Implementing the useTrackedEffect Custom Hook

Here's the implementation of a useTrackedEffect hook for React:

The useTrackedEffect hook is a powerful enhancement to React's standard useEffect. Here's how it works:

Core Functionality

The hook tracks which specific dependencies changed between renders, giving you precise information about what triggered your effect. This is incredibly useful for debugging and performance optimization.

Key Components

1. Dependency Tracking:

• Uses useRef to store the previous render's dependencies
• Compares current dependencies with previous ones on each render

2. Change Detection Algorithm:

The reduce function creates an object that maps:

• The index of each changed dependency
• Both the previous (from) and current (to) values

3. Conditional Execution:

• Only executes the effect if at least one dependency changed
• Passes the change information to your effect callback

4. Cleanup Handling:

• Supports cleanup functions just like standard useEffect
• Checks if the effect has a cleanup property that's a function

Usage Example

Benefits

• Precise debugging: Immediately see which dependency caused a re-render
• Performance optimization: Target your optimizations at the exact dependencies causing unnecessary re-renders
• Better control flow: Make decisions in your effect based on which specific values changed

This hook is especially valuable in complex components with multiple dependencies where standard useEffect doesn't provide enough context about what triggered the effect.