JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://extjs.cachefly.net/ext-4.1.1-gpl/resources/css/ext-all.css">
<script src="http://extjs.cachefly.net/ext-4.1.1-gpl/ext-all-debug.js"></script>

JavaScript

Ext.onReady(function() {
    Ext.create('Ext.window.Window', {
        width: 500,
        height: 300,
        
        layout: {
            type: 'vbox',
            align: 'stretch'
        },
        
        items: [{
                xtype: 'panel',
                title: 'panel1',
                flex: 1
            },{
                xtype: 'panel',
                title: 'form1',
                flex: 1,
                
                collapsible: true,
                titleCollapse: true,
                collapseDirection: Ext.Component.DIRECTION_BOTTOM,
                animCollapse: false,
                
                listeners: {
                    afterrender: function(panel) {
                        if (panel) {
                            panel.collapse(Ext.Component.DIRECTION_BOTTOM);
                        }
                    }
                }
        }]
    }).show();
});