function useWindowSize() {
    const [size, setSize] = useState({
        width: window.innerWidth,
        height: window.innerHeight
    });

    useEffect(() => {
        const handleResize = () => {
            setSize({
                width: window.innerWidth,
                height: window.innerHeight
            });
        };

        window.addEventListener('resize', handleResize);
        return () => window.removeEventListener('resize', handleResize);
    }, []);

    return size;
}

// Utilisation
function ResponsiveComponent() {
    const { width, height } = useWindowSize();

    return (
        <div>
            Fenêtre : {width} x {height}
            {width < 768 && <p>Mode mobile</p>}
        </div>
    );
}