JS Function solution?

Question

JS function solution?

//function outside of constructor function and associate it with objects
function Person(name,age){
this.name=name;
this.age=age;
}
function age(){
return 2021-this.age;
}
var P=new Person(1998);
document.write(P.age());

Answer 1

to give to all Person instances the function:

Person.prototype.age = function() {
return new Date().getFullYear()-this.age;
};

to give to only P instance the function:

P.age = function() {
return new Date().getFullYear()-this.age;
};