Supercharge Your JavaScript Skills with Fetch Requests

Table of Contents

1. Introduction
2. Placing fetch requests in an array
3. Handling multiple fetch requests with Promise.all
4. Accessing the response objects
5. Reading the Json data from each response
6. Error handling with catch
7. Using async/await for cleaner syntax
8. Avoiding nesting with async/await
9. Working with successful promises only
10. Handling failed fetch requests

Introduction

In this tutorial, we will learn how to wait for multiple fetch requests to complete before performing any action with the data. We will explore different methods such as Promise.all, async/await, and error handling techniques to efficiently handle multiple fetch requests simultaneously.

Placing fetch requests in an array

To handle multiple fetch requests together, we first need to store them in an array. Each fetch request is a promise object, and by placing them in an array, we can pass it to the Promise.all method provided by the promise object.

Handling multiple fetch requests with Promise.all

By using the Promise.all method, we can wait for all the promises (fetch requests) in the array to resolve. This method returns a new promise that resolves when all the promises in the array have resolved.

Accessing the response objects

Once the fetch requests have been resolved, we can access the response objects by using the then method. This allows us to work with the data returned by each fetch request individually.

Reading the Json data from each response

To extract the Json data from each response object, we need to Read the body of the readable stream using the json() method. However, since we have an array of response objects, we need to use the Promise.all trick again to wait for all the json() promises to resolve.

Error handling with catch

To handle errors, including those that occur during the fetch requests and the json() conversion, we can use the catch statement. By adding a catch block to the outer Promise.all, we can catch any errors and handle them accordingly.

Using async/await for cleaner syntax

Instead of using nested promises and .then syntax, we can improve the readability of the code by using the async/await syntax. By declaring the function as async and using the await keyword, we can make the code appear more synchronous and easier to read.

Avoiding nesting with async/await

By utilizing the async/await syntax, we can avoid unnecessary nesting of promises. By awaiting the result of the outer Promise.all and then using await again inside a loop to handle the json() conversion, we can achieve a cleaner and more concise code structure.

Working with successful promises only

Sometimes, we may only want to work with the promises that have resolved successfully. In such cases, we can use the Promise.allSettled method instead of Promise.all. This method returns an array of objects, each containing the status (fulfilled or rejected) and the corresponding value or reason.

Handling failed fetch requests

If we only want to handle errors when none of the fetch requests succeed, we can check the length of the success array. If the array has a length of zero, it means that none of the fetch requests were successful, and we can throw an error. By implementing this check in the catch block of Promise.allSettled, we can differentiate between complete failure and partial success.

Conclusion

In this tutorial, we have learned how to wait for multiple fetch requests to complete and handle the returned data efficiently. We explored methods like Promise.all, async/await, and error handling techniques to ensure smooth execution of multiple fetch requests. By understanding these concepts, You can improve the performance and reliability of your applications that involve multiple asynchronous requests.

Highlights

• Placing fetch requests in an array
• Handling multiple fetch requests with Promise.all
• Accessing the response objects
• Reading the Json data from each response
• Error handling with catch
• Using async/await for cleaner syntax
• Avoiding nesting with async/await
• Working with successful promises only
• Handling failed fetch requests

FAQs

Q: Can I use Promise.all to handle a single fetch request? A: Yes, you can. Promise.all is not limited to handling multiple fetch requests. It can be used to handle any number of promises, whether it's a single fetch request or multiple fetch requests.

Q: Is there a limit to the number of fetch requests I can handle with Promise.all? A: There is no specific limit imposed by Promise.all itself. However, keep in mind that handling a large number of fetch requests simultaneously may put a strain on server resources and network bandwidth. It's recommended to optimize the number of concurrent fetch requests Based on your specific use case.

Q: How can I handle different types of errors that occur during fetch requests? A: You can use the catch statement to catch and handle different types of errors. Within the catch block, you can check the error object and perform specific actions based on the error Type. For example, you can log different error messages or retry the failed fetch request.

Q: Can I abort fetch requests if they take too long to complete? A: Yes, you can abort fetch requests using the AbortController interface. By creating an instance of AbortController and passing its signal property to the signal option of the fetch request, you can programmatically abort the request using controller.abort(). This can be useful for canceling long-running requests or handling user-initiated cancellations.

Q: Are there any alternatives to using Promise.all for handling multiple fetch requests? A: Yes, besides Promise.all, you can also use other methods like Promise.race, Promise.any, or even libraries like axios or fetch-mock that provide more advanced features for managing multiple fetch requests. The choice of method or library depends on your specific requirements and project constraints.