How do you create custom hooks? Custom hooks कैसे बनाते हैं?

// Custom hook - reusable logic
function useWindowWidth() {
  const [width, setWidth] = useState(window.innerWidth);
  
  useEffect(() => {
    function handleResize() {
      setWidth(window.innerWidth);
    }
    window.addEventListener('resize', handleResize);
    return () => window.removeEventListener('resize', handleResize);
  }, []);
  
  return width;
}

// Using custom hook
function Component() {
  const width = useWindowWidth();
  return <p>Width: {width}</p>;
}

// Custom hook for API calls
function useApi(url) {
  const [data, setData] = useState(null);
  const [loading, setLoading] = useState(true);
  
  useEffect(() => {
    fetch(url)
      .then(res => res.json())
      .then(data => {
        setData(data);
        setLoading(false);
      });
  }, [url]);
  
  return { data, loading };
}