JSFiddle - React, Tailwind, and code Playground

HTML

<div id="bla" class="myClass myClass1">bla</div>

CSS

.myClass {
    margin-left:10%;
    padding-right:20%;
}

JavaScript

var m = window.getMatchedCSSRules($('#bla').get(0))[0].style["margin-left"]
alert(m)