JSFiddle - React, Tailwind, and code Playground

HTML

<div id="test"></div>

CSS

* {
  box-sizing: border-box;
}

div {
  height: 100px;
  width: 100px;
  padding: 10px;
  background-color: red;
}

JavaScript

console.log(window.getComputedStyle(document.getElementById('test')).getPropertyValue('width'))