JSFiddle - React, Tailwind, and code Playground

HTML

<div id="d"></div>

CSS

body {
    height: 3000px
}
#d {
    background: tan;
    width: 300px;
    height: 300px;
    position:fixed;
    left:200px;
    top: 200px;
}

JavaScript

var d = document.getElementById('d');

d.addEventListener("mousemove", function(e) {
    //var offset = offset_obj(this);
    this.innerHTML = "Top: "+(e.pageY-$(this).offset().top) + " " + "Left: "+(e.pageX-$(this).offset().left);
});

// -----

function offset_obj(obj) {
  var ol = ot = 0;
  if (obj.offsetParent) {
    do {
      ol += obj.offsetLeft;
      ot += obj.offsetTop;
    } while (obj = obj.offsetParent);
  }
  return {
    left: ol,
    top: ot
  };
}