Routing requests manually in Node.js

Introduction

Routing requests manually means deciding what to do based on the web address a user visits. It helps your server send the right response for each request.

You want to handle different web pages or API endpoints without using extra libraries.

You are learning how web servers work by controlling requests step-by-step.

You need a simple server that responds differently based on the URL path.

You want to customize how your server reacts to specific URLs or HTTP methods.

Syntax

Node.js

const http = require('http');

const server = http.createServer((req, res) => {
  if (req.url === '/') {
    // handle root path
  } else if (req.url === '/about') {
    // handle about page
  } else {
    // handle 404 not found
  }
});

server.listen(3000);

Use req.url to check the requested path.

Use res.writeHead() and res.end() to send responses.

Examples

Responds with 'Home page' when the root URL is requested.

Node.js

if (req.url === '/') {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Home page');
}

Responds with 'About us' when the '/about' URL is requested.

Node.js

if (req.url === '/about') {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('About us');
}

Sends a 404 error message for unknown URLs.

Node.js

res.writeHead(404, {'Content-Type': 'text/plain'});
res.end('Page not found');

Sample Program

This server listens on port 3000. It sends a welcome message for the root URL, contact info for '/contact', and a 404 message for other URLs.

Node.js

const http = require('http');

const server = http.createServer((req, res) => {
  if (req.url === '/') {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Welcome to the Home page!');
  } else if (req.url === '/contact') {
    res.writeHead(200, {'Content-Type': 'text/plain'});
    res.end('Contact us at [e-mail]');
  } else {
    res.writeHead(404, {'Content-Type': 'text/plain'});
    res.end('404: Page not found');
  }
});

server.listen(3000, () => {
  console.log('Server running at http://localhost:3000/');
});

Important Notes

Check req.method if you want to handle GET, POST, or other HTTP methods differently.

Manual routing is simple but can get hard to manage for many routes; frameworks help with this.

Summary

Manual routing uses req.url to decide how to respond.

Use res.writeHead() and res.end() to send responses.

This method is good for learning or small servers without extra tools.

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