Скачать или смотреть Resolving the Issue of useEffect Not Triggering in React

A detailed guide to troubleshoot and fix the issue of `useEffect` not being triggered when updating state in React applications.
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This video is based on the question https://stackoverflow.com/q/72331507/ asked by the user 'Saroj Shrestha' ( https://stackoverflow.com/u/4217452/ ) and on the answer https://stackoverflow.com/a/72331545/ provided by the user 'Soufiane Boutahlil' ( https://stackoverflow.com/u/11498568/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the Problem: React useEffect Not Triggering

As a React developer, one might face the perplexing issue of the useEffect hook not being triggered as expected. This can happen even when the state seems to be updated properly. A common scenario involves updating an array state, which leads to confusion when useEffect fails to respond to changes.

Let’s take a look at a sample case to understand this better. A developer has the following state initialization and a function meant to update the state:

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

The updateFilterValue function updates this state but the useEffect that should react to changes in uncheckedColArr is not being triggered as expected. This leads to a frustrating situation, leaving many developers wondering what went wrong.

The Solution: Correctly Updating State in React

The root of the problem lies in how the state is updated. React's useState hook relies on immutability to detect changes. If you update the state using a reference to the same array instead of creating a new copy, React will not recognize the change, and consequently, useEffect won't be triggered.

Step-by-Step Fix

Creating a New Array:
Use the spread operator to create a new copy of the array when updating state. This ensures that React is aware of the updated state.

Incorrect Approach:

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

Correct Approach:

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

Implementation:
Here’s how the corrected updateFilterValue function would look:

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

Verifying the Solution:
After making this change, you should see that your useEffect hook triggers correctly when uncheckedColArr is updated. Use the following code to check if your useEffect is functioning as intended:

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

Summary

When you encounter the issue of useEffect not triggering, remember that state updates in React are based on changes in state immutability. Always create a new reference for state arrays to ensure React recognizes the changes.

By applying the simple fix outlined above, you can ensure your useEffect hooks function as anticipated, leading to smoother and more predictable interactions in your React applications.