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);