JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://rawgit.com/Reactive-Extensions/RxJS/master/dist/rx.all.js"></script>
<div>
<span style="font-size: 20pt">Hello </span>
<span style="font-size: 5pt; display: middle;" id="AAA">World </span>
<span style="font-size: 10pt">etc </span>
<span style="font-size: 10pt">etc</span>
</div>

JavaScript

const element = document.querySelector('#AAA');
const computed = window.getComputedStyle(element);

[...computed].forEach((e) => {  
  	console.log( e, ' : ', computed.getPropertyValue(e) );
});