javascript inheritance with prototypes

function A() {
  this.aParam = 'a sababa',
  this.aFunction = function() { return this.aParam; }
};
function B() {
  this.bParam = 'b sababa',
  this.bFunction = function() { return this.bParam; }
};
function C() {
  this.cParam = 'c sababa',
  this.cFunction = function() { return this.cParam; }
};
function D() {
  this.dParam = 'd sababa',
  this.dFunction = function() { return this.dParam; }
};
B.prototype = new A();
C.prototype = new B();
D.prototype = new C();

var a = new A();
var b = new B();
var c = new C();
var d = new D();

// ----------------------
console.log(d.dParam)      // d sababa
console.log(d.cParam)      // c sababa
console.log(d.aFunction()) // a sababa