JSFiddle - React, Tailwind, and code Playground

HTML

<iframe name="site_frame" id="site_frame" src="https://jsfiddle.net">
</iframe>

<p><a href="http://karthickinfotech.blogspot.in/" target="site_frame">First site</a></p>
<p><a href="http://www.sanwebtutorials.blogspot.in/" target="site_frame">Second site</a></p>
<p><a href="http://www.justdial.com/" target="site_frame">Third site</a></p>

<iframe id="code_frame">
    <textarea id="code"></textarea>
</iframe>

JavaScript

document.getElementById('site_frame').onload = function () {    
    console.log("Frame loaded!");
    var siteFrameDoc = getIFrameDocument(document.getElementById('site_frame')),        
        siteFrameHtml = siteFrameDoc.getElementByTagName('html'); 
        wrapper = document.createElement('div');
    wrapper.appendChild(siteFrameHtml.cloneNode(true));
    

    var codeFrameDoc = getIFrameDocument(document.getElementById('code_frame'));
    var textarea = codeFrameDoc.getElementById("code");
    console.log(textarea);
       
    textarea.value = wrapper.innerHtml; 
};

function getIFrameDocument(iframe) {	  
    return iframe.contentDocument || iframe.contentWindow.document;     
}