JSFiddle - React, Tailwind, and code Playground

HTML

<span 
onmouseover="enter(this)" onmouseout="leave(this)">BUTTON</span>

CSS

span {background:silver; font:normal 15px verdana;
position:relative; top:10px; padding:5px 10px; border:2px solid grey; cursor:pointer}

JavaScript

function enter(elem){
     elem.style.backgroundColor = 'lightgreen';
 }
 function leave(elem){
     elem.style.backgroundColor = 'silver';
 }