Array of Objects

Everyday tasks of a developer include manipulating an array of objects of the same type. This means that all objects in the array have absolutely the same set of properties, but with different values.

const books = [
  {
    title: "The Last Kingdom",
    author: "Bernard Cornwell",
    rating: 8.38,
  },
  {
    title: "Beside Still Waters",
    author: "Robert Sheckley",
    rating: 8.51,
  },
  {
    title: "The Dream of a Ridiculous Man",
    author: "Fyodor Dostoevsky",
    rating: 7.75,
  },
];

To iterate over such an array, use the standard for...of loop. To get property values of each object, use dot notation, since the set of properties and their names are the same in each object, only their values differ.

for (const book of books) {
  // Book object
  console.log(book);
  // Title
  console.log(book.title);
  // Author
  console.log(book.author);
  // Rating
  console.log(book.rating);
}

For example, generate a list of all book titles in the books collection.

const bookNames = [];

for (const book of books) {
  bookNames.push(book.title);
}

console.log(bookNames); // ["The Last Kingdom", "Beside Still Waters", "The Dream of a Ridiculous Man"]

Calculate the average rating of the entire collection. To do this, add up all the ratings and then divide this value by the number of books in the collection.

let totalRating = 0;

for (const book of books) {
  totalRating += book.rating;
}

const averageRating = (totalRating / books.length).toFixed(1);
console.log(averageRating); // 8.2