JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://dev.sencha.com/deploy/ext-3.4.0/resources/css/ext-all.css">
<script src="http://dev.sencha.com/deploy/ext-3.4.0/adapter/ext/ext-base-debug.js"></script>
<script src="http://dev.sencha.com/deploy/ext-3.4.0/ext-all-debug.js"></script>

JavaScript

Ext.onReady(function() {
    var filePanel = new Ext.Panel({
         html: '<iframe src="/" style="width:100%; border:none;"></iframe>'
    });

    var fileUploadWindow = new Ext.Window({
        modal: true,
        autoHeight: true,
        title: 'File Upload',
        //layout: 'fit',
        closable: true,
        draggable: true,
        autoDestroy: false,
        width: 570,
        items: [filePanel],
        shadow: true,
        buttons: [{
            xtype: 'button',
            text: 'Close',
            handler: function (button) {
                fileUploadWindow.hide();
                fileStore.reload();
            }
        }]
    });
    
    filePanel.on('afterrender', function(){
        var frame = filePanel.getEl().child('iframe');
        frame.on('load', function(){ 
            var innerDoc = (frame.dom.contentDocument) ?
                frame.dom.contentDocument : 
                frame.dom.contentWindow.document;
            var height = innerDoc.body.scrollHeight;
            
            frame.setHeight(height);
            filePanel.setHeight(height);
            fileUploadWindow.center();
        });
        
    }, filePanel);
    fileUploadWindow.show();
});