loadMoreArticles2

loadMoreArticles = direction => {
  const { allArticles, currentCategory } = this.state;
  const currentCategoryId = this.categories.find(
    category => category.name === currentCategory
  ).id;
  const currentCategoryArticles = allArticles.filter(
    article => article.UserId === currentCategoryId
  );

  const pagedArticles = page => {
    const lastIndex = page * this.articlesPerPage;
    const firstIndex = lastIndex - this.articlesPerPage;
    return currentCategoryArticles.slice(firstIndex, lastIndex);
  };

  const getLastPage = () =>
    Math.floor(currentCategoryArticles.length / this.articlesPerPage);

  // eslint-disable-next-line default-case
  switch (direction) {
    case 'prev':
      this.setState(prevState => {
        if (prevState.currentPage === 1) {
          return {
            currentPage: getLastPage(),
            currentArticles: pagedArticles(getLastPage())
          };
        } else {
          return {
            currentPage: prevState.currentPage - 1,
            currentArticles: pagedArticles(prevState.currentPage - 1)
          };
        }
      });
      break;

    case 'next':
      this.setState(prevState => {
        if (prevState.currentPage === getLastPage()) {
          return {
            currentPage: 1,
            currentArticles: pagedArticles(1)
          };
        } else {
          return {
            currentPage: prevState.currentPage + 1,
            currentArticles: pagedArticles(prevState.currentPage + 1)
          };
        }
      });
      break;
  }
};