classy.js

class A { }
class B extends A {
  method() { super.x = 1; return super.x; }
}
var b = new B();
b.method(); // undefined (no property x on A.prototype or above)
b.hasOwnProperty('x'); // true (own property created on receiver by [[set]])

class C extends B {
  get x() { return "gotten" }
}
var c = new C();
c.x; // "gotten" (getter invoked)
c.method(); // undefined (no setter invoked or error thrown)
c.x; // 1 (property now shadows getter on C.prototype)