Routing requests manually in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a basic HTTP server that listens on port 3000.

Node.js

const http = require('http');

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Hello World');
});

server.listen([1], () => {
  console.log('Server running');
});

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

A5000

B3000

C8080

D80

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number for the port.

Choosing a port that is already in use.

The server listens on port 3000, which is a common port for local development.

2fill in blank

medium

Complete the code to check the request URL and respond with 'Home Page' if the path is '/'.

Node.js

const http = require('http');

const server = http.createServer((req, res) => {
  if (req.url === [1]) {
    res.statusCode = 200;
    res.end('Home Page');
  } else {
    res.statusCode = 404;
    res.end('Not Found');
  }
});

server.listen(3000);

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

A'/main'

B'/home'

C'/index'

D'/'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '/home' instead of '/' for the home page.

Forgetting to include quotes around the path string.

The root path '/' is used to represent the home page URL.

3fill in blank

hard

Fix the error in the code to respond with 'About Page' when the URL is '/about'.

Node.js

const http = require('http');

const server = http.createServer((req, res) => {
  if (req.url === [1]) {
    res.statusCode = 200;
    res.end('About Page');
  } else {
    res.statusCode = 404;
    res.end('Not Found');
  }
});

server.listen(3000);

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

A'/About'

B'about'

C'/about'

D'about/'

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the leading slash in the path string.

Using incorrect case or trailing slashes.

The URL path must start with a slash '/' to match the request URL correctly.

4fill in blank

hard

Fill both blanks to respond with JSON data when the URL is '/api/data'.

Node.js

const http = require('http');

const server = http.createServer((req, res) => {
  if (req.url === [1]) {
    res.statusCode = 200;
    res.setHeader('Content-Type', [2]);
    res.end(JSON.stringify({ message: 'Hello API' }));
  } else {
    res.statusCode = 404;
    res.end('Not Found');
  }
});

server.listen(3000);

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

A'/api/data'

B'text/html'

C'application/json'

D'/data/api'

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong URL path or swapping the URL and Content-Type values.

Setting Content-Type to 'text/html' for JSON data.

The URL must match '/api/data' exactly, and the Content-Type header should be 'application/json' to indicate JSON data.

5fill in blank

hard

Fill all three blanks to route requests to different responses for '/', '/about', and '/contact'.

Node.js

const http = require('http');

const server = http.createServer((req, res) => {
  if (req.url === [1]) {
    res.end('Home Page');
  } else if (req.url === [2]) {
    res.end('About Page');
  } else if (req.url === [3]) {
    res.end('Contact Page');
  } else {
    res.statusCode = 404;
    res.end('Not Found');
  }
});

server.listen(3000);

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

A'/'

B'/about'

C'/contact'

D'/home'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '/home' instead of '/' for the home page.

Mixing up the paths or missing the leading slash.

Each URL path must match exactly the route to respond with the correct page.

Practice

1. What is the main purpose of checking req.url in a Node.js server without frameworks?

easy

A. To decide how to respond to different request paths

B. To parse the request body automatically

C. To connect to a database

D. To handle user authentication

Solution

1. Step 1: Understand the role of req.url

   req.url contains the path requested by the client, like '/home' or '/about'.

2. Step 2: Purpose of checking req.url

   By checking req.url, the server can decide which content or response to send back.

3. Final Answer:

   To decide how to respond to different request paths -> Option A

4. Quick Check:

   Routing = Check req.url [OK]

Hint: Check req.url to route requests manually [OK]

Common Mistakes:

• Thinking req.url parses request body
• Confusing req.url with database connection
• Assuming req.url handles authentication

2. Which of the following is the correct way to send a plain text response with status 200 in a manual Node.js server?

easy

A. res.status(200).send('Hello');

B. res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello');

C. res.sendStatus(200).send('Hello');

D. res.write(200, 'Hello');

Solution

1. Step 1: Identify correct methods for manual response

   In manual Node.js servers, res.writeHead() sets status and headers, res.end() sends the response body.

2. Step 2: Check each option

   res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello'); uses writeHead and end correctly. The second and third options use Express methods, not native Node.js. res.write(200, 'Hello'); is invalid syntax.

3. Final Answer:

   res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello'); -> Option B

4. Quick Check:

   Manual response = writeHead + end [OK]

Hint: Use writeHead and end to send manual responses [OK]

Common Mistakes:

• Using Express methods in plain Node.js
• Calling res.write without headers
• Incorrect method names like res.sendStatus

3. What will the following Node.js server code output when a client requests /hello?

const http = require('http');
const server = http.createServer((req, res) => {
  if (req.url === '/hello') {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Hello World');
  } else {
    res.writeHead(404);
    res.end('Not Found');
  }
});
server.listen(3000);

medium

A. Error: Cannot read property 'writeHead' of undefined

B. Not Found

C. Hello World

D. Server crashes

Solution

1. Step 1: Check the request URL condition

   The code checks if req.url === '/hello'. If true, it sends 'Hello World' with status 200.

2. Step 2: Determine output for '/hello'

   Since the request is '/hello', the first branch runs, sending 'Hello World'.

3. Final Answer:

   Hello World -> Option C

4. Quick Check:

   req.url '/hello' = 'Hello World' [OK]

Hint: Match req.url exactly to send correct response [OK]

Common Mistakes:

• Assuming default response is 'Hello World'
• Confusing 404 and 200 responses
• Expecting server error without syntax issues

4. Identify the error in this manual routing code snippet:

const http = require('http');
const server = http.createServer((req, res) => {
  if (req.url = '/test') {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Test page');
  } else {
    res.writeHead(404);
    res.end('Page not found');
  }
});
server.listen(3000);

medium

A. Missing res.end() call

B. server.listen() missing port number

C. Incorrect header format in writeHead

D. Using assignment (=) instead of comparison (===) in if condition

Solution

1. Step 1: Check the if condition syntax

   The condition uses req.url = '/test', which assigns instead of compares. This always evaluates to true.

2. Step 2: Identify correct comparison operator

   It should be req.url === '/test' to compare values properly.

3. Final Answer:

   Using assignment (=) instead of comparison (===) in if condition -> Option D

4. Quick Check:

   Use === for comparison, not = [OK]

Hint: Use === for comparison, not = [OK]

Common Mistakes:

• Confusing assignment and comparison operators
• Forgetting to call res.end()
• Incorrect header object syntax

5. You want to manually route requests to serve JSON data at /data and plain text at /info. Which code snippet correctly implements this?

hard

A. if (req.url === '/data') { res.writeHead(200, {'Content-Type': 'application/json'}); res.end(JSON.stringify({name: 'Node'})); } else if (req.url === '/info') { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Information'); } else { res.writeHead(404); res.end('Not Found'); }

B. if (req.url === '/data') { res.end({name: 'Node'}); } else if (req.url === '/info') { res.end('Information'); } else { res.end('Not Found'); }

C. if (req.url === '/data') { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('{"name":"Node"}'); } else if (req.url === '/info') { res.writeHead(200, {'Content-Type': 'application/json'}); res.end('Information'); } else { res.writeHead(404); res.end('Not Found'); }

D. if (req.url === '/data') { res.writeHead(404); res.end('Not Found'); } else if (req.url === '/info') { res.writeHead(200); res.end('Information'); }

Solution

1. Step 1: Check content types for each route

   For /data, JSON content type 'application/json' is correct. For /info, plain text 'text/plain' is correct.

2. Step 2: Verify response body and headers

   if (req.url === '/data') { res.writeHead(200, {'Content-Type': 'application/json'}); res.end(JSON.stringify({name: 'Node'})); } else if (req.url === '/info') { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Information'); } else { res.writeHead(404); res.end('Not Found'); } sets correct headers and uses JSON.stringify for JSON data. Other options misuse content types or omit headers.

3. Final Answer:

   correctly sets headers and responses for both routes -> Option A

4. Quick Check:

   Set correct Content-Type and stringify JSON [OK]

Hint: Set Content-Type and stringify JSON for JSON responses [OK]

Common Mistakes:

• Sending JSON object directly without stringify
• Mixing content types for routes
• Omitting status codes or headers