Скачать или смотреть Understanding the Basics of useState Hook in ReactJS

Dive into the ReactJS `useState` hook with our comprehensive guide. Learn how to manage state in functional components effectively and fix common pitfalls.
---
This video is based on the question https://stackoverflow.com/q/64024762/ asked by the user 'Subrato Pattanaik' ( https://stackoverflow.com/u/13847690/ ) and on the answer https://stackoverflow.com/a/64024846/ provided by the user '95faf8e76605e973' ( https://stackoverflow.com/u/8680805/ ) 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: Basics implementation example of useState Hooks in ReactJS

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.
---
Understanding the Basics of useState Hook in ReactJS: A Step-by-Step Guide

In the world of ReactJS, managing state in functional components is crucial for building interactive applications. One of the primary tools for achieving this is the useState hook. In this post, we will explore a common problem developers face when using the useState hook and how to solve it effectively.

The Problem at Hand

Recently, a ReactJS developer encountered an issue with adding elements to an array stored in state using the useState hook. The original goal was to update an array and display its contents whenever a button was clicked. However, the developer noticed that while the first click successfully added a new element, subsequent clicks only replaced the last element instead of adding new ones.

Expected Behavior

On the first click: The array should include the new element.

On subsequent clicks: The array should continue to grow with each new element, rather than overriding the previous one.

The Source of Confusion

This issue arose because the initial array was defined within the component's function. As a result, it reinitialized to its original values ([1,2,3]) every time the component rendered. This is where many developers can get tripped up when starting with React hooks.

The Solution

To resolve this issue, the array should be defined outside of the component, allowing you to maintain the changes made to the state. Let's dive into the step-by-step solution and see how this can be implemented:

Step 1: Define the Array Outside the Component

By moving the initial array definition outside the Example component, you ensure it doesn't get reset on every render.

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

Step 2: Utilize useState Properly

Next, you need to set your initial state using useState, which will hold the new array that gets updated:

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

Step 3: Update the Array on Button Click

Within the button click handler, we will update both newArray (to add new elements) and newElement (to keep track of the new number to be added).

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

Step 4: Render the Updated Array

Finally, you can render the array using the map function:

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

Full Updated Code Example

Here’s how the complete code looks with the suggested changes:

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

Conclusion

By following these steps, you can effectively utilize the useState hook in ReactJS to manage and update state without encountering common pitfalls. Remember, always make sure the initial state is defined in a way that persists through re-renders to avoid unexpected behaviors. This will help you create smoother and more predictable applications using React.

Feel free to share this guide with anyone who may benefit from a clear understanding of the useState hook!