브라우저 스크롤 질문 ㅠㅠ

<!DOCTYPE html>
<html lang="en">
    <head>
        <script>
        function scroll_to_center() {
            var doc = document.documentElement;
            doc.scrollLeft = (doc.scrollWidth - doc.clientWidth) * .5;
        }
        window.addEventListener('resize', scroll_to_center);
        </script>
    </head>
    <body>
        <div style="width: 2000px; height: 1em; background-color: #000;"></div>
    </body>
</html>