JSFiddle - React, Tailwind, and code Playground

HTML

<textarea  id="inpt" cols="30" rows="10"></textarea>
<div><input type="submit" value="append" id="btn" style="width:60px;height:20px;background:grey"></div><br>
<iframe id="fr" name="fr" style="width:300px;height:300px;"></iframe>
<script type="text/javascript">
document.getElementById('inpt').innerHTML = "document.write('awesome')";
if (typeof addEventListener !== "undefined") {
    addEvent = function (obj, evt, fn) {
        obj.addEventListener(evt, fn, false);
    };

    removeEvent = function (obj, evt, fn) {
        obj.removeEventListener(evt, fn, false);
    };
} else if (typeof attachEvent !== "undefined") {
    addEvent = function (obj, evt, fn) {
        var fnHash = "e_" + evt + fn;

        obj[fnHash] = function () {
            var type = event.type,
                relatedTarget = null;

            if (type === "mouseover" || type === "mouseout") {
                relatedTarget = (type === "mouseover") ? event.fromElement : event.toElement;
            }

            fn.call(obj, {
                target: event.srcElement,
                type: type,
                relatedTarget: relatedTarget,
                _event: event,
                preventDefault: function () {
                    this._event.returnValue = false;
                },
                stopPropagation: function () {
                    this._event.cancelBubble = true;
                }
            });
        };

        obj.attachEvent("on" + evt, obj[fnHash]);
    };
}
var _script = document.createElement('script');
_script.type = 'text/javascript';
var iFrame = document.getElementById('fr'),
    iFrameBody,
    t = document.getElementById("inpt"),
    btn = document.getElementById('btn');

function injectJS(content, val) {
    removeJS();
    var windowVal;
    if (iFrame.contentDocument) {
        windowVal = iFrame.contentDocument;
        iFrameBody = iFrame.contentDocument.getElementsByTagName('body')[0];
    } else if (iFrame.contentWindow) {
        windowVal =...