JSFiddle - React, Tailwind, and code Playground

HTML

<div class="test">margin-top: </div>

CSS

.test {
    margin: 20px;
}

JavaScript

(function () {
    var elem,
        style;
    elem = document.querySelector('.test');
    style = getComputedStyle(elem);
    elem.innerHTML += style.marginTop;
}());