Options of Pagination Algorithms with JavaScript

pagination.js

/* First Example */ 
function pagination(
  totalItems,
  selectedPage,
  itemsLimit = 4,
){
  // Calculating the total of pages by dividing the limit and the numbers of items 
  const totalPages = Math.ceil(totalItems / itemsLimit); 
  const startPage = 1;
  const endPage = totalPages;
  
  // Veryfing if the current page isn't out of range 
  if (selectedPage < 0) { 
      selectedPage = 1;
  } else if (selectedPage > totalPages) { 
     selectedPage = totalPages;
  }
  
  let delta = 2,
      left = selectedPage - delta,
      right = selectedPage + delta,
      lastPage = null,
      pages = [];
  
  for (let currentPage = 1; currentPage <= totalPages; currentPage++){
      // Adding the first, last and intermediary pages
      if (currentPage === 1 || currentPage === totalPages || (currentPage >= left && currentPage <= right)) { 
          if (lastPage && (currentPage - lastPage) >= 2) {
            pages.push('...')
          }
      
          pages.push(currentPage)
          
          lastPage = currentPage
      }
  }
  
  return pages;
}

/* Second Example - Without dots */
function paginationWithoutPages(
  totalItems,
  selectedPage,
  itemsLimit = 4
) {
  // Calculating the total of pages by dividing the limit and the numbers of items 
  const totalPages = Math.ceil(totalItems / itemsLimit)
  const delta = 2; 
  const left = selectedPage - delta; 
  const right = selectedPage + delta;
  let pages = [];
  
  pages = Array.from({length: totalPages}, (value, key) => key + 1)
          .filter(page => page && page >= left && page <= right)
  
  return pages;
}