JSFiddle - React, Tailwind, and code Playground

HTML

<div id="message"></div>
<iframe id="iframe" src="//example.com"></iframe>

CSS

iframe {
    width: 500px;
    height: 300px;
}

JavaScript

focus();
var listener = addEventListener('blur', function() {
	if(document.activeElement === document.getElementById('iframe')) {
		message.innerHTML = 'Clicked';
	}
    removeEventListener(listener);
});