JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" value="Click me" id="btn"/>

JavaScript

function foo(x) {
    var dom = x.document.documentElement.outerHTML;
    console.log(dom);
}

$('#btn').click(function() {
    var popup = window.open('http://www.google.com', '_blank', 'width=500,height=500');
    setTimeout(function(){foo(popup);}, 3000);
});