JSFiddle - React, Tailwind, and code Playground

HTML

<div id="test">

</div>

CSS

#test {
  background-color:red;
  width:100px;
  height:100px;
  box-shadow: 10px 10px 5px 0px rgba(0,0,0,0.75);
  border: 2px solid green;
}

JavaScript

var el = document.getElementById("test");
el.innerHTML = el.innerHTML + el.getBoundingClientRect().width + "<br />";
el.innerHTML = el.innerHTML + el.clientWidth + "<br />";
el.innerHTML = el.innerHTML + el.offsetWidth + "<br />";