JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en">
<style>

 #A {
    display:inline-block;
    background:red;	
	  padding-right:100px;
 }

</style>

<body> 

 <div id="A">a</div> 		   	  
 <div id="RESULT"></div> 	   
	  
 <script>  
   document.getElementById("RESULT").innerHTML = "the width of A is:" + window.getComputedStyle(document.getElementById("A")).width;
 </script>

</body>

</html>