JSFiddle - React, Tailwind, and code Playground

HTML

<iframe src="http://fiddle.jshell.net/kBh7c/2/show/" frameBorder="0" allowTransparency="true" scrolling="no"></iframe>

CSS

html, body {
    background: #d0e5ff;
}

JavaScript

if (window.addEventListener) window.addEventListener("message", handleIframelyMessage, false);
else window.attachEvent("onmessage", function (e) { return handleIframelyMessage.call(this,e||window.event); });

function handleIframelyMessage (event) {
    var m;
    if (typeof event.data !== "string" || !(m = /^iframely:size:(.*)/.exec(event.data))) {
        return;
    }
    
    var params = m[1].split("&");
    var size = {};
    for (var i = 0; i < params.length; ++ i) {
        var param = params[i].split("=");
        var key = decodeURIComponent(param[0]);
        size[key] = decodeURIComponent(param.slice(1).join("="));
    }
    if ('width' in size)  size.width  = parseInt(size.width,10);
    if ('height' in size) size.height = parseInt(size.height,10);
    
    var elems = document.getElementsByTagName("iframe");
    for (var i = 0; i < elems.length; ++ i) {
        var elem = elems[i];
        if (elem.contentWindow === event.source) {
            if ('width' in size)  elem.style.width  = size.width+'px';
            if ('height' in size) elem.style.height = size.height+'px';
            break;
        }
    }
}