JSFiddle - React, Tailwind, and code Playground

HTML

Click me

JavaScript

document.onclick=function() {
    var popup = open("about:blank", 'bob'),
        frame = $("<iframe/>").appendTo("body")[0];

    setTimeout(function() {
        var docs = {
            popup: popup.document,
            frame: (frame.contentWindow ? frame.contentWindow :
                    frame.contentDocument.document ? frame.contentDocument.document :
                    frame.contentDocument).document
        },
            results = $.map( docs, function( doc, label ) {
                doc.open();
                doc.write("<p>Hello World</p>");
                doc.close();
                try {
                    return label + ": " + $( "p", doc ).css("z-index");
                } catch(x) {
                    return label + ": ERROR " + x.message;
                }
            });
        
        popup.close();
        $( frame ).remove();
        
        alert( results.join("\n") );
    }, 100);
}