JSFiddle - React, Tailwind, and code Playground

HTML

<div id="ev-entry" class="ex_event_frame">Testing if the height element is positioned at the center of the screen regardless of the resolution used</div>

CSS

.ex_event_frame {
    left: 39px;
    margin-left: auto;
    margin-right: auto;
    width: 300px;
    height: 300px;
    overflow: auto;
    background: #2e3030;
    color: #ffffff;
    position: absolute;
    z-index: 101;
    -moz-border-radius: 5px;
    -webkit-border-radius: 5px;
    border-radius: 14px;
    -moz-box-shadow: 0 0 10px rgba(0, 0, 0, .4);
    -webkit-box-shadow: 0 0 10px rgba(0, 0, 0, .4);
    -box-shadow: 0 0 10px rgba(0, 0, 0, .4);
    border: 8px solid #105f6b;
}

JavaScript

$(function () {
    $(window).resize(function(){
    var offset = 0,
        viewportHeight = $(window).height(),
        $myDialog = $('#ev-entry');
    console.log(viewportHeight + " "+$myDialog.height() )
    $myDialog.css('top', (offset + (viewportHeight / 2)) - ($myDialog.height() / 2));
    }).resize();
});