JSFiddle - React, Tailwind, and code Playground

HTML

<div class="box">
  box
</div>

<b class="box2"></b>

<div class="result">
    
</div>

CSS

.box {
  border: 3px solid black;     
}

.box2 {     
  border: 3px solid black;  
}

JavaScript

var result = "box :" + $(".box").css("border");
result += "<br/><br/>box2:" + $(".box2").css("border");
result += "<br/><br/>DOM :" + window.getComputedStyle($(".box2")[0], null).getPropertyValue("border-left-width");

$(".result").html(result);