2.rest_spread.js

// REST OPERATOR

const data = [
  {
    id: 1,
    title: "The Lord of the Rings",
    publicationDate: "1954-07-29",
    author: "J. R. R. Tolkien",
    genres: [
      "fantasy",
      "high-fantasy",
      "adventure",
      "fiction",
      "novels",
      "literature",
    ],
    hasMovieAdaptation: true,
    pages: 1216,
    translations: {
      spanish: "El señor de los anillos",
      chinese: "魔戒",
      french: "Le Seigneur des anneaux",
    },
    reviews: {
      goodreads: {
        rating: 4.52,
        ratingsCount: 630994,
        reviewsCount: 13417,
      },
      librarything: {
        rating: 4.53,
        ratingsCount: 47166,
        reviewsCount: 452,
      },
    },
  },
  {
    id: 2,
    title: "The Cyberiad",
    publicationDate: "1965-01-01",
    author: "Stanislaw Lem",
    genres: [
      "science fiction",
      "humor",
      "speculative fiction",
      "short stories",
      "fantasy",
    ],
    hasMovieAdaptation: false,
    pages: 295,
    translations: {},
    reviews: {
      goodreads: {
        rating: 4.16,
        ratingsCount: 11663,
        reviewsCount: 812,
      },
      librarything: {
        rating: 4.13,
        ratingsCount: 2434,
        reviewsCount: 0,
      },
    },
  },
  {
    id: 3,
    title: "Dune",
    publicationDate: "1965-01-01",
    author: "Frank Herbert",
    genres: ["science fiction", "novel", "adventure"],
    hasMovieAdaptation: true,
    pages: 658,
    translations: {
      spanish: "",
    },
    reviews: {
      goodreads: {
        rating: 4.25,
        ratingsCount: 1142893,
        reviewsCount: 49701,
      },
    },
  },
  {
    id: 4,
    title: "Harry Potter and the Philosopher's Stone",
    publicationDate: "1997-06-26",
    author: "J. K. Rowling",
    genres: ["fantasy", "adventure"],
    hasMovieAdaptation: true,
    pages: 223,
    translations: {
      spanish: "Harry Potter y la piedra filosofal",
      korean: "해리 포터와 마법사의 돌",
      bengali: "হ্যারি পটার এন্ড দ্য ফিলোসফার্স স্টোন",
      portuguese: "Harry Potter e a Pedra Filosofal",
    },
    reviews: {
      goodreads: {
        rating: 4.47,
        ratingsCount: 8910059,
        reviewsCount: 140625,
      },
      librarything: {
        rating: 4.29,
        ratingsCount: 120941,
        reviewsCount: 1960,
      },
    },
  },
  {
    id: 5,
    title: "A Game of Thrones",
    publicationDate: "1996-08-01",
    author: "George R. R. Martin",
    genres: ["fantasy", "high-fantasy", "novel", "fantasy fiction"],
    hasMovieAdaptation: true,
    pages: 835,
    translations: {
      korean: "왕좌의 게임",
      polish: "Gra o tron",
      portuguese: "A Guerra dos Tronos",
      spanish: "Juego de tronos",
    },
    reviews: {
      goodreads: {
        rating: 4.44,
        ratingsCount: 2295233,
        reviewsCount: 59058,
      },
      librarything: {
        rating: 4.36,
        ratingsCount: 38358,
        reviewsCount: 1095,
      },
    },
  },
];


function getBooks(id){
    return data.find((d) => d.id ==id);
}

const bookThree = getBooks(3)

const { pages, genres} = bookThree;

//const primaryGenre = genres[0]
//const secondaryGenre = genres[1]

const [primaryGenre, secondaryGenre, ...otherGenres] = genres;

primaryGenre;
secondaryGenre;
otherGenres;

// after destructuring an array and access the first and second item, the rest of the items are stored in a variable we assign using (...)
// it is placed at the end of the destructing operation 


//SPREAD OPERATOR///
//this is also used on arrays and objects

const newGenres = [...genres, 'epic fantasy']; //at the end
const newGenresStart = [ 'epic fantasy', ...genres] //at the start
newGenres;
newGenresStart
//the spread operator adds a new item to an array or object. 
//the operator is instanciated by using (...)

const updatedBook = {...bookThree, moviePublicationDate: '2025-08-02', pages: 2025};
updatedBook;
//in objects you can either add a new property or overide an existing one