Why building HTTP servers matters in Node.js - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a basic HTTP server in Node.js.

Node.js

const http = require('http');
const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end([1]);
});
server.listen(3000, () => {
  console.log('Server running on port 3000');
});

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

A'Hello World!'

B'Goodbye!'

C'Error!'

D'Welcome!'

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect response text

Forgetting to end the response

The server responds with 'Hello World!' text to any request.

2fill in blank

medium

Complete the code to listen on port 8080 instead of 3000.

Node.js

server.listen([1], () => {
  console.log('Server running on port 8080');
});

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

A8080

B3000

C80

D5000

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving the port as 3000

Using a port number below 1024 without permissions

Port 8080 is commonly used for HTTP servers during development.

3fill in blank

hard

Fix the error in the code to properly import the HTTP module using modern ES modules syntax.

Node.js

import [1] from 'http';

const server = http.createServer((req, res) => {
  res.end('Hi');
});

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

Ahttp

B{ http }

CHttp

D* as http

Attempts:

3 left

💡 Hint

Common Mistakes

Using default import syntax which is invalid for 'http' module

Using incorrect casing

Using 'import * as http from "http";' correctly imports the entire module as an object.

4fill in blank

hard

Fill both blanks to send a JSON response with status code 200.

Node.js

const server = http.createServer((req, res) => {
  res.statusCode = [1];
  res.setHeader('Content-Type', [2]);
  res.end(JSON.stringify({ message: 'Success' }));
});

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

A200

B'application/json'

C'text/html'

D404

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong status code

Setting wrong Content-Type header

Status code 200 means OK, and 'application/json' tells the browser the response is JSON.

5fill in blank

hard

Fill all three blanks to create a server that responds with HTML content on port 5000.

Node.js

const server = http.createServer((req, res) => {
  res.statusCode = [1];
  res.setHeader('Content-Type', [2]);
  res.end([3]);
});
server.listen(5000, () => {
  console.log('Server running on port 5000');
});

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

A200

B'text/html'

C'<h1>Welcome!</h1>'

D'application/json'

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong status code

Wrong Content-Type header

Sending plain text instead of HTML

The server sends a 200 OK status, sets the content type to HTML, and sends a simple HTML heading.

Practice

1. Why is building an HTTP server important in Node.js?

easy

A. It automatically fixes bugs in your code.

B. It makes your computer run faster.

C. It allows your computer to share information over the internet.

D. It helps you write desktop applications.

Solution

1. Step 1: Understand the role of HTTP servers

   HTTP servers let computers send and receive information over the internet.

2. Step 2: Connect this to Node.js usage

   Node.js provides tools to build these servers so your app can communicate online.

3. Final Answer:

   It allows your computer to share information over the internet. -> Option C

4. Quick Check:

   HTTP servers = share info online [OK]

Hint: HTTP servers share info online, not speed or desktop apps [OK]

Common Mistakes:

• Thinking HTTP servers speed up the computer
• Confusing servers with desktop app tools
• Believing servers fix code bugs automatically

2. Which of the following is the correct way to create a basic HTTP server in Node.js using ES modules?

easy

A. import http from 'http'; http.createServer((req, res) => res.end('Hello')).listen(3000);

B. const http = require('http'); http.createServer((req, res) => res.end('Hello')).listen(3000);

C. const http = import('http'); http.createServer((req, res) => res.end('Hello')).listen(3000);

D. const http = require('http'); http.createServer((req, res) => res.send('Hello')).listen(3000);

Solution

1. Step 1: Identify modern Node.js import syntax

   Node.js ES modules use import to load modules, not require.

2. Step 2: Check server creation and response method

   http.createServer with res.end() is correct; res.send() is not a Node.js method.

3. Final Answer:

   import http from 'http'; http.createServer((req, res) => res.end('Hello')).listen(3000); -> Option A

4. Quick Check:

   Use import + res.end() in Node.js 20+ [OK]

Hint: Use import and res.end() for Node.js HTTP servers [OK]

Common Mistakes:

• Using require instead of import in ES modules
• Using res.send() which is not in Node.js core
• Trying to import with const and import() function

3. What will this Node.js HTTP server print when accessed?

import http from 'http';
const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');
  res.end('Welcome!');
});
server.listen(3000);

medium

A. Error: statusCode is not a property

B. Welcome!

C. undefined

D. Content-Type header missing

Solution

1. Step 1: Analyze server response setup

   The server sets status code 200, sets Content-Type header, and ends response with 'Welcome!'.

2. Step 2: Understand what client receives

   The client will get a plain text response with 'Welcome!' and status 200.

3. Final Answer:

   Welcome! -> Option B

4. Quick Check:

   res.end('Welcome!') sends text response [OK]

Hint: res.end sends the response body text [OK]

Common Mistakes:

• Thinking statusCode is invalid property
• Expecting undefined instead of response text
• Ignoring headers set by setHeader

4. Identify the error in this Node.js HTTP server code:

import http from 'http';
const server = http.createServer((req, res) => {
  res.write('Hello');
  res.write('World');
  res.end();
});
server.listen(3000);

medium

A. No error, code works fine

B. Cannot call res.write multiple times

C. Missing res.end() call

D. res.end() should have a string argument

Solution

1. Step 1: Review usage of res.write and res.end

   Node.js allows multiple res.write calls before res.end to send chunks.

2. Step 2: Confirm res.end usage

   Calling res.end() without argument is valid; it ends the response.

3. Final Answer:

   No error, code works fine -> Option A

4. Quick Check:

   Multiple res.write calls + res.end() is valid [OK]

Hint: Multiple res.write calls are allowed before res.end [OK]

Common Mistakes:

• Thinking res.end must have argument
• Believing multiple res.write calls cause error
• Forgetting res.end is needed to finish response

5. You want to build a Node.js HTTP server that responds with JSON data and handles errors gracefully. Which approach is best?

hard

A. Use http.createServer, set Content-Type to application/json, but do not handle errors.

B. Use http.createServer, send JSON as plain text, ignore errors to keep server fast.

C. Use http.createServer, set Content-Type to text/html, and send JSON string directly.

D. Use http.createServer, set Content-Type to application/json, and wrap response code in try-catch.

Solution

1. Step 1: Set correct Content-Type for JSON

   To send JSON, Content-Type must be 'application/json' so clients parse it properly.

2. Step 2: Handle errors gracefully

   Wrapping response code in try-catch prevents server crashes and sends error info.

3. Final Answer:

   Use http.createServer, set Content-Type to application/json, and wrap response code in try-catch. -> Option D

4. Quick Check:

   JSON needs correct header + error handling [OK]

Hint: Always set JSON header and catch errors in server code [OK]

Common Mistakes:

• Sending JSON with wrong Content-Type
• Ignoring errors causing server crashes
• Using text/html header for JSON data