JSFiddle - React, Tailwind, and code Playground

HTML

<div class="button" data-number="5"><a href="javascript:;">button</a></div>

CSS

.button{
 background-color:red;
 color:#fff;
 width:70px;
}
.button:before{
 min-width:0px;
 content: attr(data-number);
}

.button:hover .button:before{
 color:#000;
}