Smooth scroll to the top of the page using JavaScript

When you want to scroll to the top of the page, you can do so instantly or smoothly. Smooth scrolling can provide a more pleasant user experience, especially when the page is long. But _how_ do you do it using JavaScript?
The first step is to determine the total distance to the top of the page. This can be done with the help of Document.documentElement or Document.body and Element.scrollTop. Then, as long as the distance is greater than zero, you can scroll by a fraction of the distance from the top. This fraction can be adjusted to control the speed of the scroll.
Finally, to animate the scrolling, you can use Window.requestAnimationFrame(). This method allows you to perform animations in a more efficient way, ensuring that the browser can optimize the animation and avoid unnecessary repaints.
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const scrollToTop = () => {
  const c = document.documentElement.scrollTop || document.body.scrollTop;
  if (c > 0) {
    window.requestAnimationFrame(scrollToTop);
    window.scrollTo(0, Math.floor(0.05 * c));
  }
};

scrollToTop(); // Smooth-scrolls to the top of the page

Finally, to animate the scrolling, you can use Window.requestAnimationFrame(). This method allows you to perform animations in a more efficient way, ensuring that the browser can optimize the animation and avoid unnecessary repaints.
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> Smooth scrolling raises some accessibility concerns. It is highly recommended to allow users to disable this feature or use a media query to disable it on devices with reduced motion.

From 30-seconds-of-code: scroll-to-top