function User() {
this.firstname = '';
this.surname = '';
this.setFirstName = function(name) {
this.firstname = name
}
this.setSurname = function(name) {
this.surname = name
}
this.getFullName = function() {
return this.firstname + ' ' + this.surname;
}
}
var user = new User();
user.setFirstName("Петя");
user.setSurname("Иванов");
alert(user.firstname) // Петя
var user2 = new User();
user2.setFirstName('Фёдор');
user2.setSurname("Марков");
alert(user2.firstname) // Федор