JSFiddle - React, Tailwind, and code Playground

HTML

<div id="mydiv" style="width: 100%;">ttttttttrtrooooo ooooooottttttt</div>

<div id="showHeight"></div>
<div id="showWidth"></div>

JavaScript

$(document).ready(function() {
    
    var myDiv = $('#mydiv');

$('#showWidth').html(myDiv.css('width'));
$('#showHeight').html(myDiv.css('height'));
    
});