JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div class="left">
        <ul>
            <li>een</li>
            <li>twee</li>
            <li>drie</li>
        </ul>
    </div>
    <div class="right">
        <p>Bla bla bla bla bla bla bla bla</p>
        <p>Bla bla bla bla bla bla bla bla</p>
        <p>Bla bla bla bla bla bla bla bla</p>
    </div>
</div>

CSS

body {
    margin: 0;
    padding: 0;
}

.container { 
    width: 100%;    
}

.left { 
    float: left; 
    width: 20%;
    background: #ffcccc;
}

.right {
    float: right;
    width: 80%;
    background: #ccccff;
}

JavaScript

$(document).ready(function() {
	$('.right').css({ 
        minHeight: $('.left').height() 
    });
	$('.left').css({ 
        minHeight: $('.right').height() 
    });
});