var person1 = {
  firstname: 'Jane',
  lastname: 'Doe',
  getFullName: function() {

    var fullname = this.firstname + ' ' + this.lastname;
    return fullname;

  }
}

// function borrowing
var person2 = {
  firstname: 'John',
  lastname: 'Doe'
}

person1.getFullName.apply(person2); // => John Doe
// Here we are invoking person1's getFullName method but calling it on person2
// Thus we are borrowing person1's function