// Constructor

function Book(title, author, year) {

this.title = title;

this.author = author;

this.year = year;

}

Book.prototype.getSummary = function() {

return `${this.title} was written by ${this.author} in ${this.year}.`;

};

Book.prototype.getAge = function() {

const years = new Date().getFullYear() - this.year;

return `${this.title} is ${years} years old.`;

};

// Revise / Change Year

Book.prototype.revise = function(newYear) {

this.year = newYear;

this.revised = true;

};

// Instantiate an Object

const book1 = new Book('Book One', 'John Doe', 2013);

const book2 = new Book('Book Two', 'Jane Doe', 2016);

console.log(book1.getSummary());

console.log(book2.getSummary());

console.log(book2);

book2.revise(2018);

console.log(book2);

console.log(book2.getAge());