JSFiddle - React, Tailwind, and code Playground

HTML

<pretty-scroll>
  <ul class='commentlist'>
    <li>Item 1</li>
    <li>Item 2</li>
    <li>Item 3</li>
  </ul>
</pretty-scroll>

JavaScript

function getEventTarget(e) {
      e = e || window.event;
      return e.target || e.srcElement;
    }

    var ul = document.getElementsByClassName('commentlist')[0];
    ul.onclick = function(event) {
      var target = getEventTarget(event);
      var elemPos =  getOffset(target);
      alert(target.innerHTML+" ::: " +elemPos.top + " : " + elemPos.left);
    };
    
 function getOffset( el ) {
    var _x = 0;
    var _y = 0;
    while( el && !isNaN( el.offsetLeft ) && !isNaN( el.offsetTop ) ) {
        _x += el.offsetLeft - el.scrollLeft;
        _y += el.offsetTop - el.scrollTop;
        el = el.offsetParent;
    }
    return { top: _y, left: _x };
}