Resource-based URL design in Express - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Express route handler?

Consider this Express route that handles a GET request for a resource by ID. What will the server respond with when a client requests /users/42?

Express

const express = require('express');
const app = express();

app.get('/users/:id', (req, res) => {
  res.send(`User ID is ${req.params.id}`);
});

// Assume server is listening

A User ID is 42

B User ID is :id

C User ID is undefined

D 404 Not Found

💡 Hint

Look at how Express uses :id in the route path and how req.params works.

The route /users/:id captures the part after /users/ as id. So when the URL is /users/42, req.params.id is 42. The response sends this value.

📝 Syntax

intermediate

Which option correctly defines a route to update a resource using PUT?

You want to create an Express route to update a book resource by its ID using the HTTP PUT method. Which code snippet correctly defines this route?

A app.delete('/books/:id', (req, res) => { res.send(`Update book ${req.params.id}`); });

B app.get('/books/:id', (req, res) => { res.send(`Update book ${req.params.id}`); });

C app.post('/books/:id', (req, res) => { res.send(`Update book ${req.params.id}`); });

D app.put('/books/:id', (req, res) => { res.send(`Update book ${req.params.id}`); });

💡 Hint

Remember that PUT is the HTTP method used for updating resources.

PUT is the standard HTTP method for updating a resource. The route /books/:id with app.put correctly matches update requests for a book by ID.

🔧 Debug

advanced

Why does this Express route not match requests as expected?

This Express app has two routes defined. Why will a GET request to /products/123 always respond with 'All products' instead of the product ID?

Express

const express = require('express');
const app = express();

app.get('/products*', (req, res) => {
  res.send('All products');
});

app.get('/products/:id', (req, res) => {
  res.send(`Product ID: ${req.params.id}`);
});

A The server is missing middleware to parse URL parameters.

B Express does not support route parameters with colons.

C The order of routes matters; the first route matches '/products' and also '/products/123' because of missing strict matching.

D The second route has a syntax error and never registers.

💡 Hint

Think about how Express matches routes in the order they are defined.

Express matches routes in the order they are defined. The first route /products* uses a wildcard that matches any path starting with /products, including /products/123. Therefore, it responds with 'All products' before the more specific /products/:id route is considered.

❓ state_output

advanced

What is the response when sending a DELETE request to this route?

Given this Express route, what will the client receive when making a DELETE request to /orders/99?

Express

const express = require('express');
const app = express();

app.delete('/orders/:orderId', (req, res) => {
  const id = req.params.orderId;
  res.status(200).json({ message: `Order ${id} deleted` });
});

A Order 99 deleted

B {"message":"Order 99 deleted"}

C {"error":"Order not found"}

D 404 Not Found

💡 Hint

Look at the response method and status code used.

The route sends a JSON response with a message confirming deletion. The status code is 200, meaning success. The response body is a JSON string with the message.

🧠 Conceptual

expert

Which URL best follows resource-based URL design principles for accessing comments of a blog post?

You have a blog post resource and each post can have multiple comments. According to resource-based URL design, which URL is the best choice to get all comments for a post with ID 7?

A /posts/7/comments

B /comments?postId=7

C /getCommentsForPost/7

D /posts/comments/7

💡 Hint

Resource-based URLs use nouns and hierarchical structure to represent relationships.

Option A uses a clear hierarchical path showing comments belong to post 7. This is the recommended RESTful style. Option A uses a query parameter which is valid but less clear about resource hierarchy. Options C and D use verbs or confusing order, which is not recommended.