Without calling function, javascript adding property to object

Question

var jhon = {
                 name : 'Jhon' ,
                 lastName : 'Smith' ,
                 calculateAge : function (){
                                    this.age = 2016 - this.yearOfBirth ;
                                }
            };

1. console.log(jhon) => "age" propery not in the o/p

2. jhon.calculateAge(); console.log(jhon);

   ==> "age" property present in the o/p

3. (This is what confuse me)

   console.log(jhon); jhon.calculateAge(); console.log(jhon);

   ===> "age" property present in both the o/p

Can anyone please explain the reason ?