hello World'?

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

router.get('/hello', (req, res) => {
  res.send('Hello World');
});

app.use('/api', router);

medium

A. /hello

B. /api

C. /api/hello

D. /hello/api

Solution

1. Step 1: Understand route prefixing effect

   The router defines '/hello', but it is attached to app with prefix '/api'.

2. Step 2: Combine prefix and route path

   The full path becomes '/api' + '/hello' = '/api/hello'.

3. Final Answer:

   /api/hello -> Option C

4. Quick Check:

   Prefix + route path = full URL [OK]

Hint: Full route = prefix + router path [OK]

Common Mistakes:

• Ignoring the prefix and choosing '/hello'
• Choosing just the prefix '/api' without route
• Reversing prefix and route order

4. Identify the error in this Express route prefixing code:

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

router.get('/test', (req, res) => {
  res.send('Test route');
});

app.use(router, '/api');

medium

A. router.get path should not start with '/'

B. The order of arguments in app.use is incorrect

C. router must be created with express.Route() not express.Router()

D. res.send should be res.json for route prefixing

Solution

1. Step 1: Check app.use argument order

   app.use expects (path, router), but code uses (router, path) which is wrong.

2. Step 2: Confirm other parts are correct

   router.get with '/test' is valid; express.Router() is correct; res.send works fine.

3. Final Answer:

   The order of arguments in app.use is incorrect -> Option B

4. Quick Check:

   app.use(path, router) order matters [OK]

Hint: app.use(path, router) not app.use(router, path) [OK]

Common Mistakes:

• Swapping arguments in app.use
• Thinking router path can't start with '/'
• Confusing express.Router() with express.Route()

5. You want to create two routers: one for '/users' and one for '/products'. How do you correctly prefix and mount them in Express?

hard

A. app.use('/users', usersRouter); app.use('/products', productsRouter);

B. usersRouter.use('/users'); productsRouter.use('/products'); app.use(usersRouter); app.use(productsRouter);

C. app.route('/users').use(usersRouter); app.route('/products').use(productsRouter);

D. app.use(usersRouter, '/users'); app.use(productsRouter, '/products');

Solution

1. Step 1: Understand correct mounting syntax

   To prefix routers, use app.use(prefix, router) for each router separately.

2. Step 2: Evaluate options

   app.use('/users', usersRouter); app.use('/products', productsRouter); correctly uses app.use with prefix and router. Others misuse methods or argument order.

3. Final Answer:

   app.use('/users', usersRouter); app.use('/products', productsRouter); -> Option A

4. Quick Check:

   Mount each router with app.use(prefix, router) [OK]

Hint: Mount each router with app.use('/prefix', router) [OK]

Common Mistakes:

• Using router.use() without attaching to app
• Using app.route() incorrectly for routers
• Swapping arguments in app.use