JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://dropthebit.com/demos/stickyfloat/stickyfloat.js"></script>
<div class="header"> HEADER </div>
<div class="container"> 
<div class="addthis">
        <!-- AddThis Button BEGIN -->
<div class="addthis_toolbox addthis_floating_style addthis_32x32_style">
<a class="addthis_button_facebook"></a>
<a class="addthis_button_twitter"></a>
<a class="addthis_button_google_plusone_share"></a>
<a class="addthis_button_pinterest_share"></a>
<a class="addthis_button_compact"></a>
<a class="addthis_button_email"></a>
</div>
<script type="text/javascript" src="//s7.addthis.com/js/300/addthis_widget.js#pubid=undefined"></script>
<!-- AddThis Button END -->
</div>
    <p>ICONS SHOULD STAY <br> WITHIN THIS GRAY BOX</p>
</div>
<div class="footer"> SHOULD NOT GO BELOW THIS LINE</div>

CSS

.header{
	width:400px;
	background: #F00;
	height:100px;
	margin:0 auto;
}
.container{
	position:relative;
	height:400px;
	width:400px;
	margin:0 auto;
	background: #999;
}
.footer{
	height:700px;
	width:400px;
	background: #F0F;
	margin:0 auto;
}
.addthis{
	position:absolute;
	top:0;
	left:-50px;
}
/* vsync solution  */
.addthis_floating_style {
    position: static;
}

p{text-align:center;}

JavaScript

$(function() {
    $('.addthis').stickyfloat({duration:0});
    console.log($('.addthis')); // Handler for .ready() called.
});