JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<div id="parent" style="display:none;">
    <div id="target" style="height:100px;display:block;">
        a
    </div>
</div>

JavaScript

$(document).ready(function(){
    alert($("#target").height());
});