JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://dev.sencha.com/deploy/ext-4.0.0/resources/css/ext-all.css">

JavaScript

Ext.create('Ext.form.Panel', {
    title: 'Form',
    renderTo: Ext.getBody(),
    dockedItems: [
        {
            xtype: 'toolbar',
            dock: 'top',
            items: {
                text: 'Click to Load Store',
                handler: function(btn) {
                    var combo = btn.up('form').down('combobox');
                    combo.getStore().loadData([ 
                        [ 'dothis' ], 
                        [ 'dothat' ], 
                        [ 'dosomething' ] 
                    ]);
                }
            }                     
        }
    ],
    items: {
        xtype: 'combobox',
        emptyText: 'Functions',
        store: [ 'none' ]
    }
});