Resource-based URL design in Express - Mini Project: Build & Apply

Resource-based URL Design with Express

📖 Scenario: You are building a simple web server for a library. The server will manage books and authors using resource-based URLs.

🎯 Goal: Create an Express server with routes that follow resource-based URL design principles for books and authors.

📋 What You'll Learn

Create an Express app instance called app

Define a route to get all books at /books

Define a route to get a single book by id at /books/:id

Define a route to get all authors at /authors

Define a route to get a single author by id at /authors/:id

💡 Why This Matters

🌍 Real World

Web servers often use resource-based URLs to organize data access clearly and predictably, like accessing books or authors by their IDs.

💼 Career

Understanding resource-based URL design and Express routing is essential for backend web development roles.

1

Set up Express app

Create a variable called express by requiring the 'express' module. Then create an Express app instance called app by calling express().

Express

const express = require('express');
// Your code here

Hint

Use require('express') to import Express and then call it to create the app.

2

Add configuration for port

Create a constant called PORT and set it to 3000.

Express

const express = require('express');
const app = express();
// Your code here

Hint

Use const PORT = 3000; to set the port number.

3

Define resource-based routes

Add four routes to the app:

• GET /books that sends 'List of books'
• GET /books/:id that sends 'Book details for id: ' plus the id parameter
• GET /authors that sends 'List of authors'
• GET /authors/:id that sends 'Author details for id: ' plus the id parameter

Express

const express = require('express');
const app = express();
const PORT = 3000;
// Your code here

Hint

Use app.get with the exact URL paths and send the specified text responses.

4

Start the server

Add code to start the server by calling app.listen with PORT and a callback that sends 'Server running on port ' plus the PORT.

Express

const express = require('express');
const app = express();
const PORT = 3000;

app.get('/books', (req, res) => {
  res.send('List of books');
});

app.get('/books/:id', (req, res) => {
  res.send(`Book details for id: ${req.params.id}`);
});

app.get('/authors', (req, res) => {
  res.send('List of authors');
});

app.get('/authors/:id', (req, res) => {
  res.send(`Author details for id: ${req.params.id}`);
});
// Your code here

Hint

Use app.listen(PORT, () => { ... }) to start the server and log the message.

Practice

1. What is the main idea behind resource-based URL design in Express?

easy

A. Combine all actions into one URL

B. Use random URLs for each action

C. Avoid using HTTP methods in URLs

D. Organize URLs around data items like users or books

Solution

1. Step 1: Understand resource-based URL design

   This design organizes URLs by resources such as users or books, making them clear and meaningful.

2. Step 2: Compare options

   Options B, C, and D do not follow this clear organization principle.

3. Final Answer:

   Organize URLs around data items like users or books -> Option D

4. Quick Check:

   Resource-based URLs = Organize by data items [OK]

Hint: Think: URLs should name data items clearly [OK]

Common Mistakes:

• Thinking URLs should be random or unclear
• Ignoring HTTP methods in design
• Putting all actions under one URL

2. Which Express route correctly follows resource-based URL design to get a user by ID?

easy

A. app.get('/user/:id', handler)

B. app.get('/getUser', handler)

C. app.post('/user/:id', handler)

D. app.delete('/user', handler)

Solution

1. Step 1: Identify correct HTTP method and URL pattern

   To get a user by ID, use GET method and URL with resource and ID: '/user/:id'.

2. Step 2: Check options

   app.get('/user/:id', handler) uses GET and '/user/:id' which is correct. Others use wrong methods or URLs.

3. Final Answer:

   app.get('/user/:id', handler) -> Option A

4. Quick Check:

   GET + /resource/:id = correct get route [OK]

Hint: GET method + resource path with :id for fetching [OK]

Common Mistakes:

• Using POST instead of GET for fetching
• Using generic paths like '/getUser'
• Missing :id parameter in URL

3. What will be the response if the following Express route is called with DELETE /books/123?

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

medium

A. 404 Not Found error

B. "Deleted book :bookId"

C. "Deleted book 123"

D. SyntaxError

Solution

1. Step 1: Understand route and HTTP method

   The route listens for DELETE requests on '/books/:bookId'. The parameter bookId will be '123' from the URL.

2. Step 2: Check response behavior

   The handler sends a string with the bookId inserted, so response is 'Deleted book 123'.

3. Final Answer:

   "Deleted book 123" -> Option C

4. Quick Check:

   DELETE /books/:id returns message with id [OK]

Hint: Route param replaces :bookId in response [OK]

Common Mistakes:

• Confusing parameter name with literal string
• Expecting 404 if route exists
• Thinking syntax error occurs

4. Identify the error in this Express route for updating a user:

app.put('/users', (req, res) => {
  const id = req.params.id;
  res.send(`Updated user ${id}`);
});

medium

A. req.params.id should be req.body.id

B. Missing :id parameter in URL path

C. res.send should be res.json

D. Using PUT instead of POST

Solution

1. Step 1: Check URL path and parameter usage

   The route URL is '/users' but code tries to read req.params.id which requires ':id' in path.

2. Step 2: Identify mismatch

   Since ':id' is missing in URL, req.params.id will be undefined causing error or wrong behavior.

3. Final Answer:

   Missing :id parameter in URL path -> Option B

4. Quick Check:

   URL must include :id to access req.params.id [OK]

Hint: Check if URL path matches params used in code [OK]

Common Mistakes:

• Ignoring missing :id in URL
• Confusing req.params with req.body
• Thinking PUT is wrong method here

5. You want to design Express routes for a blog API with posts and comments. Which URL design best follows resource-based principles for updating a comment with ID 45 on post with ID 10?

hard

A. app.put('/posts/10/comments/45', handler)

B. app.put('/updateComment', handler)

C. app.put('/comments/45', handler)

D. app.put('/posts/comments', handler)

Solution

1. Step 1: Understand nested resource URLs

   Comments belong to posts, so URL should reflect this hierarchy: '/posts/:postId/comments/:commentId'.

2. Step 2: Check options for correct pattern

   app.put('/posts/10/comments/45', handler) uses full nested path with IDs, matching resource-based design. Others miss nesting or IDs.

3. Final Answer:

   app.put('/posts/10/comments/45', handler) -> Option A

4. Quick Check:

   Nested resource URLs = /posts/:postId/comments/:commentId [OK]

Hint: Nest related resources in URL with IDs [OK]

Common Mistakes:

• Using generic action names in URL
• Omitting parent resource ID
• Ignoring resource hierarchy