JSFiddle - React, Tailwind, and code Playground

HTML

<DIV id="rect" style="position:relative;top:0px;left:0px;width:100px;height:200px;border:1px solid #000000;">Some content</DIV>
<DIV id="posout"></DIV>

JavaScript

var div = document.getElementById('rect');
var posout = document.getElementById('posout');
posout.innerHTML = 'top:' + div.style.top + '</br>left:' + div.style.left;   
div.onclick = function () {
    div.style.webkitTransform = 'rotate(90deg)';
    div.style.mozTransform = 'rotate(90deg)';
    div.style.msTransform = 'rotate(90deg)';
    div.style.oTransform = 'rotate(90deg)';
    div.style.transform = 'rotate(90deg)';
    x = parseInt(div.style.top) + Math.cos(90) * parseInt(div.style.height);
    y = parseInt(div.style.left) + Math.sin(90) * parseInt(div.style.height);
    posout.innerHTML = 'top:' + y + '</br>left:' + x;
}