JSFiddle - React, Tailwind, and code Playground
HTML
<div id="container" class="main-class"></div>
CSS
.main-class {
border: 1px solid gray;
width: 500px;
height: 100px;
padding: 10px;
}
JavaScript
$(document).ready(function() {
var width = $("#container").width();
var height = $("#container").height();
alert(`${width} x ${height}`);
});