JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://dev.sencha.com/deploy/ext-4.1.0-gpl/resources/css/ext-all.css">
<script src="http://dev.sencha.com/deploy/ext-4.1.0-gpl/ext-all-debug.js"></script>

JavaScript

Ext.onReady(function() {
    Ext.create('Ext.window.Window', {
        width: 300,
        height: 300,

        layout: {
            type: 'vbox',
            align: 'stretch'
        },

        items: [{
            xtype: 'panel',
            title: 'panel1',
            flex: 1},
        {
            xtype: 'panel',
            title: 'panel3',
            flex: 1,

            collapsible: false,
            collapsed: true,
            animCollapse: false,
            collapseDirection: 'bottom',
            titleCollapse: true}]
    }).show();
});