<link href="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
<script src="//code.jquery.com/jquery-1.11.1.min.js"></script>
<!------ Include the above in your HEAD tag ---------->
<button class="btn btn-dark icon-revealed">
<span class="glyphicon glyphicon-cloud-download"></span>
<p>Download</p>
</button>
.btn.icon-revealed > span {
left: -30px;
display: block;
width: 0;
-webkit-transition: all .5s ease-in-out;
-moz-transition: all .5s ease-in-out;
-o-transition: all .5s ease-in-out;
-ms-transition: all .5s ease-in-out;
}
.btn.icon-revealed:hover > span {
width: 20%;
-webkit-transform: translate(2em,0);
-moz-transform: translate(2em,0);
-o-transform: translate(2em,0);
-ms-transform: translate(2em,0);
}
.btn.icon-revealed > p {
display: block;
}
