scrollToTopDom.addEventListener('click', () => { let scrollTopTimer = setInterval(function () { let top = document.body.scrollTop || document.documentElement.scrollTop; let speed = top / 3; if (document.body.scrollTop !== 0) { document.body.scrollTop -= speed; } else { document.documentElement.scrollTop -= speed; } if (top === 0) { clearInterval(scrollTopTimer); } }, 30); });