Routing requests manually in Node.js - Mini Project: Build & Apply

Routing requests manually

📖 Scenario: You are building a simple Node.js server that handles different web page requests manually without using any routing libraries.This is like being a traffic controller who directs cars (requests) to the right destination (response) based on the road signs (URL paths).

🎯 Goal: Create a Node.js server that listens on port 3000 and responds with different messages for the paths /, /about, and /contact. For any other path, respond with a 404 message.

📋 What You'll Learn

Create a basic HTTP server using Node.js http module

Add a variable to store the port number 3000

Use if statements to check the request URL and send different responses

Send a 404 response for unknown paths

💡 Why This Matters

🌍 Real World

Manual routing is the foundation of web servers. Understanding it helps you grasp how frameworks like Express work behind the scenes.

💼 Career

Many backend jobs require knowledge of how HTTP servers handle requests and routes, even if you use frameworks. This skill helps in debugging and customizing server behavior.

1

Create a basic HTTP server

Write code to import the http module and create a server using http.createServer that takes req and res parameters. For now, respond with "Hello World" for every request.

Node.js

const http = require('http');

// Your code here

Hint

Use require('http') to import the module. Then create the server with http.createServer((req, res) => { ... }).

2

Add a port variable

Create a constant variable called port and set it to 3000.

Node.js

const http = require('http');

// Your code here

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

Hint

Use const port = 3000; to store the port number.

3

Add routing logic for different paths

Inside the server callback, use if statements to check req.url. If it is "/", respond with "Home Page". If it is "/about", respond with "About Page". If it is "/contact", respond with "Contact Page". For any other URL, respond with "Page Not Found" and set status code to 404.

Node.js

const http = require('http');

const port = 3000;

const server = http.createServer((req, res) => {
  // Your code here
});

Hint

Use if and else if to check req.url and respond accordingly.

4

Start the server listening on the port

Add code to make the server listen on the port variable. Use server.listen(port).

Node.js

const http = require('http');

const port = 3000;

const server = http.createServer((req, res) => {
  if (req.url === '/') {
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/plain');
    res.end('Home Page');
  } else if (req.url === '/about') {
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/plain');
    res.end('About Page');
  } else if (req.url === '/contact') {
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/plain');
    res.end('Contact Page');
  } else {
    res.statusCode = 404;
    res.setHeader('Content-Type', 'text/plain');
    res.end('Page Not Found');
  }
});

// Your code here

Hint

Use server.listen(port); to start the server.

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