function Parent() {

             this.a = 1;

             this.b = [1, 2, this.a];

             this.c = { demo: 5 };

             this.show = function () {

                 console.log(this.a , this.b , this.c.demo );

             }

         }

         function Child() {

             this.a = 2;

             this.change = function () {

                 this.b.push(this.a);

                 this.a = this.b.length;

                 this.c.demo = this.a++;

             }

         }

         Child.prototype = new Parent();

         var parent = new Parent();

         var child1 = new Child();

         var child2 = new Child();

         child1.a = 11;

         child2.a = 12;

         parent.show();

         child1.show();

         child2.show();

         child1.change();

         child2.change();

         parent.show();

         child1.show();

         child2.show();