JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://extjs.cachefly.net/ext-4.1.0-gpl/resources/css/ext-all.css">

JavaScript

Ext.create('Ext.form.Panel', {
    title: 'Simple Form',
    bodyPadding: 5,
    width: 350,
    // The form will submit an AJAX request to this URL when submitted
    url: 'save-form.php',

    // Fields will be arranged vertically, stretched to full width
    layout: 'anchor',
    defaults: {
        anchor: '100%'
    },
    // The fields
    defaultType: 'textfield',
    items: [{
        fieldLabel: 'First Name',
        name: 'firstName',
        allowBlank: false
    },{
        fieldLabel: 'Last Name',
        name: 'lastName',
        allowBlank: false
    }],
    // Reset and Submit buttons
    buttons: [{
        text: 'Reset',
        handler: function() {
            this.up('form').getForm().reset();
        }
    }, {
        text: 'Submit',
        formBind: false, //only enabled once the form is valid
        disabled: false,
        handler: function() {         
            var panel = this.up('form');
            var form = panel.getForm();
            if (form.isValid()) {
                form.submit({
                    success: function(form, action) {
                       Ext.Msg.alert('Success', action.result.msg);
                    },
                    failure: function(form, action) {
                        Ext.Msg.alert('Failed', action.result.msg);
                    }
                });
            } else {
                fieldNames = [];                
                fields = panel.getInvalidFields();
                for(var i=0; i <  fields.length; i++){
                    field = fields[i];
                    fieldNames.push(field.getName());
                 }
                console.debug(fieldNames);
                Ext.MessageBox.alert('Invalid Fields', 'The following fields are invalid: ' + fieldNames.join(', '));
            }
        }
    }],
    getInvalidFields: function() {
        var invalidFields = [];
        Ext.suspendLayouts();
        this.form.getFields().filterBy(function(field) {
            if...