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Learn how to maintain existing state values while updating specific ones in React functional components without losing data!
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How to Preserve State Values in React Functional Components

React is a powerful library that enables you to build dynamic user interfaces. However, when working with functional components, it can get tricky to maintain certain state values while updating others. If you've ever found your state data getting overridden, you're not alone! In this guide, we will walk through the issue of losing other state values when updating a single one, and how you can effectively resolve this using modern React features.

The Problem

Imagine you have a functional component to edit a product with various properties such as name, ean, type, weight, color, and active. You want to update one property, say name, but you're accidentally overwriting all the other properties with empty data. Here is the core of the problem:

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This code is causing you to lose the previously stored states like ean, type, etc. When you call setProduct, you’re replacing the entire object instead of updating just one property.

The Solution

To maintain your existing values while updating a specific one, you can use the spread operator (...) in a function to spread the current state values into a new object, and then overwrite the intended property.

Step-by-Step Implementation

Here’s how to fix the issue systematically:

Use the Spread Operator: Instead of creating a new object with only the name, spread the existing product state into the new object, and then update the name property.

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Apply the Same Logic to Other Handlers: This pattern should be applied to all the other handlers for updating ean, type, and so forth. Here’s an example for the ean property:

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Complete Implementation: Below is how the component can look now, with handlers for each property structured correctly:

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Why This Works

By using the spread operator, you're creating a new object that contains all of the current properties from product, and then selectively updating just the property you want. This technique effectively prevents state loss and keeps your component functioning as expected.

Conclusion

Using the spread operator is a fundamental pattern to ensure that you preserve other state values while updating one in React functional components. This technique allows for flexible and maintainable code, enabling you to build more complex forms and components without the burden of losing critical data. Implementing this pattern will make your React applications more robust and user-friendly.

Now, you can confidently manipulate state in React without fear of losing other values. Happy coding!