How to make smooth scroll effect but with scrolling stop at a specified height?

I know how to make this scroll effect to an element having some class/id. What I don’t get is to make the scroll stop at 20px above this element. I’ve seen examples that do it with document.getElementById() . like this:

function scrollToJustAbove(element, margin=20) {
  let dims = element.getBoundingClientRect();
  window.scrollTo(window.scrollX, dims.top - margin);
}

But, in my case I also need a smooth transition that is what I want (like my link in plnrk). How can I do it?

this is my code:

https://plnkr.co/edit/3NX4FK5QrjiTwYgK5vwj?p=preview

  setTimeout(() => {
    const classElement = document.getElementsByClassName("myclass");
    if(classElement.length > 0){
      classElement[0].scrollIntoView({ block: 'start',  behavior: 'smooth'});
    }
  }, 100);

Answer

Use window.scrollTo() instead of element.scrollIntoView()

The scrollTo method is Polymorphic. Apart from the params you already know, it instead also takes just an object (dictionary) in which you can specify the scroll behavior, like so:

<script>
 function scrollToJustAbove(element, margin=20) {
   let dims = element.getBoundingClientRect();
   window.scrollTo({
    top: dims.top - margin,
    behavior: 'smooth'
   });
 }

 setTimeout(() => {
   const classElement = document.getElementsByClassName("myclass");
   if(classElement.length > 0){
     scrollToJustAbove(classElement[0]);
   }
 }, 100);
</script>

Working Example: https://plnkr.co/edit/UevhAN4NmTCdw65dzuPe?p=preview