How to Effectively Filter Fetched Arrays in React Rendering

Learn how to filter fetched array data in React by managing state properly to render your buttons by category.
---
This video is based on the question https://stackoverflow.com/q/72291742/ asked by the user 'cam_gis' ( https://stackoverflow.com/u/17678225/ ) and on the answer https://stackoverflow.com/a/72292034/ provided by the user 'Igor Loskutov' ( https://stackoverflow.com/u/2123547/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Filtering fetched array in render React

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Effectively Filter Fetched Arrays in React Rendering

As a beginner in React, encountering issues with rendering dynamic data can be frustrating. One common problem is filtering fetched data so it displays correctly based on specific properties. In this guide, we will explore how to effectively filter an array of data fetched from a server, particularly when you want to render categories as buttons based on a specific property.

Understanding the Problem

You have successfully fetched data from a server and stored it in your component's state. However, the rendering process isn't displaying the data correctly. Instead of generating multiple buttons based on each category, you only see one button representing the first data element. This issue is likely due to how React handles state updates and render cycles, especially in an asynchronous environment.

Breaking Down the Solution

To address the problem, let's analyze your existing code and the steps necessary to ensure your fetched data is rendered correctly.

Step 1: Understand State Management

React uses a virtual DOM and a reconciliation process to determine what should be rendered. When you update the state using methods such as setState(), React performs shallow comparisons. If you are merely mutating the state object without creating a new reference, React may fail to recognize that an update has occurred.

Step 2: Update State Properly

To solve the issue of state not updating properly when you push data into the solo array, replace your current state update line:

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

Suggested Change

Change the above line to:

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

By using the spread operator, you're creating a new array reference whenever the state updates. This way, React recognizes the state as changed:

Step 3: A Complete Example

Here’s how your componentDidMount function would look after applying the suggested changes:

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

Step 4: Rendering the Buttons

In your render method, ensure you are properly filtering the solo array based on the categ value:

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

Conclusion

By ensuring that your state updates in React are handled properly—specifically by maintaining immutable state—you can effectively filter and render your fetched data. Avoid mutating the original state and instead create new references to enable React's rendering mechanism. This will help you generate the correct number of buttons for each category based on the dynamic data fetched from your server.

Feel free to reach out for more explanations or help with specific parts of your React project. Happy coding!