JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://dev.sencha.com/deploy/ext-4.0.7-gpl/resources/css/ext-all.css">
<script src="http://dev.sencha.com/deploy/ext-4.0.7-gpl/ext-all-debug.js"></script>

JavaScript

Ext.onReady(function(){
    var panel = Ext.create('Ext.Panel', {
        renderTo: Ext.getBody(),
        html: 'content, content, content, content, content, content, content, content, content, content, content, content, content, content, content, content, content, content, content, content, content, content'
    });
    
    /*panel.getEl().mask();
    if (panel.getEl().isMasked()) {
        alert('masked');
    }*/
    
    var myMask = new Ext.LoadMask(panel, {msg:"Please wait..."});
    myMask.show();
    
    Ext.ComponentMgr.each(function(i, value){
        if ((value instanceof Ext.LoadMask) && value.isVisible() && 
            (value.ownerCt === panel || value.floatParent == panel))
        {
            alert('masked');
            return false;
        }
    });
});