[Maxmaxmaximus7]

пофиксил, ускорил скорость работы) добавил поддержку статических, приватных и даже публичных свойств =)

function Class( description ) {

    return Class.extend( description );

}



Class.prototype['constructor'] = function() {};



Class['extend'] = function( description ) {

    description = parse( description );
    description.prototype = this.prototype;

    var prototype = new description( description.prototype, constructor );
    var _constructor = prototype['constructor'];


    function constructor() {
        return _constructor.apply( this, arguments );
    }

    constructor.prototype = prototype;
    constructor['extend'] = this['extend'];

    return constructor;
};



function parse( description ) {

    var code = description.toString().match( /\{([\s\S]*)\}$/ )[1];

    code = parentSupport( code );
    code = privateSupport( code );
    code = publicSupport( code );

    return new Function( 'parent,static', code );
}



function parentSupport( code ) {

    var regExp = /\bparent\b\s*\.\s*(\w+)\s*\((.*?)\)/img;

    code = code.replace( regExp, function( match, method, params ) {
        var separator = /\S/.test( params ) ? ',' : '';
        return 'parent.' + method + '.call(this' + separator + params + ')';
    } );

    return code;
}



function privateSupport( code ) {

    var fix = '___';
    var regExp = /\bprivate\b.([\w_]+)/img;

    code = code.replace( regExp, function( match, prop ) {
        return 'this.' + fix + prop + fix;
    } );

    return code;
}



function publicSupport( code ) {

    var regExp = /\bpublic\b.([\w_]+)/img;

    code = code.replace( regExp, function( match, prop ) {
        return 'this.' + prop;
    } );

    return code;
}

//########################################################  static

var Cat = new Class( function() {

    this.constructor = function() {
        static.cnt++
    }

    static.cnt = 0

} )

new Cat();
new Cat();
new Cat();

alert( Cat.cnt ) // 3

//########################################################  private

var Cat = new Class( function() {

    public.name = 'Cat'
    private.age = 11;

} );

var q = new Cat();

alert( q.name ); // Cat
alert( q.age ); // undefined