var person = {
    firstName:"John",
    lastName: "Doe",
    fullName: function () {
        return this.firstName + " " + this.lastName;
    }
}
person.fullName();         // Will return "John Doe" 

 var person = {
    fullName: function() {
        return this.firstName + " " + this.lastName;
    }
}
var person1 = {
    firstName:"John",
    lastName: "Doe",
}
var person2 = {
    firstName:"Mary",
    lastName: "Doe",
}
person.fullName.call(person1);  // Will return "John Doe" 

 var person = {
    fullName: function() {
        return this.firstName + " " + this.lastName;
    }
}
var person1 = {
    firstName:"John",
    lastName: "Doe",
}
var person2 = {
    firstName:"Mary",
    lastName: "Doe",
}
person.fullName.call(person2);  // Will return "Mary Doe" 

var person = {
    fullName: function(city, country) {
        return this.firstName + " " + this.lastName + "," + city + "," + country;
    }
}
var person1 = {
    firstName:"John",
    lastName: "Doe",
}
person.fullName.call(person1, "Oslo", "Norway");