How to make group opening animation and scroll animation?

Question

Vue.js

Good day! Made positioning on the point of the scrollbar when the group is opened (gets + - to the center of the open group):

onGroupOpen(e) {
  if(e.length > 0) {
    let navbar = document.getElementByClassName('v-navigation-drawer__content') [0];
    let target = document.getElementById(e[0]);
    if(target) {
      navbar.scrollTop = (navbar.offsetHeight * e.length - (target.offsetTop+200));
    } 
  } 
}

But all this happens without animation, how to make the animation of the scroll, and the disclosure of the group?