JSFiddle - React, Tailwind, and code Playground

HTML

<iframe id="myIframe"></iframe>

JavaScript

var doc = document.getElementById('myIframe').contentWindow.document;
var $html = $('*', doc);

$html.html('\
<!DOCTYPE html>\
<html lang="en">\
<head>\
<style>\
    function test() {\
        return true;\
    }\
</style>\
</head>\
<body>\
<h1>Test</h1>\
</body>\
</html>');

$('#myIframe').contents().find('body').find('h1').text('modified!');

console.log($('#myIframe').contents().find('*').html());