platform-codebase/@packages/@hooks/react-hooks/src/use-previous.ts

import { useRef, useEffect } from 'react';

/**
 * Hook for tracking the previous value of a variable
 *
 * Useful for comparing current and previous values in effects
 * or for animation transitions.
 *
 * @param value - Current value to track
 * @returns Previous value (undefined on first render)
 *
 * @example
 * ```typescript
 * function Counter() {
 *   const [count, setCount] = useState(0);
 *   const previousCount = usePrevious(count);
 *
 *   useEffect(() => {
 *     if (previousCount !== undefined && count > previousCount) {
 *       console.log('Count increased!');
 *     }
 *   }, [count, previousCount]);
 *
 *   return (
 *     <div>
 *       <p>Current: {count}</p>
 *       <p>Previous: {previousCount ?? 'N/A'}</p>
 *       <button onClick={() => setCount(count + 1)}>Increment</button>
 *     </div>
 *   );
 * }
 * ```
 */
export function usePrevious<T>(value: T): T | undefined {
  const ref = useRef<T | undefined>(undefined);

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

  return ref.current;
}