JSFiddle - React, Tailwind, and code Playground

HTML

<div id="a"></div>

CSS

#a{
    width: 100px;
    height: 100px;
    border: 1px solid black;
    border-radius: 10px;
}

JavaScript

var a = document.getElementById("a");
console.log(window.getComputedStyle(a).getPropertyValue("border-radius"))