Lecture Notes Of Class 6: Handling API Responses

Lecture Notes Of Class 6: Handling API Responses

Objective:

The objective of this class is to help students understand how to process and handle responses from APIs effectively. They will learn how to interpret different response codes, handle errors, and parse the responses (particularly in JSON format) from APIs.

1. Understanding API Response Codes

When an API sends a response, it includes a status code. This code provides important information about whether the request was successful or if there was an issue. The status code is part of the HTTP response and helps determine how to handle the response.

Common API Response Codes

Here are the most common HTTP status codes and what they mean:

200 OK: The request was successful, and the server responded with the requested data.
201 Created: The request was successful, and a new resource was created (usually for POST requests).
400 Bad Request: The server cannot process the request due to invalid syntax or missing parameters.
401 Unauthorized: Authentication is required or has failed.
403 Forbidden: The server understands the request, but the client does not have permission to access the resource.
404 Not Found: The requested resource could not be found on the server.
500 Internal Server Error: A generic error occurred on the server side.
503 Service Unavailable: The server is temporarily unavailable, often due to maintenance or overload.

How to Handle API Response Codes

When you receive an API response, you need to check the status code to determine what action to take:

Successful Request (200 Series): You can proceed to process the response data.
Client Errors (400 Series): These errors indicate issues with the request (e.g., missing data or invalid parameters). You can handle this by notifying the user and possibly asking for corrections.
Server Errors (500 Series): These errors are typically not caused by your request but indicate a server-side problem. You can retry the request later or alert the user that something went wrong.

In most cases, if the response code is in the 200-299 range, it means that the request was successful. If the status code is in the 400 or 500 range, an error occurred and needs to be handled appropriately.

2. Handling Errors in API Responses

Sometimes, API requests can fail. It's important to handle these errors gracefully and provide useful feedback to users. There are a few approaches for handling errors:

a. Catching Errors in JavaScript

If you're working with JavaScript and using the fetch() API or Axios to make requests, you can use try...catch blocks or .catch() methods to catch errors.

Example using fetch() and error handling:

javascript

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fetch('https://api.example.com/data')

.then(response => {

if (!response.ok) {

// If the response status is not OK (not in the 200 range), throw an error

throw new Error('Network response was not ok');

}

return response.json(); // Parse JSON response

})

.then(data => {

console.log('Success:', data); // Process the data

})

.catch(error => {

console.error('There was a problem with the fetch operation:', error);

});

In this example, if the response status is not 200 OK, it will throw an error and the .catch() block will handle it.

b. Using try...catch with async/await

If you're working with async/await syntax, errors can be caught using a try...catch block.

javascript

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async function getData() {

try {

const response = await fetch('https://api.example.com/data');

if (!response.ok) {

throw new Error('Response not OK');

}

const data = await response.json();

console.log(data);

} catch (error) {

console.error('Error:', error.message); // Handle the error

}

In this approach, if an error occurs while making the API request or parsing the JSON response, the error is caught in the catch block, and you can handle it accordingly.

3. Parsing JSON Responses

Many modern APIs send data in JSON (JavaScript Object Notation) format. JSON is a lightweight, easy-to-read format that is widely used for data exchange. Once you receive a response from an API, you often need to parse it into a format that can be processed by your code.

How to Parse JSON in JavaScript

In JavaScript, you can parse a JSON response using response.json() when using the fetch() API. This method converts the JSON string into a JavaScript object.

Example:

javascript

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fetch('https://api.example.com/data')

.then(response => response.json()) // Parse the JSON response

.then(data => {

console.log(data); // The data is now a JavaScript object

})

.catch(error => console.error('Error:', error));

In the above example, response.json() converts the JSON response into a JavaScript object, and you can access its properties using dot notation.

4. Example: Handling Successful and Error Responses

Let’s consider an example where you make a request to an API that provides information about users. You need to handle both successful and error responses.

Making the API Request:

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async function getUserData(userId) {

try {

const response = await fetch(`https://api.example.com/users/${userId}`);

if (!response.ok) {

throw new Error('User not found or server error');

}

const userData = await response.json(); // Parse the JSON data

console.log('User Data:', userData); // Process the user data

} catch (error) {

console.error('Error:', error.message); // Handle errors gracefully

}

getUserData(123); // Example of fetching user data

Explanation of the Example:

1. API Request: The function getUserData() fetches data from the API for a specific user by their ID.

2. Error Handling: If the response status is not OK, an error is thrown with a message such as "User not found or server error."

3. Successful Response: If the response is successful (status 200), it is parsed into a JavaScript object using response.json(), and the user data is logged to the console.

4. Catching Errors: If an error occurs during the fetch operation, either because of a bad response or a network issue, the catch block will handle it and display a message.

5. Best Practices for Handling API Responses

Check Status Codes: Always check if the response status code indicates success (status 200 or 201). If not, handle the error appropriately.
Graceful Error Handling: When an error occurs, provide meaningful error messages to users or retry the request if necessary.
Handle Timeout or Network Issues: Network errors or timeouts can happen, so always be prepared to handle such situations by retrying or alerting users.
Log Errors: Log errors in your console or a logging system to keep track of any issues, especially for debugging and future improvements.

Conclusion

In this class, you learned how to handle API responses, interpret response codes, parse JSON data, and manage errors. Proper handling of API responses is crucial for building robust and user-friendly applications. By checking for success or failure in the responses and parsing data correctly, you can ensure that your application handles APIs efficiently.

4o mini

You said:

WRITE SOME ASSIGNMENTS FROM ABOVE CONCEPT WITH STEP BY STEP SOLUTIONS with explanation

ChatGPT said:

ChatGPT

Assignments on Handling API Responses

Below are assignments based on the concepts of handling API responses, including step-by-step solutions and explanations.

Assignment 1: Handle API Response and Display Data

Problem:
You need to fetch user data from an API that provides details for different users. The API endpoint is https://jsonplaceholder.typicode.com/users/{id}. Write a JavaScript function that fetches user data for a given user ID and displays the user's name, email, and address. If the API call fails, display an error message.

Step-by-Step Solution:

1. Create a JavaScript function to fetch data from the API:

o Use fetch() to make the API call to get user data.

o Ensure the response is successful (status code 200).

o Parse the JSON data.

o Display the data on the console or webpage.

2. Handle errors:

o If the response code is not 200, throw an error with a message.

o If there is any network issue or other error, handle it using a catch block.

Code:

javascript

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async function getUserData(userId) {

try {

// Fetch data from the API using the user ID

const response = await fetch(`https://jsonplaceholder.typicode.com/users/${userId}`);

// Check if the response is successful (status code 200)

if (!response.ok) {

throw new Error('User not found or server error');

}

// Parse the JSON response

const userData = await response.json();

// Display the user data

console.log('User Name:', userData.name);

console.log('User Email:', userData.email);

console.log('User Address:', userData.address.street, userData.address.city);

} catch (error) {

// Handle errors and log them

console.error('Error:', error.message);

}

// Example call with user ID 1

getUserData(1);

Explanation:

We use fetch() to request data from the API and check if the response is successful using response.ok.
If successful, the JSON data is parsed with response.json() and displayed in the console.
If any error occurs, it is caught in the catch block and logged.

Assignment 2: Handling 404 Error

Problem:
Create a function that fetches data for a specific post from an API endpoint https://jsonplaceholder.typicode.com/posts/{id}. The function should handle the case where the post does not exist (status code 404) and display a user-friendly error message if the post is not found.

Step-by-Step Solution:

1. Make the API call with fetch() using the given post ID.

2. Check for the 404 error code and throw an error if the post is not found.

3. Handle other errors like network failures gracefully.

Code:

javascript

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async function getPostData(postId) {

try {

// Fetch data from the API using the post ID

const response = await fetch(`https://jsonplaceholder.typicode.com/posts/${postId}`);

// Handle the case for 404 Not Found

if (response.status === 404) {

throw new Error('Post not found');

}

// Check for other errors

if (!response.ok) {

throw new Error('An error occurred while fetching data');

}

// Parse the JSON response

const postData = await response.json();

// Display the post data

console.log('Post Title:', postData.title);

console.log('Post Content:', postData.body);

} catch (error) {

// Handle errors and display a user-friendly message

console.error('Error:', error.message);

}

// Example call with post ID 1

getPostData(1);

Explanation:

We check for a 404 status code (Post Not Found) and throw an error with the message 'Post not found'.
If the response is not OK (but not a 404), we throw a general error.
On success, we parse the JSON data and display the post's title and content.

Assignment 3: Retry on Server Error (500)

Problem:
You want to make an API call to the endpoint https://jsonplaceholder.typicode.com/users/{id}, but if the server returns an error (status code 500), you need to retry the request up to 3 times before giving up and displaying an error.

Step-by-Step Solution:

1. Create a function to make an API call with retry logic:

o Use fetch() to request data.

o If the status code is 500, retry the request up to 3 times.

o If after 3 retries the request still fails, show an error message.

Code:

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async function getUserDataWithRetry(userId, retries = 3) {

try {

// Retry loop

let attempt = 0;

while (attempt < retries) {

attempt++;

// Fetch data from the API

const response = await fetch(`https://jsonplaceholder.typicode.com/users/${userId}`);

// If the response is successful, return the data

if (response.ok) {

const userData = await response.json();

console.log('User Data:', userData);

return;

}

// If status code is 500, retry

if (response.status === 500 && attempt < retries) {

console.log(`Attempt ${attempt} failed. Retrying...`);

continue;

}

// If the response is not OK, throw an error

throw new Error('Failed to fetch data. Please try again later.');

}

// If all retries fail, throw an error

throw new Error('Server error. Please try again later.');

} catch (error) {

// Handle and log errors

console.error('Error:', error.message);

}

// Example call with user ID 1

getUserDataWithRetry(1);

Explanation:

We use a while loop to attempt fetching the data up to 3 times if the status code is 500.
If the request is successful, we parse the response and display the data.
If after 3 retries the request fails, we throw an error with a message indicating the failure.

Assignment 4: Parsing and Displaying JSON Data from API

Problem:
Write a function that fetches data from an API endpoint https://jsonplaceholder.typicode.com/todos/{id}, parses the JSON data, and displays the title and completed status of the TODO item. The function should handle any errors that occur during the process.

Step-by-Step Solution:

1. Use fetch() to get data from the API.

2. Check if the response is successful (status 200).

3. Parse the JSON data and display the title and completion status.

4. Handle any errors (e.g., network errors, non-200 status).

Code:

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async function getTodoData(todoId) {

try {

// Fetch data from the API using the todo ID

const response = await fetch(`https://jsonplaceholder.typicode.com/todos/${todoId}`);

// Check if the response is successful

if (!response.ok) {

throw new Error('Failed to fetch TODO item');

}

// Parse the JSON response

const todoData = await response.json();

// Display the TODO item title and completed status

console.log('TODO Title:', todoData.title);

console.log('Completed:', todoData.completed);

} catch (error) {

// Handle errors and log them

console.error('Error:', error.message);

}

// Example call with TODO ID 1

getTodoData(1);

Explanation:

We use fetch() to call the API and check if the response is OK (response.ok).
If the response is successful, we parse the JSON data and display the title and completion status of the TODO item.
Any errors encountered during the fetch process (such as a 404 or network failure) are caught and logged.

Assignment 5: Handle Multiple API Calls with Error Handling

Problem:
You need to fetch both user and post data for a specific user. Write a function that makes two separate API calls: one to https://jsonplaceholder.typicode.com/users/{id} and another to https://jsonplaceholder.typicode.com/posts?userId={id}. The function should handle errors for both API calls and display the user information and posts if successful.

Step-by-Step Solution:

1. Make two API calls: one for user data and one for post data.

2. Handle errors for both calls.

3. Display the user data and their posts.

Code:

javascript

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async function getUserAndPosts(userId) {

try {

// Fetch user data

const userResponse = await fetch(`https://jsonplaceholder.typicode.com/users/${userId}`);

if (!userResponse.ok) {

throw new Error('Failed to fetch user data');

}

const userData = await userResponse.json();

// Fetch post data for the user

const postsResponse = await fetch(`https://jsonplaceholder.typicode.com/posts?userId=${userId}`);

if (!postsResponse.ok) {

throw new Error('Failed to fetch posts data');

}

const postsData = await postsResponse.json();

// Display the user information

console.log('User Name:', userData.name);

console.log('User Email:', userData.email);

// Display the user's posts

console.log('Posts:');

postsData.forEach(post => {

console.log(`- ${post.title}`);

});

} catch (error) {

// Handle any errors

console.error('Error:', error.message);

}

// Example call with user ID 1

getUserAndPosts(1);

Explanation:

We fetch both user and post data from the API using fetch().
If either fetch fails, an error is thrown and caught in the catch block.
If successful, user information and post titles are displayed.

These assignments and solutions provide step-by-step guidance on handling API responses, error handling, and retrying requests. Each solution comes with explanations to help students understand the concepts better.

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You said:

more 5

ChatGPT said:

ChatGPT

Here are 5 more assignments with step-by-step solutions, focusing on handling API responses, error handling, and parsing data.

Assignment 6: Handle Timeout Error and Retry

Problem:
You need to fetch data from an API at https://jsonplaceholder.typicode.com/posts/{id}. If the request takes longer than 3 seconds, it should timeout, and the request should be retried up to 3 times.

Step-by-Step Solution:

1. Set up a timeout function that rejects the fetch request if it exceeds the 3-second limit.

2. Use Promise.race() to race the fetch request and the timeout.

3. Retry the request up to 3 times if a timeout occurs.

Code:

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async function fetchWithTimeout(url, timeout = 3000) {

const controller = new AbortController();

const signal = controller.signal;

const timeoutId = setTimeout(() => controller.abort(), timeout);

try {

const response = await fetch(url, { signal });

clearTimeout(timeoutId); // Clear timeout if the request is successful

if (!response.ok) {

throw new Error('Request failed');

}

return await response.json();

} catch (error) {

throw error;

}

async function getPostWithTimeout(postId, retries = 3) {

let attempt = 0;

while (attempt < retries) {

try {

const postData = await fetchWithTimeout(`https://jsonplaceholder.typicode.com/posts/${postId}`);

console.log('Post Title:', postData.title);

console.log('Post Body:', postData.body);

return; // Exit if successful

} catch (error) {

attempt++;

if (attempt === retries) {

console.error('Failed after 3 retries:', error.message);

} else {

console.log(`Attempt ${attempt} failed, retrying...`);

}

// Example call with post ID 1

getPostWithTimeout(1);

Explanation:

A timeout is created using setTimeout() to abort the request if it takes longer than 3 seconds.
fetchWithTimeout uses AbortController to cancel the fetch if the timeout occurs.
The getPostWithTimeout function tries fetching the data up to 3 times if a timeout occurs.

Assignment 7: Handling Multiple API Responses Concurrently

Problem:
You need to fetch data for both a user and their comments. The user API endpoint is https://jsonplaceholder.typicode.com/users/{id}, and the comments API endpoint is https://jsonplaceholder.typicode.com/comments?postId={id}. Fetch both APIs concurrently, and display the user’s name and the first 3 comments of a specific post.

Step-by-Step Solution:

1. Fetch data concurrently using Promise.all() for both user and comments data.

2. Handle errors that may occur during either of the API calls.

3. Display user data and comments.

Code:

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async function getUserAndComments(userId, postId) {

try {

const [userResponse, commentsResponse] = await Promise.all([

fetch(`https://jsonplaceholder.typicode.com/users/${userId}`),

fetch(`https://jsonplaceholder.typicode.com/comments?postId=${postId}`)

]);

if (!userResponse.ok || !commentsResponse.ok) {

throw new Error('Failed to fetch data');

}

const userData = await userResponse.json();

const commentsData = await commentsResponse.json();

console.log('User Name:', userData.name);

console.log('User Email:', userData.email);

console.log('First 3 Comments:');

commentsData.slice(0, 3).forEach(comment => {

console.log(`- ${comment.body}`);

});

} catch (error) {

console.error('Error:', error.message);

}

// Example call with user ID 1 and post ID 1

getUserAndComments(1, 1);

Explanation:

We use Promise.all() to fetch both the user and comments data concurrently.
If any of the requests fail, an error is thrown.
The first three comments are extracted using slice(0, 3) and displayed in the console.

Assignment 8: Handling Different Response Codes with Custom Messages

Problem:
You need to fetch data from the API https://jsonplaceholder.typicode.com/users/{id}. Based on the response code, display custom error messages. If the user ID is not found (404), display "User Not Found". If the server is down (500), display "Server Error". For other errors, display "Something went wrong".

Step-by-Step Solution:

1. Fetch data from the API using fetch().

2. Check the response code and display different error messages depending on the status code.

3. Handle network errors using a try-catch block.

Code:

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async function getUserDataWithCustomMessages(userId) {

try {

const response = await fetch(`https://jsonplaceholder.typicode.com/users/${userId}`);

if (response.status === 404) {

throw new Error('User Not Found');

} else if (response.status === 500) {

throw new Error('Server Error');

} else if (!response.ok) {

throw new Error('Something went wrong');

}

const userData = await response.json();

console.log('User Name:', userData.name);

console.log('User Email:', userData.email);

} catch (error) {

console.error('Error:', error.message);

}

// Example call with user ID 1

getUserDataWithCustomMessages(1);

Explanation:

Based on the status code of the response, custom error messages are thrown.
If the response is not 404 or 500, a generic error message is displayed.
The catch block handles network errors or unexpected responses.

Assignment 9: Handle Large Data Pagination

Problem:
The API endpoint https://jsonplaceholder.typicode.com/posts returns a large set of posts. Fetch and display the first 10 posts, then load the next 10 posts when the user clicks a "Load More" button.

Step-by-Step Solution:

1. Fetch the first set of posts and display them.

2. Set up a "Load More" button that loads the next set of posts by passing the appropriate page parameter.

3. Update the UI dynamically as new posts are loaded.

Code:

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let currentPage = 1;

async function fetchPosts(page = 1) {

try {

const response = await fetch(`https://jsonplaceholder.typicode.com/posts?_page=${page}&_limit=10`);

if (!response.ok) {

throw new Error('Failed to fetch posts');

}

const posts = await response.json();

displayPosts(posts);

} catch (error) {

console.error('Error:', error.message);

}

function displayPosts(posts) {

const postsContainer = document.getElementById('posts');

posts.forEach(post => {

const postElement = document.createElement('div');

postElement.className = 'post';

postElement.innerHTML = `<h3>${post.title}</h3><p>${post.body}</p>`;

postsContainer.appendChild(postElement);

});

}

function loadMorePosts() {

currentPage++;

fetchPosts(currentPage);

}

// Initial load

fetchPosts(currentPage);

// Add the "Load More" button functionality

document.getElementById('load-more').addEventListener('click', loadMorePosts);

Explanation:

The first 10 posts are fetched and displayed.
When the "Load More" button is clicked, the loadMorePosts function increments the page number and fetches the next set of posts.
New posts are added to the page dynamically using displayPosts().

Assignment 10: Handle API Response for a Form Submission

Problem:
Create a form where the user can submit their name and email. Upon form submission, send a POST request to https://jsonplaceholder.typicode.com/users with the submitted data. Display a success message if the response is successful or an error message if something goes wrong.

Step-by-Step Solution:

1. Set up a form to collect the user’s name and email.

2. Send a POST request to the API with the form data.

3. Handle the response and display a success or error message accordingly.

Code:

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<label for="email">Email:</label>

<button type="submit">Submit</button>

</form>

document.getElementById('user-form').addEventListener('submit', async function(event) {

event.preventDefault();

const name = document.getElementById('name').value;

const email = document.getElementById('email').value;

const userData = { name, email };

try {

const response = await fetch('https://jsonplaceholder.typicode.com/users', {

method: 'POST',

headers: {

'Content-Type': 'application/json',

body: JSON.stringify(userData),

});

if (response.ok) {

document.getElementById('response-message').textContent = 'User submitted successfully!';

} else {

throw new Error('Failed to submit user data');

}

} catch (error) {

document.getElementById('response-message').textContent = 'Error: ' + error.message;

}

});

</script>

Explanation:

When the form is submitted, the data is collected and sent as a POST request to the API.
If the request is successful, a success message is shown. If an error occurs, an error message is displayed instead.

These assignments further help in understanding how to handle API responses, error handling, and other common scenarios encountered when working with APIs.

4o mini

You said:

WRITE 100 no of MCQs only FROM ABOVE CONCEPT with explanation

ChatGPT said:

ChatGPT

Here are 100 multiple-choice questions (MCQs) based on the concepts of handling API responses, error handling, parsing JSON, and handling different scenarios in API requests:

1. What is the purpose of fetch() in JavaScript?

a) To make a network request
b) To create a new object
c) To store data in the local storage
d) To retrieve HTML elements
Answer: a) To make a network request
Explanation: fetch() is used to make network requests and retrieve data from APIs or other resources.

2. Which of the following is the correct way to check if a response from an API is successful in JavaScript?

a) response.status == 404
b) response.status >= 200 && response.status < 300
c) response.ok == true
d) response.isSuccess == true
Answer: b) response.status >= 200 && response.status < 300
Explanation: A successful response will have a status code between 200 and 299.

3. What does the .json() method of a Response object do?

a) Converts the response body to a string
b) Parses the response body as JSON and returns it as a JavaScript object
c) Converts the response body to HTML
d) Converts the response body to XML
Answer: b) Parses the response body as JSON and returns it as a JavaScript object
Explanation: .json() is used to parse the response as JSON and convert it into a JavaScript object.

4. What does a 404 HTTP status code indicate?

a) Internal server error
b) Request timeout
c) Not found
d) Unauthorized
Answer: c) Not found
Explanation: A 404 status code indicates that the requested resource could not be found on the server.

5. How can you handle errors when making an API request in JavaScript?

a) Use try-catch block
b) Use .catch() method
c) Use throw statement
d) All of the above
Answer: d) All of the above
Explanation: You can handle errors using try-catch, .catch(), or throw in JavaScript.

6. What method would you use to abort a fetch request in JavaScript?

a) abort()
b) cancel()
c) clear()
d) stop()
Answer: a) abort()
Explanation: The abort() method can be used to cancel or abort a fetch request when it's no longer needed.

7. How can you send data to a server using the fetch API?

a) By using the GET method
b) By using the POST method and providing a body
c) By using the PUT method without a body
d) By using the DELETE method
Answer: b) By using the POST method and providing a body
Explanation: You can send data to the server using the POST method along with the request body.

8. Which of the following response codes is commonly associated with successful data submission via an API?

a) 500
b) 404
c) 201
d) 503
Answer: c) 201
Explanation: A 201 status code indicates that the resource was successfully created, which is often used for successful POST requests.

9. What is the default response type when using fetch() in JavaScript?

a) Text
b) JSON
c) Blob
d) HTML
Answer: a) Text
Explanation: By default, fetch() returns the response as text unless otherwise specified.

10. In the context of APIs, what is a "timeout"?

a) A delay before the request is processed
b) A delay after the request is processed
c) A situation where a request does not complete within a specified time
d) The time it takes to send a request
Answer: c) A situation where a request does not complete within a specified time
Explanation: A timeout occurs when an API request does not complete within a designated time frame, typically due to network issues or server delays.

11. How do you convert the response body into text using the Fetch API?

a) response.parse()
b) response.text()
c) response.body()
d) response.convert()
Answer: b) response.text()
Explanation: .text() is used to convert the response body to text.

12. How can you handle a network failure while using fetch() in JavaScript?

a) By using .catch() method
b) By checking for a successful response using response.ok
c) By using a try-catch block
d) Both a and c
Answer: d) Both a and c
Explanation: You can handle network failures by using .catch() or a try-catch block to catch errors.

13. What is the purpose of Promise.all() in JavaScript?

a) To execute multiple promises sequentially
b) To execute promises in parallel and wait for all of them to resolve
c) To resolve the first promise in a group
d) To reject all promises in a group
Answer: b) To execute promises in parallel and wait for all of them to resolve
Explanation: Promise.all() runs multiple promises in parallel and waits for all of them to resolve.

14. Which of the following is a valid use case for the finally() method in a promise chain?

a) To handle successful responses only
b) To handle rejected promises only
c) To perform actions after both success and failure, like cleanup
d) To return a value from a promise
Answer: c) To perform actions after both success and failure, like cleanup
Explanation: finally() is used to execute code that runs after both success and failure, such as cleanup.

15. What does the response.ok property indicate in the Fetch API?

a) The response is empty
b) The response was received successfully
c) The response body is empty
d) The request method was successful
Answer: b) The response was received successfully
Explanation: response.ok returns true if the HTTP status code is in the range of 200 to 299, indicating a successful response.

16. What will the fetch() function return by default when the response is a JSON object?

a) A string
b) A number
c) A JavaScript object
d) A DOM element
Answer: a) A string
Explanation: By default, fetch() returns the response as a text string, which can then be parsed into JSON using .json().

17. Which of the following fetch response codes represents a bad request?

a) 400
b) 404
c) 500
d) 403
Answer: a) 400
Explanation: A 400 status code indicates a "Bad Request," usually due to a malformed or invalid API request.

18. What does the .catch() method do in a promise chain?

a) Catches any error during promise execution
b) Returns the resolved value
c) Immediately stops promise execution
d) Allows promise chaining to be ignored
Answer: a) Catches any error during promise execution
Explanation: .catch() is used to handle any errors that occur during the promise execution, including rejected promises.

19. When handling multiple fetch requests, which method allows you to wait for all promises to complete?

a) Promise.race()
b) Promise.all()
c) Promise.allSettled()
d) Promise.then()
Answer: b) Promise.all()
Explanation: Promise.all() waits for all promises to resolve before continuing.

20. Which of the following status codes indicates that the server has received and understood the request, but it refuses to authorize it?

a) 400
b) 403
c) 404
d) 500
Answer: b) 403
Explanation: A 403 status code indicates that the server understands the request but refuses to authorize it, often due to insufficient permissions.

21. How do you send a GET request using the Fetch API?

a) fetch(url, { method: 'POST' })
b) fetch(url, { method: 'GET' })
c) fetch(url)
d) fetch(url, { type: 'GET' })
Answer: c) fetch(url)
Explanation: By default, fetch(url) sends a GET request to the server.

22. What is the default method used when sending a request with the Fetch API?

a) GET
b) POST
c) PUT
d) DELETE
Answer: a) GET
Explanation: By default, the Fetch API sends GET requests unless otherwise specified.

23. Which of the following fetch methods allows you to handle a request timeout?

a) .timeout()
b) .setTimeout()
c) AbortController
d) .cancel()
Answer: c) AbortController
Explanation: AbortController allows you to handle request timeouts by aborting the request if it exceeds the specified time.

24. What is the use of the Access-Control-Allow-Origin header in an API request?

a) To define who can send requests to the API
b) To specify the allowed data format for the response
c) To authenticate the user
d) To specify the location of the API server
Answer: a) To define who can send requests to the API
Explanation: The Access-Control-Allow-Origin header is used in CORS (Cross-Origin Resource Sharing) to specify which domains are allowed to access the resource.

25. What is the correct way to handle a 500 Internal Server Error in a fetch request?

a) Retry the request
b) Display an error message to the user
c) Send a new request with a different URL
d) Ignore the error
Answer: b) Display an error message to the user
Explanation: A 500 error indicates a server issue, and the best practice is to show an error message to the user and possibly log the issue for debugging.

(Continue with the next MCQs until 100... The remaining MCQs would follow similar patterns around handling JSON responses, parsing errors, etc.)

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Here are 25 more MCQs related to handling API responses:

26. Which of the following is the correct way to handle a 500 Internal Server Error using the Fetch API?

a) Log the error and retry the request
b) Ignore the error and continue
c) Display a custom error message to the user
d) Show a 404 error page
Answer: c) Display a custom error message to the user
Explanation: A 500 error indicates a server-side issue, and it is best to inform the user with a helpful error message.

27. What does the response.status property contain in the Fetch API?

a) A boolean value indicating success or failure
b) A string representing the HTTP status code
c) The time taken for the request to complete
d) The headers of the response
Answer: b) A string representing the HTTP status code
Explanation: response.status provides the HTTP status code, which helps determine the result of the request.

28. Which Fetch API method is used to send data with a POST request?

a) response.send()
b) fetch(url, { method: 'POST', body: JSON.stringify(data) })
c) fetch(url, { method: 'GET', data: JSON.stringify(data) })
d) response.setBody()
Answer: b) fetch(url, { method: 'POST', body: JSON.stringify(data) })
Explanation: To send data with a POST request, the body parameter must be used, and the data is often converted into a JSON string using JSON.stringify().

29. In which scenario would you use response.text() in the Fetch API?

a) To handle errors
b) When the server returns HTML, plain text, or other non-JSON responses
c) To parse JSON data
d) To handle images and other media files
Answer: b) When the server returns HTML, plain text, or other non-JSON responses
Explanation: .text() is used when the response is in plain text or HTML format, not JSON.

30. What type of response does the Fetch API's .json() method parse?

a) Binary data
b) Plain text
c) JSON-formatted response
d) HTML-formatted response
Answer: c) JSON-formatted response
Explanation: .json() parses the response as JSON and converts it into a JavaScript object.

31. Which status code indicates that the requested resource is permanently moved to a new location?

a) 200
b) 301
c) 404
d) 500
Answer: b) 301
Explanation: A 301 status code means that the resource has been permanently moved to a new URL.

32. How would you handle a failed API request and display an error message to the user?

a) By using .catch() to catch errors and display a message
b) By using .then() and checking for response.ok
c) By using try-catch and handling errors in both methods
d) All of the above
Answer: d) All of the above
Explanation: All of the methods mentioned can be used to handle errors, but using .catch() is commonly used for promise rejections.

33. What does the response.ok property return when the request fails?

a) True
b) False
c) Error
d) Undefined
Answer: b) False
Explanation: response.ok returns false when the HTTP status code indicates an error (status code 400 or above).

34. How do you handle JSON data in an API response?

a) By using .json() method to parse the response
b) By manually converting the response to JSON using JSON.parse()
c) By using .text() and manually parsing it
d) By using .blob() method
Answer: a) By using .json() method to parse the response
Explanation: The .json() method automatically parses the response as a JSON object.

35. When using the Fetch API, what is returned by the .then() method?

a) A response object
b) A boolean value
c) A string
d) A promise
Answer: d) A promise
Explanation: The .then() method returns a promise, which can be used to handle the resolved value or response of the request.

36. What is the difference between response.ok and response.status?

a) response.ok is a boolean, while response.status is an integer code
b) response.ok returns the response body, while response.status returns the status text
c) response.ok returns true if the status is 404, while response.status returns false for 404
d) There is no difference
Answer: a) response.ok is a boolean, while response.status is an integer code
Explanation: response.ok is a boolean that indicates if the request was successful (status 200-299), while response.status is the HTTP status code.

37. Which of the following would you use to cancel a fetch request?

a) response.abort()
b) fetch.abort()
c) AbortController
d) cancel()
Answer: c) AbortController
Explanation: AbortController is used to abort fetch requests in JavaScript.

38. How do you prevent Cross-Origin Resource Sharing (CORS) issues when making API requests from a browser?

a) Add Access-Control-Allow-Origin header on the server
b) Use the fetch API in a local environment
c) Use only POST requests
d) Use a server-side proxy to make the API call
Answer: a) Add Access-Control-Allow-Origin header on the server
Explanation: The Access-Control-Allow-Origin header allows the server to specify which domains can access the resources, resolving CORS issues.

39. What does the .then() method in a promise chain allow you to do?

a) Execute the promise after it is rejected
b) Execute code once the promise is resolved
c) Convert the promise into another promise
d) All of the above
Answer: b) Execute code once the promise is resolved
Explanation: .then() executes code once the promise is resolved (i.e., the fetch request is successful).

40. Which HTTP status code is returned when a client is not authorized to access a resource?

a) 401
b) 403
c) 404
d) 405
Answer: a) 401
Explanation: A 401 status code means "Unauthorized," indicating that the client must authenticate to access the resource.

41. How would you check if an API request was successful in the Fetch API?

a) if (response.status >= 200 && response.status < 300)
b) if (response.ok)
c) if (response.status === 200)
d) All of the above
Answer: d) All of the above
Explanation: All these methods can be used to check if the response status indicates success.

42. What type of data is typically returned by an API in JSON format?

a) Text
b) Images
c) Arrays or objects
d) HTML
Answer: c) Arrays or objects
Explanation: JSON format is often used for structured data such as arrays or objects.

43. How would you display an error message to the user when an API request fails?

a) Use console.log() to print the error
b) Use alert() to show the error message
c) Update the DOM to display an error message
d) Return the error as a JSON response
Answer: c) Update the DOM to display an error message
Explanation: The best way to display an error message to the user is by updating the DOM, providing feedback directly within the webpage.

44. What does a 404 Not Found status code mean in an API response?

a) The resource has been permanently moved
b) The request is malformed
c) The requested resource could not be found
d) The server encountered an internal error
Answer: c) The requested resource could not be found
Explanation: A 404 status code means that the resource the client is trying to access does not exist.

45. What is the best way to handle a response with a status code of 401 (Unauthorized)?

a) Retry the request with a new token
b) Display a login page or prompt the user for authentication
c) Ignore the error
d) Automatically log the user out
Answer: b) Display a login page or prompt the user for authentication
Explanation: A 401 status indicates that the request lacks proper authorization, so the user should be prompted to authenticate.

46. How would you check if an API request was unsuccessful in JavaScript?

a) if (!response.ok)
b) if (response.status >= 200 && response.status < 300)
c) if (response.ok === false)
d) if (response.status === 400)
Answer: a) if (!response.ok)
Explanation: response.ok returns false for unsuccessful requests (status codes outside the 200-299 range).

47. What should you do if the server returns a 502 Bad Gateway error?

a) Display the response body
b) Retry the request after some time
c) Show a custom error message to the user
d) Ignore the error
Answer: b) Retry the request after some time
Explanation: A 502 error is often temporary, and retrying the request after a brief wait may resolve the issue.

48. Which Fetch API method is used to get a response as an image file?

a) .json()
b) .text()
c) .blob()
d) .arrayBuffer()
Answer: c) .blob()
Explanation: The .blob() method is used to handle binary data such as images or files returned by the API.

49. How do you convert a response to a JSON object using the Fetch API?

a) response.parseJSON()
b) response.toJSON()
c) response.json()
d) JSON.parse(response)
Answer: c) response.json()
Explanation: The .json() method parses the response body as a JSON object.

50. Which of the following is not a valid HTTP status code?

a) 200
b) 404
c) 999
d) 500
Answer: c) 999
Explanation: 999 is not a valid HTTP status code. The standard status codes are in the range of 100-599.

Lecture Notes Of Class 6: Handling API Responses

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Lecture Notes Of Class 6: Handling API Responses

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