JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//extjs.cachefly.net/ext-4.1.0-gpl/resources/css/ext-all-gray-debug.css" />
<script src="//extjs.cachefly.net/ext-4.1.0-gpl/ext-all-dev.js"></script>

JavaScript

Ext.define('MyPanel', {
    extend: 'Ext.panel.Panel',

    title: 'My Panel',

    initComponent: function() {

        var self = this;

        Ext.applyIf(self, {
            items: [
                {
                xtype: 'button',
                text: 'MyButton',
                handler: function() {
                    console.log(this); //the button
                    console.log(self); //the form
                }}
            ]
        });

        self.callParent(arguments);
    }
});

Ext.onReady(function() {

    var p = new MyPanel({
        renderTo: Ext.getBody()
    });


});