JSFiddle - React, Tailwind, and code Playground

HTML

<div class="header">
    <h1>test case</h1>
</div>
<div class="content clearfix">
    <div id="side-bar">menu</div>
    <div id="content-zone">page content <button>add more</button></div>
</div>

CSS

html, body {
    height: 100%;
    margin: 0px; 
    padding: 0px;
}
.header {
    height: 10%;
    background-color: red;
}
.content {
    height: 90%
}
    #side-bar {
        height: 100%;
        width: 30%;
        float: left;
        background-color: blue;
    }
    #content-zone {
        min-height: 100%;
        height: auto;
        width: 70%;
        float: left;
        background-color: yellow;
    }

.clearfix:before, .clearfix:after {
    content: "";
    display: table;
    line-height: 0;
}
.clearfix:after {
    clear: both;
}

JavaScript

$('button').click(function(){
    $('#content-zone').append($('#content-zone').text());
});