scripts/my/namespace/Animal.js

/* 
 * Define a namespace.
 */
$ns("my.namespace");

/**
 * Define a class which extends MXComponent.
 * A MXComponent is a very popular super class.
 * Actually, in this case, we can also use MXObject instead.
 * MXObject is the super class of MXComponent.
 */
my.namespace.Animal = function()
{
	/**
	 * In MXFramework, it always use 'me' instead of 'this'.
	 */
	var me = $extend(MXComponent);
	/**
	 * 'base' is almost the same as 'super' in Java.
	 */
	var base = {};


	/**
	 * Define a public field.
	 * Every public member should under 'me'.
	 */
	me.name = null;

	/**
	 * Define a private field.
	 * The names of a private members always start with an underline.
	 */
	 var _something = null;
	 var _someVariable = 0;


	/**
	 * Override a public method.
	 * 'init' method will be automatically called immediately after the instance is created.
	 * Even though, you can also set the 'autoInit' field to false if you need lazy intialization.
	 */
	base.init = me.init;
	me.init = function(p_options)
	{
		base.init(p_options);
	};


	/**
	 * Define a public function.
	 */
	me.sayHi = function()
	{
		if (_canSayHi())
		{
			/* 
			  String.format provides ability to substitute string with JSON object or array.
			  In MXFramework you can use the following format methods.
			  - String.format    String.format("Hi, {name}!", { name: "Henry" }); String.format("Hi, {0}", [ "Henry" ])
			  - Date.format      Date.format(new Date(), "yyyy-MM-dd HH:mm:ss"); Date.format(new Date(), "yy年M月d日");
			  - Number.format    Number.format(12.53212, "0.00"); Number.format(123, "00000000");
			 */
			return String.format("Hi, I'm a {name}", { name: me.name });
		}
	};


	/**
	 * Define a private function.
	 */
	function _canSayHi()
	{
		// MXFramework has a series of methods for type assertions.
		return isString(me.name);
	}


	/**
	 * This is the end of class.
	 */
	return me.endOfClass(arguments);
};

scripts/your/namespace/Cat.js

$ns("your.namespace");

// Import the super class.
$import("my.namespace.Animal");

/**
 * Cat inherits from Animal.
 */
your.namespace.Cat = function()
{
	var me = $extend(my.namespace.Animal);
	/*
	 * Change the initial value of name.
	 */
	me.name = "Cat";
	var base = {};

	me.nickName = "kitty";

	base.init = me.init;
	me.init = function(p_options)
	{
		base.init(p_options);
		if (isEmptyString(me.nickName) && isString(me.name))
		{
			me.nickName = me.name;
		}
	};

	/**
	 * Override 'sayHi' method.
	 */
	base.sayHi = me.sayHi;
	me.sayHi = function()
	{
		// $format is a shortcut to String.format, Date.format and Number.format.
		return base.sayHi() + $format(" You can call me {0}", [ me.nickName ]);
	};

	return me.endOfClass(arguments);
};

// Import Cat class. The Animal class will be automatically imported with Cat.
$import("your.namespace.Cat");

// Create a new instance with default values.
var cat = new your.namespace.Cat();
alert(cat.sayHi());

// Create a new instance with initial values using JSON.
// In MXFramework, class only accepts JSON object as constructure parameter.
var tomCat = new your.namespace.Cat({
    nickName: "Tom"
});
alert(tomCat.sayHi());