JSFiddle - React, Tailwind, and code Playground

HTML

<div id="slideout">
    <div id="slidecontent">
        Yar, there be dragonns herre!
    </div>
    <div id="clickme">
    </div>
</div>

CSS

body {
    overflow-x: hidden;
}
#slideout {
    background: #666;
    position: absolute;
    width: 280px;
    height: 80px;
    top: 45%;
    right:-280px;
    padding-left: 20px
}
    
#clickme {
    position: absolute;
    top: 0; left: 0;
    height: 20px;
    width: 20px;
    background: #ff0000;
}

#slidecontent {
    float:left;
}

JavaScript

$(function () {
    var rightVal = -280;
    $("#clickme").click(function () {
        rightVal = (rightVal * -1) - 280;
        $(this).parent().animate({right: rightVal + 'px'}, {queue: false, duration: 500});
    });
});