about defining method object

Question

why my method object doesn't output?

function person3(name, age) {
this.name= name;
this.age = age;
this.yearOfBirth = bornYear;
}
function bornYear() {
return 2016 - this.age;
}
var p8=new person3("Alex",29);
document.write(p8.yearOfBirth);

output is:
function bornYear() { return (2016 - this.age); }

Answer 1

Instead of
p8.yearOfBirth
write
p8.yearOfBirth()
It should work, but I wouldn't define object methods this way

Answer 2

Value of yearOfBirth is function, so you should use yearOfBirth as 'yearOfBirth()'.