[js, support react] check a element whether on screen/shown (can used to check "scrolled to bottom?" )

 function isInViewport(element) {

        const rect = element.getBoundingClientRect();

        return (

            rect.top >= 0 &&

            rect.left >= 0 &&

            rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) &&

            rect.right <= (window.innerWidth || document.documentElement.clientWidth)

        );

    }