JSFiddle - React, Tailwind, and code Playground

HTML

<br /><br /><br />
<div id="container">
    <div id="up">Text<br />Text<br />Text<br /></div>
    <div id="down">Text<br />Text<br />Text<br /></div>
</div>

CSS

#container { width: 300px; height: 300px; border:1px solid red; display:table;}
#up { background: green; display:table-row; height:0;}
#down { background:pink;display:table-row;}

JavaScript

alert(
    '#container height: ' + $('#container').innerHeight() + "\n" +
    '#up height: ' + $('#up').innerHeight() + "\n" +
    '#down height: ' + $('#down').innerHeight()
);