How to Prevent Data Duplication in Node.js with fs.writeFile

Learn how to efficiently handle form submissions in Node.js and avoid data duplication in your JSON file using fs.writeFile.
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Solving Data Duplication Issues When Using fs.writeFile in Node.js

When developing applications that involve user input, one common challenge is managing data correctly. A frequent problem developers encounter is data duplication, especially when working with file systems. In this guide, we will explore how to prevent duplicate data when writing to a JSON file using Node.js and the fs module.

The Problem: Data Duplication on Refresh

Suppose you have a simple web form that captures user responses and stores them in a JSON file. You've created a Node.js application using Express, which allows users to submit their answers. However, after the form is submitted and the JSON file is saved, if a user refreshes the page, the last input is resubmitted, leading to data duplication in the JSON file.

This can be frustrating because it causes your application to behave incorrectly and produce unwanted data. So how can we address this issue effectively?

The Solution: Using Redirects to Prevent Resubmission

Understanding the Problem of Resubmission

When a user submits a form, the browser typically uses the POST method to send the data to the server. If a user refreshes the page right after submission, the browser may attempt to resubmit the same POST request. Many browsers will prompt users about the resubmission, but this is not always handled cleanly, leading to duplicate entries in your JSON file.

The Key Change: Redirecting After Submission

The simplest way to tackle this issue is to change the response behavior after the form has been processed. Instead of sending the user back to the form using res.sendFile(), you can use a redirect with res.redirect().

Here's how to implement this:

Locate the following line in your app.post() handler:

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

Replace it with:

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

Final Code Snippet

Here’s how your updated app.post() handler will look after the change:

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

Benefits of Using Redirects

Prevent Data Duplication: Users cannot accidentally resubmit their data after refreshing the page.

Improved User Experience: The user gets redirected to a clean state of the form without reloading the same entry.

Maintain HTTP Protocol: You follow the post/redirect/get (PRG) pattern, which is a standard approach in web development for handling form submissions.

Conclusion

By implementing a simple redirect after handling form submissions in your Node.js application, you can effectively prevent data duplication when users refresh the page. This approach not only improves the accuracy of the data being stored but also enhances the overall user experience. Now you can handle user input more confidently without worrying about duplicate entries in your JSON files. Happy coding!