Why Routing requests manually in Node.js? - Purpose & Use Cases

The Big Idea

Discover how routing can turn your messy URL checks into clean, easy-to-manage code!

The Scenario

Imagine building a website where every time a user clicks a link, you have to check the URL and decide what content to show by writing many if-else statements.

The Problem

Manually checking URLs is slow, messy, and easy to make mistakes. It becomes hard to add new pages or fix bugs because the code is tangled and repetitive.

The Solution

Routing libraries automatically match URLs to the right code, keeping your project organized and making it easy to add or change pages without confusion.

Before vs After

✗ Before

if (url === '/home') { showHome(); } else if (url === '/about') { showAbout(); } else { show404(); }

✓ After

router.get('/home', showHome);
router.get('/about', showAbout);
router.use(show404);

What It Enables

It lets you build clear, scalable websites where each URL leads to the right content without messy code.

Real Life Example

Think of an online store where URLs like '/products' and '/cart' automatically show the right pages without you writing complex checks for each one.

Key Takeaways

Manual URL checks get complicated and error-prone quickly.

Routing libraries organize URL handling cleanly.

This makes websites easier to build and maintain.

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