Private functions and Variables ExtJs4?

Question

In my current project I am using ExtJs3.3.
I have created many classes which had private variables and functions. For eg:

MyPanel = function(config){
  config = config || {};

  var bar = 'bar';//private variable

  function getBar(){//public function
     return bar;
  }

  function foo(){
     //private function
  }

Ext.apply(config, {
  title: 'Panel',
  layout: 'border',
  id: 'myPanel',
  closable: 'true',
  items: []
});

  MyPanel.superclass.constructor.call(this, config);
};
Ext.extend(MyPanel , Ext.Panel, {
  bar: getBar
});
Ext.reg('MyPanel', MyPanel);

I understand that the new way of doing things in ExtJs4 is to use the Ext.define method. So as my above piece of code would look something like this:

Ext.define('MyPanel', {
  extend: 'Ext.panel.Panel',

  title: 'Panel',
  layout: 'border',
  closable: true,

  constructor: function(config) {

     this.callParent(arguments);
  },

});

So what I want to know is how can I define private variables and functions in ExtJs4 similar to the way I done it in ExtJs3?
In other words I understand that the Ext.define method will take care of defining, extending and registering my new class, but where should I declare javascript var's which are not properties of the class itself but are needed by the class.

MyPanel = function(config){
  //In my Ext3.3 examples I was able to declare any javascript functions and vars here.
  //In what way should I accomplish this in ExtJs4.

  var store = new Ext.data.Store();

  function foo(){
  }
  MyPanel.superclass.constructor.call(this, config);
};

Answer 1

I am not a big fan of enforcing private variables like this but of course it can be done. Just setup a accessor function (closure) to the variable in your constructor/initComponent function:

constructor: function(config) {
    var bar = 4;
    this.callParent(arguments);

    this.getBar = function() {
        return bar;
    }
},...

Answer 2

Thats exactly what config is for, check this from Extjs docs:

config: Object List of configuration options with their default values, for which automatically accessor methods are generated. For example:

Ext.define('SmartPhone', {
     config: {
         hasTouchScreen: false,
         operatingSystem: 'Other',
         price: 500
     },
     constructor: function(cfg) {
         this.initConfig(cfg);
     }
});

var iPhone = new SmartPhone({
     hasTouchScreen: true,
     operatingSystem: 'iOS'
});

iPhone.getPrice(); // 500;
iPhone.getOperatingSystem(); // 'iOS'
iPhone.getHasTouchScreen(); // true;
iPhone.hasTouchScreen(); // true

That way you hide your actual field and still have access to it.