$defined = function (v) {
return v != undefined;
}

Class = function () {
var base = {};
for (var k=0; k<arguments.length; k++) {
//{{new arguments[k]() with custom constructor field.
var o = arguments[k].prototype;
o.constructor = arguments[k];
arguments[k].call(o);
//}}
for (key in o) base[key] = o[key];
}
function Klass () {
// for every class one object cache.
var clso = null;
function klass() {
if (arguments.length<=0 && clso!=null) {
// hit cache.
return clso;
}
if ($defined(this.constructor.init)) {
// use init() for class initialization.
this.constructor.init.apply(this, arguments);
}
clso = this;
}
klass.prototype = base;
return klass;
}
return Klass();
}

A = new Class();
A.init = function () {
this.x = 400;
this.y = 300;
}
B = new Class(A);
B.init = function () {
this.y = 200;
this.z = 100;
}
C = new Class(B);
C.init = function () {
this.z = 0;
}
c = new C();
alert(c.x);
alert(c.y);
alert(c.z);