function extend(Child, Parent) {
    var F = function() { }
    F.prototype = Parent.prototype;
    Child.prototype = new F();
    Child.prototype.constructor = Child;
    Child.superclass = Parent.prototype;
}

function Box(){
  console.log("constructor");
}

Box.prototype.show = function(){
  console.log("show();");
};

function IconBox(){
  //IconBox.superclass.constructor();
  console.log("constructor IconBox");
};


//extend(IconBox,Box);
//IconBox.prototype = Object.create(Box.prototype);

IconBox.prototype = new Box();

var box = new IconBox();

box.show();