Debugging Email and Password Errors in NodeJS with MySQL

Learn how to troubleshoot and fix issues when checking email and password on NodeJS with MySQL. Obtain insights into common pitfalls and straightforward solutions!
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Debugging Email and Password Errors in NodeJS with MySQL

When building web applications, one common hurdle developers face is handling user authentication— specifically validating login credentials like email and password. In this post, we'll explore how to effectively troubleshoot a scenario where a user’s email and password check fails even when the credentials exist in the database.

Understanding the Issue

In the example provided, the goal is to check if the user’s entered email and password match an entry in the MySQL database. The error occurs when the console outputs undefined undefined, indicating that the values for email and password aren't being passed correctly from the front end to the back end. This means that the problem likely doesn't stem from the SQL query itself but rather from the data transmission process.

Symptoms of the Problem

Console Output: The server logs show undefined for both email and password.

Incorrect Response: Despite having an existing account, the application responds with "Your Email or Password is wrong".

Steps to Diagnose and Fix the Issue

1. Verify Frontend Data Submission

The first step is to confirm that the form data is being sent correctly from your frontend to your backend. Here’s how you can do that:

Inspect HTML Form: Ensure that the input fields for email and password have their name attributes set correctly. Here’s an example:

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Check Form Submission: Make sure your form is correctly structured to submit data. The button should be properly integrated into a <form> tag:

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2. Debugging in NodeJS

After ensuring that the frontend is adequately set up, let's turn our attention back to the backend:

Check that you’re parsing incoming request body data correctly. If you're using Express, make sure you have the body parser middleware set up:

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Log incoming values before executing your SQL query to verify they are being received:

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3. Review Your SQL Query

While the core issue likely lies within data transmission, having a properly constructed SQL query is critical for functionality:

Ensure your SQL syntax is correct and using parameterized queries to avoid SQL injection. Here’s a safer way to structure your query:

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4. Backend Response Handling

After running your SQL check, respond appropriately based on the results:

Send a meaningful response back to the client, rather than only logging to the console. For example:

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Conclusion

Check your frontend form setup.

Ensure your backend is properly configured to receive data.

Use secure coding practices for your SQL queries.

With these techniques, you can enhance your understanding of user authentication in web applications and build a more robust system.