How to use the usePrevious hook for tracking previous state in Next.js



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In Next.js or any React application, you can use the usePrevious custom hook to track the previous state of a variable. The idea is to use the useEffect hook to store the current state in a ref, and then you can access the previous state whenever the component re-renders.

Here's an example implementation of the usePrevious hook:

jsx
import { useRef, useEffect } from 'react';

function usePrevious(value) {
  const ref = useRef();

  useEffect(() => {
    ref.current = value;
  }, [value]);

  return ref.current;
}

Now you can use this usePrevious hook in your Next.js component:

jsx
import { useState, useEffect } from 'react';
import usePrevious from '../path-to-usePrevious-hook'; // Update the path based on your project structure

function YourComponent() {
  const [count, setCount] = useState(0);

  // Use the usePrevious hook to get the previous value of count
  const prevCount = usePrevious(count);

  useEffect(() => {
    console.log(`Current count: ${count}`);
    console.log(`Previous count: ${prevCount}`);
  }, [count, prevCount]);

  return (
    <div>
      <p>Current Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment Count</button>
    </div>
  );
}

export default YourComponent;

In this example, the useEffect hook will log both the current count and the previous count whenever the count state changes. The usePrevious hook is used to get the previous value of count. Note that the usePrevious hook is reusable and can be used for tracking the previous state of any variable in your components.

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