JSFiddle - React, Tailwind, and code Playground

HTML

<iframe src="http://jsfiddle.net"></iframe>

JavaScript

$(window)
    .focus(function() {
        console.log("focus");
    })
    .blur(function() {
        console.log("blur");
        if (document.activeElement.tagName.toLowerCase() == "iframe") {
            console.log("still focus");
        }
    });