Скачать или смотреть Fixing the Undefined Response Issue in Fetch Requests in React

Learn how to properly handle HTTP fetch requests in React and ensure you receive expected responses from your server.
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This video is based on the question https://stackoverflow.com/q/73321574/ asked by the user 'infinitezero' ( https://stackoverflow.com/u/5436259/ ) and on the answer https://stackoverflow.com/a/73322757/ provided by the user 'sms' ( https://stackoverflow.com/u/16835747/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Tackling the Undefined Response Issue in HTTP Fetch Requests in React

If you're venturing into the world of React and making HTTP requests, you may run into a frustrating problem: receiving an undefined response from your fetch call, even when you get a successful status code of 200. This guide will unravel this issue and provide a clear solution to ensure you see the desired output, such as "Hello World" from your PHP script.

Understanding the Problem

You're sending a POST request to your local Apache server, expecting to retrieve text data. Your PHP script is configured to write "Hello World" into a text file and echo it back. However, when you fetch that response, the console logs [undefined], which indicates that something is going wrong in the way you are handling the response in JavaScript.

Key Components of the Problem:

Request to Local Server: Making a POST request using the Fetch API to your local server running on http://localhost:80.

Server Response: Your PHP script effectively executes and writes to a file but fails to return the output correctly in your JavaScript code.

Fetch Handling: The implementation of .then() is not correctly chained, leading to an undefined result when you expect to access the echo output.

Solution: Modifying the Fetch Implementation

To resolve the undefined results, you need to ensure that the response from your fetch call is properly returned and logged. Here's how:

Step-by-Step Breakdown of the Fix

Return the Response: When you call response.text(), you must return its value to be correctly captured in the following .then() chain.

Here’s how to do it:

[[See Video to Reveal this Text or Code Snippet]]

Alternative Simplified Syntax: You can also write it more concisely without using the curly braces:

[[See Video to Reveal this Text or Code Snippet]]

Error Handling: Ensure to correct the error handling section by using .catch() instead of chaining another .then(). This will help you catch any errors that occur during the fetch process effectively.

Conclusion

By implementing these changes in your JavaScript code, you should be able to see the correct output when sending HTTP fetch requests from your React application. Now, instead of undefined, you’ll be able to successfully log "Hello World" in your console, indicating that your fetch request is functioning as intended.

Don't let fetch issues hold you back! With this simple fix, you can ensure that you're getting accurate and expected responses from your server.