JSFiddle - React, Tailwind, and code Playground

HTML

<iframe src="http://www.youtube.com/embed/9u_hp7zPir0?wmode=opaque" frameborder="0" id="if1382133712216" allowfullscreen="true" style="width: 620px; height: 290px;"></iframe>
<button id="btn">Click me</button>

CSS

button{position:absolute;top:100px;left:50px;z-index:1;height:50px;width:200px}

JavaScript

document.getElementById('btn').onclick = function() {
    alert('clicked');
}