JAVASCRIPT
Custom usePrevious Hook to Track Previous State
Create a `usePrevious` custom React hook to easily access the previous value of a prop or state variable within your functional components.
import { useRef, useEffect } from 'react';
function usePrevious(value) {
const ref = useRef();
useEffect(() => {
ref.current = value;
}, [value]);
return ref.current;
}
// Example Usage:
// function Counter() {
// const [count, setCount] = useState(0);
// const prevCount = usePrevious(count);
// return (
// <div>
// <p>Current: {count}</p>
// <p>Previous: {prevCount}</p>
// <button onClick={() => setCount(count + 1)}>Increment</button>
// </div>
// );
// }
How it works: The `usePrevious` hook provides a way to get the value of a state or prop from the previous render cycle. It leverages `useRef` to store the value between renders without causing re-renders itself. Inside a `useEffect` hook, the `ref.current` is updated with the current `value` after the render, ensuring that on the next render, `ref.current` holds the value from the *previous* render.