Creating a basic HTTP server in Node.js - Practice Exercises

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this basic HTTP server response?

Consider this Node.js HTTP server code. What will the server send back to the client when accessed?

Node.js

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

A The server responds with JSON: { message: 'Hello, world!' }

B The server responds with plain text: 'Hello, world!'

C The server responds with HTML content containing 'Hello, world!'

D The server throws an error because of missing response end

💡 Hint

Look at the content type and the string passed to res.end.

The server sets the content type to 'text/plain' and sends the string 'Hello, world!' as the response body.

📝 Syntax

intermediate

Which option contains a syntax error in creating an HTTP server?

Identify the option that will cause a syntax error when creating a basic HTTP server in Node.js.

A ;)0003(netsil.revres ;)} ;)'iH'(dne.ser { >= )ser ,qer((revreSetaerc.ptth = revres tsnoc ;'ptth' morf ptth tropmi

B const http = require('http'); const server = http.createServer((req, res) => { res.end('Hi'); }); server.listen(3000);

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

D mport http from 'http'; const server = http.createServer((req, res) => { res.end('Hi'); }); server.listen(3000);

💡 Hint

Look for missing punctuation or misplaced code inside the callback.

Option C is missing a semicolon or closing brace before calling server.listen, causing a syntax error.

❓ state_output

advanced

What is the value of 'count' after 3 client requests?

This server counts how many requests it has handled. What is the value of 'count' after 3 requests?

Node.js

import http from 'http';
let count = 0;
const server = http.createServer((req, res) => {
  count++;
  res.end(`Request number: ${count}`);
});
server.listen(3000);

A 3

B 1

C 0

D Undefined

💡 Hint

The count variable increases each time the server handles a request.

Each request increments count by 1, so after 3 requests, count is 3.

🔧 Debug

advanced

Which option causes the server to crash on request?

One of these server codes will crash when a client makes a request. Identify which one.

A import http from 'http'; const server = http.createServer((req, res) => { res.end('OK'); res.end('Again'); }); server.listen(3000);

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

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

D import http from 'http'; const server = http.createServer((req, res) => { res.statusCode = 200; res.end('OK'); }); server.listen(3000);

💡 Hint

Check if the response is properly ended.

Option A calls res.end twice, causing a 'write after end' error that crashes the server.

🧠 Conceptual

expert

What happens if server.listen is called twice on the same port?

Consider calling server.listen(3000) twice on the same HTTP server instance. What will happen?

A The server listens twice on port 3000 without error.

B The server restarts and resets all state.

C The server silently ignores the second listen call.

D The second call throws an error because the port is already in use.

💡 Hint

Ports can only be bound once per server instance.

Calling listen twice on the same port causes an error because the port is already bound.