JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
		<div class="subContainer">
			<div class="navParent">
				<div class="nav">
					hi
				</div>
			</div>
			<div class="changeableContent">
				<a id="contentAdd">Click me to add content</a>
			</div>
		</div>
	</div>

CSS

html {
	height: 100%;
}

body {
	height: 100%;
}

.container {
	height: 100%;
}

.subContainer  {
	height: 100%;
}

.navParent {
	height: 100%;
}

.nav {
	height: 100%;
}

.changeableContent {
	height: 100%;
}

.subContainer {
	display: flex;
	flex-direction: row;
}

.nav {
	width: 304px;
	background: black;
}

.changeableContent {
	background-color: yellow;
	display: flex;
	flex: 1;
	flex-direction: column;
}

JavaScript

jQuery(document).ready(function($) {
    $('#contentAdd').on('click', function(event) {
        event.preventDefault();
        for (var i = 0; i < 100; i++)
            $('.changeableContent').append($('<p></p>').text('SOME TEXT'));
    });
});