API authentication patterns in Svelte - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is API authentication?

API authentication is the process of verifying the identity of a user or system before allowing access to an API. It ensures only authorized users can use the API.

beginner

What is the difference between API authentication and API authorization?

Authentication checks who you are. Authorization checks what you are allowed to do after you are authenticated.

intermediate

What is a common method to authenticate API requests using tokens?

Using Bearer tokens in the Authorization header is common. The client sends a token proving identity with each request.

intermediate

How does OAuth 2.0 help with API authentication?

OAuth 2.0 lets users grant limited access to their data without sharing passwords. It uses tokens to authenticate and authorize API requests securely.

beginner

Why is it important to use HTTPS with API authentication?

HTTPS encrypts data between client and server. This protects tokens and credentials from being stolen during transmission.

Which header is commonly used to send an API token?

A Authorization

B Content-Type

C Accept

D User-Agent

The Authorization header is used to send tokens like Bearer tokens for API authentication.

What does OAuth 2.0 primarily provide?

A Token-based authentication and authorization

B Password storage

C Database encryption

D API rate limiting

OAuth 2.0 provides a secure way to authenticate and authorize API access using tokens.

Which of these is NOT a common API authentication pattern?

A API key

B Bearer token

C CSS styling

D Basic authentication

CSS styling is unrelated to API authentication.

Why should API tokens be kept secret?

A To improve API speed

B To change API endpoints

C To reduce server load

D To prevent unauthorized API access

Tokens prove identity. If leaked, attackers can access the API as the user.

What is the role of HTTPS in API authentication?

A Formats JSON data

B Encrypts data to protect credentials

C Speeds up API response

D Caches API responses

HTTPS encrypts communication, protecting tokens and credentials from interception.

Explain how token-based authentication works in APIs.

Think about how you show a ticket to enter a concert.

Describe the benefits of using OAuth 2.0 for API authentication.

Imagine giving a valet key instead of your car keys.

Practice

1. What is the main purpose of API authentication in a Svelte app?

easy

A. To verify the identity of the user or app making the request

B. To speed up the API response time

C. To change the API data format

D. To style the API response

Solution

1. Step 1: Understand API authentication role

   API authentication checks who is making the request to keep the app secure.

2. Step 2: Identify the correct purpose

   Speed, data format, and styling are unrelated to authentication.

3. Final Answer:

   To verify the identity of the user or app making the request -> Option A

4. Quick Check:

   Authentication = Verify identity [OK]

Hint: Authentication means checking who you are [OK]

Common Mistakes:

• Confusing authentication with performance optimization
• Thinking authentication changes data format
• Assuming authentication styles the response

2. Which of the following is the correct way to add a Bearer token in a fetch request header in Svelte?

easy

A. fetch(url, { headers: { 'Bearer': token } })

B. fetch(url, { headers: { 'Auth': 'Bearer ' + token } })

C. fetch(url, { headers: { 'Authorization': 'Bearer ' + token } })

D. fetch(url, { headers: { 'Authorization': token } })

Solution

1. Step 1: Recall Bearer token header format

   The standard header key is 'Authorization' with value 'Bearer ' plus the token.

2. Step 2: Match correct syntax

   fetch(url, { headers: { 'Authorization': 'Bearer ' + token } }) correctly uses 'Authorization' and concatenates 'Bearer ' with the token.

3. Final Answer:

   fetch(url, { headers: { 'Authorization': 'Bearer ' + token } }) -> Option C

4. Quick Check:

   Bearer token header = Authorization: Bearer token [OK]

Hint: Use 'Authorization' header with 'Bearer ' prefix [OK]

Common Mistakes:

• Using wrong header key like 'Auth' or 'Bearer'
• Omitting 'Bearer ' prefix before token
• Passing token without header key

3. What will be the output of this Svelte code snippet when fetching an API with Basic Auth?

const response = await fetch('https://api.example.com/data', {
  headers: {
    'Authorization': 'Basic ' + btoa('user:pass')
  }
});
const data = await response.json();
console.log(data.message);

Assuming the API returns {"message": "Success"} on correct auth.

medium

A. SyntaxError

B. Success

C. Authorization error

D. undefined

Solution

1. Step 1: Understand Basic Auth header

   The code correctly encodes 'user:pass' with btoa and sets 'Authorization' header.

2. Step 2: Predict API response

   With correct credentials, API returns JSON with message 'Success', logged to console.

3. Final Answer:

   Success -> Option B

4. Quick Check:

   Correct Basic Auth returns API success message [OK]

Hint: Basic Auth uses base64 encoded 'user:pass' in Authorization [OK]

Common Mistakes:

• Not encoding credentials with btoa
• Using wrong header key
• Expecting error without wrong credentials

4. Identify the error in this Svelte fetch call for API authentication:

fetch('https://api.example.com/data', {
  headers: {
    'Authorization': 'Bearer token123'
  }
})
.then(response => response.json())
.then(data => console.log(data));

medium

A. Missing await keyword for async fetch

B. Bearer token should be in lowercase

C. Headers object should be outside fetch options

D. No error, code is correct

Solution

1. Step 1: Check fetch usage with promises

   Using .then() is valid without await; async/await is optional here.

2. Step 2: Verify header format and placement

   'Authorization' header with 'Bearer token123' is correct and inside headers object.

3. Final Answer:

   No error, code is correct -> Option D

4. Quick Check:

   fetch with .then and correct headers = valid code [OK]

Hint: Using .then() is valid without await [OK]

Common Mistakes:

• Thinking await is mandatory with fetch
• Assuming 'Bearer' must be lowercase
• Misplacing headers outside fetch options

5. You want to securely store and use an API token in a Svelte app to authenticate requests. Which approach is best practice?

hard

A. Store the token in a Svelte writable store and include it in fetch headers

B. Hardcode the token directly in the fetch call inside the component

C. Save the token in localStorage and read it on every fetch request

D. Send the token as a URL query parameter in fetch requests

Solution

1. Step 1: Evaluate token storage options

   Writable stores in Svelte keep token in memory, safer than localStorage or hardcoding.

2. Step 2: Assess token usage in fetch

   Including token in headers from store is secure and flexible; URL query parameters expose token publicly.

3. Final Answer:

   Store the token in a Svelte writable store and include it in fetch headers -> Option A

4. Quick Check:

   Use writable store for secure token handling [OK]

Hint: Use Svelte stores, avoid hardcoding or URL tokens [OK]

Common Mistakes:

• Hardcoding tokens exposes secrets in code
• Using localStorage risks token theft via XSS
• Sending tokens in URL leaks them in logs