function Person(name, surname, yearOfBirth){
this.name = name,
this.surname = surname,
this.yearOfBirth = yearOfBirth };

Object.defineProperty(Person, 'fullName', {
    get: function(){
        return this.name +' '+ this.surname
    }
});

var test = new Person("test", "test", 9999);
console.log(test.fullName);

Object.defineProperty(Person.prototype, 'fullName', {
    get: function() {
        return this.name +' '+ this.surname
    }
});

this.name = name;
this.surname = surname;
this.yearOfBirth = yearOfBirth;

Object.defineProperty(Person.prototype, 'fullName', {
    get() {
        return `${this.name} ${this.surname}`;
    }
});