JSFiddle - React, Tailwind, and code Playground

HTML

<div class="pane centered"></div>

CSS

.pane {
    width: 200px;
    height: 100px;
    background: blue;
}

.centered {
    position: fixed;
    top: 50%;
    left: 50%;
}

JavaScript

jQuery(document).ready(function($) {
    $(".centered").each(function() {
        $(this).css({
            "margin-left": "-" + ($(this).width() / 2)+"px",
            "margin-top": "-" + ($(this).height() / 2)+"px"
        });
    });
});