Basic automatic scroller with requestAnimationFrame

ezScroller.js

// @todo https://miketaylr.com/posts/2014/11/document-body-scrolltop.html
let animReference = null;

function _start(loop)
{
  animReference = requestAnimationFrame(loop);
}

function _stop()
{
  if (animReference)
  {
    cancelAnimationFrame(animReference);
    animReference = null;
  }
}

export default function EZScroller(scrollableElement, targetElement, duration=600) {
  let _from = scrollableElement.scrollTop;
  let _to = targetElement.offsetTop;
  let _started_at = Date.now();

  function loop()
  {
    let _step = Math.min(1, (Date.now() - _started_at) / duration);
    scrollableElement.scrollTop = (_from + _step * (_to - _from));
    if (_step === 1)
    {
      return _stop();
    }

    _start(loop);
  }

  _stop();
  _start(loop);
}