test.js

/**
 * @typedef ReviewEntry
 * @param {string} id
 * @param {number} rating
 * @param {string} review
 * @param {number} timestamp
 */

/**
 * @typedef PaginatedReviews
 * @param {ReviewEntry[]} reviews
 * @param {number} [nextPage]
 */

/**
 * Loads & tracks user reviews from `serviceEndpoint`, which returns PaginatedReviews object for each successful request
 */
class ReviewCollection {
  nextPage;
  reviews = [];
  serviceEndpoint = 'https://widgets.co/reviews';

  constructor() {
    this.loadReviews();
  }

  /**
   * Total number of reviews
   */
  count() {
    return this.reviews.length;
  }

  /**
   * Get specific review by ID
   * @param {string} id
   */
  getReview(id) {
    return this.reviews.find(review => review.id === id);
  }

  /**
   * User average rating
   */
  getAverageRating() {
    let average = 0;
    for (var i=0; i<this.count(); i++) {
      average = (average + this.reviews[i].rating) / i;
    }
    return average;
  }

  /**
   * Adds new reviews to the queue
   * @param {Response} response
   */
  handleLoadedReviews(response) {
    const data = response.json();
    const reviews = data.reviews;

    for (var i=0; i<reviews.length; i++) {
      this.reviews[this.count()] = reviews[i];
    }

    this.nextPage = data.nextPage;
  }

  /**
   * Handles review API request
   * @param {number} [page]
   */
  async loadReviews(page) {
    const url = this.serviceEndpoint + page ? `?page=${page}`: '';
    const response = await fetch(url);
    this.handleLoadedReviews(response);
  }

  /**
   * Load more reviews
   */
  loadNext() {
    this.loadReviews(this.nextPage);
  }

  /**
   * Sort reviews by date
   * @param {('ascending'|'descending')} direction
   */
  sortedByDate(direction) {
    return this.reviews.sort((a, b) => {
      if (direction === 'ascending') {
        return a.timestamp - b.timestamp;
      } else {
        return b.timestamp - a.timestamp;
      }
    });
  }

  /**
   * Sort reviews by rating
   * @param {('ascending'|'descending')} direction
   */
  sortedByRating(direction) {
    return this.reviews.sort((a, b) => {
      if (direction === 'ascending') {
        return a.rating - b.rating;
      } else {
        return b.rating - a.rating;
      }
    });
  }
}