Solving the undefined Issue in React + Express.js URL Parameters

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Introduction

Problem Overview

Let’s look at the code snippets provided to understand the situation better.

Example Code Snippet

Here’s the snippet of the onClick function:

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

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As you can see, when the button is clicked, the console logs the user as undefined, but directly accessing the URL with a proper query string works fine.

Solution: Fixing the URL and Fetch Call

Now, let’s address the issue step-by-step.

Step 1: Correct the Protocol in the URL

The primary issue here lies in the URL you're using in your front-end function. You have mistakenly included https:// and http:// together, which is incorrect. You only need to specify http://.

Updated Code Snippet

Here’s the corrected version of your getBackend function:

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

Step 2: Ensure Proper Fetch Implementation

In the fetch method, specify the URL using the corrected variable directly. This way, the request knows where to look for the backend resource. Ensure you're using url as shown above instead of a hard-coded string.

Conclusion

Now, you can confidently handle user information in your web application without running into undefined errors when using URL parameters. Happy coding!