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.override(Ext.layout.Layout, {
    renderItem: function(item, target, position) {
        
    if (item && item.isFieldLabelable && !item.rendered && item.fieldLabel && item.allowBlank == false) {
        item.fieldLabel += ' <span class="req" style="color:red">*</span>';
}
        
this.callOverridden(arguments);
}
});


//-----------
// test form
//-----------

Ext.create('Ext.form.FieldSet', {
    renderTo: Ext.getBody(),
    height: 100,
    width: 300,
    defaults: {
        xtype: 'textfield'
    },
    items: [{
        fieldLabel: 'Required',
        allowBlank: 0
    },{
        fieldLabel: 'Not Required',
        allowBlank: 1
    }]
});

Ext.create('Ext.form.Panel', {
    renderTo: Ext.getBody(),
    height: 100,
    width: 300,
    defaults: {
        xtype: 'textfield'
    },
    items: [{
        fieldLabel: 'Required',
        allowBlank: 0
    },{
        fieldLabel: 'Not Required',
        allowBlank: 1
    }]
});