JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/extjs/4.2.1/resources/css/ext-all-neptune.css">

JavaScript

Ext.onReady(function () {
    Ext.create('Ext.container.Viewport', {
        width: 300,
        height: 200,
        modal: true,
        style: {
            background: '#dfe8f6'
        },
        layout: 'border',
        items: [{
            region: 'west',
            title: 'Instead of toolbar',
            collapsible: true,
            width: 250,
            tbar: [{
                xtype: 'button',
                text: 'Button',
                style: {
                    background: 'green'
                },
                handler: function () {}
            }]
        }],
        renderTo: Ext.getBody()
    });
});