JSFiddle - React, Tailwind, and code Playground

HTML

<form>
    <div>
        <iframe name="foo" src="about:blank"></iframe>
    </div>
</form>

JavaScript

$(document).ready(function() {
    window.alert("isWindow(window): " + isWindow(window));
    window.alert("isWindow(window.frames['foo']): " + isWindow(window.frames['foo']));
    window.alert("isWindow(div): " + isWindow($("div").get(0)));
});

function isWindow(obj) {
    return obj === obj.window;
}