express.static middleware - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does express.static middleware do in this code?

Consider this Express.js code snippet:

const express = require('express');
const app = express();
app.use(express.static('public'));
app.listen(3000);

What will happen when a user visits http://localhost:3000/image.png assuming public/image.png exists?

Express

const express = require('express');
const app = express();
app.use(express.static('public'));
app.listen(3000);

A The server will return a 404 error because no route is defined for '/image.png'.

B The server will send the file 'public/image.png' to the user.

C The server will redirect the user to '/public/image.png'.

D The server will respond with a JSON listing of files in the 'public' folder.

💡 Hint

Think about what express.static middleware does with file paths matching the URL.

The express.static middleware serves static files from the specified folder. When the URL matches a file in 'public', it sends that file directly.

📝 Syntax

intermediate

Which option correctly uses express.static to serve files from 'assets' folder?

Choose the correct way to use express.static middleware to serve files from a folder named 'assets'.

A app.use(express.static('assets'));

B app.use(express.static('/assets'));

C app.use(express.static('./assets'));

D app.use(express.static('assets/'));

💡 Hint

Consider how express.static expects the folder path relative to the project root.

The argument to express.static is a string path relative to the current working directory. 'assets' is correct. Adding slashes or dots can cause errors or unexpected behavior.

🔧 Debug

advanced

Why does this express.static middleware not serve files as expected?

Look at this code:

const express = require('express');
const app = express();
app.use('/static', express.static('public'));
app.listen(3000);

When visiting http://localhost:3000/image.png, the file does not load. Why?

A Because the URL must start with '/static' to serve files from 'public'.

B Because the folder 'public' does not exist.

C Because the server is not listening on port 3000.

D Because express.static cannot be used with a path prefix.

💡 Hint

Check the URL path and the mount path of the middleware.

When express.static is mounted at '/static', files inside 'public' are served only when the URL starts with '/static'. So /image.png won't work, but /static/image.png will.

❓ state_output

advanced

What is the output when accessing a missing file with express.static?

Given this Express app:

const express = require('express');
const app = express();
app.use(express.static('public'));
app.listen(3000);

What happens when a user requests http://localhost:3000/missing.txt if missing.txt does not exist in 'public'?

A The server redirects to the root URL '/'.

B The server responds with a 500 Internal Server Error.

C The server responds with an empty 200 OK response.

D The server responds with a 404 Not Found error.

💡 Hint

Think about how express.static handles requests for files that are not found.

If the requested file is not found, express.static automatically sends a 404 Not Found response.

🧠 Conceptual

expert

How does express.static middleware affect the request lifecycle in Express?

Which statement best describes how express.static middleware interacts with other middleware and routes in an Express app?

A express.static modifies the request object to include file metadata but does not send responses.

B express.static only works if placed after all route handlers in the middleware stack.

C express.static handles matching requests and ends the response, preventing later middleware or routes from running for those requests.

D express.static always passes control to the next middleware regardless of whether it serves a file.

💡 Hint

Consider what happens when express.static finds a matching file to serve.

When express.static finds a file matching the request URL, it sends the file and ends the response. This means no later middleware or routes run for that request.