Working with Immutable arrays

• in react, many operations need to be immutable
  • so these techniques are absolutely essential for react development
• we’re learning how to add/delete/update elements without touching the original array
  • always make new array
  • these would normally be abstracted into some functions

// books is just an object that contains book objects
//1. Adding book
const newBook = {
  id: 6,
  title: "harry potter",
  author: "jk",
};
const booksAfterAdd = [...books, newBook];
 
// 2.Deleting book
const booksAfterDelete = booksAfterAdd.filter((book) => books.includes(book));
 
// 3. updating book object in the array
const booksAfterUpdate = booksAfterDelete.map((book) =>
  book.id == 5 ? { ...book, pages: book.pages + 100 } : book
);