How to Save Transformed Data in a useState Constant in React JS

Learn how to effectively manage and transform data using `useState` in React JS by making shallow and deep copies.
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How to Save Transformed Data in a useState Constant in React JS

As a newcomer to React, you might encounter several challenges related to managing state and transforming data. One common issue is saving transformed data into a useState constant after executing operations like slicing or filtering another useState variable. In this guide, we will discuss how to handle this scenario effectively, providing a detailed explanation of the underlying concepts along with practical solutions.

Understanding the Problem

When you fetch data from an API, you often store the raw data in a state variable using useState. But what if you need to modify this data and store the transformed version in another state variable? This can be tricky if you're not familiar with concepts like shallow copy and deep copy.

The Solution: Shallow vs Deep Copy

The core challenge here revolves around the concept of copying objects in JavaScript. There are two types of copies you can make:

Shallow Copy: It copies the properties of an object or array, but if any of those properties are objects themselves, they are still references to the same memory address (meaning changes to them will affect the copied object).

Deep Copy: It creates a wholly independent copy of an object or array. Changes made to the copy do not affect the original object/array.

To ensure that your original data remains unchanged when you modify the transformed data, you need to create a deep copy.

Implementing the Deep Copy

Here's how you can create a deep copy of your transformed data before storing it in state:

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Breakdown of the Code:

Fetching Data: The data is fetched from the API using fetch. You then convert the response to JSON.

Creating a Copy: A shallow copy of the fetched data (reponsefulldata) is created with the spread operator.

Transforming Data: The info property of each tourist object is modified using the .map() method.

Deep Copy: The transformed data is deep-copied using JSON.parse(JSON.stringify(...)). This ensures that Trimmedtoursdata does not affect Fulltoursdata.

Conclusion

Managing multiple pieces of state in React can sometimes be complex, especially when it comes to transforming data. By understanding how shallow and deep copies work, you can confidently manipulate your data without worrying about unintentional side effects.

Next time you need to save transformed data in a useState constant, remember to use a deep copy to keep your original state intact. Happy coding!