Pagination algorithm (only show some of the page from total page)

pagination.ts

const pagingRange = (currentPage: number, { min = 1, totalPage = 20, length = 3 } = {}): Array<number> => {
  if (length > totalPage) length = totalPage;

  let start: number = currentPage - Math.floor(length / 2);
  if (currentPage === totalPage) {
    start = currentPage - Math.ceil(length / 2);
  }

  start = Math.max(start, min);
  start = Math.min(start, min + totalPage - length);
 
  return Array.from({length: length}, (el, i) => start + i);
}

console.log(pagingRange(20)) // [ 18, 19, 20 ]
console.log(pagingRange(4, { totalPage: 30, length: 3 })) // [ 3, 4, 5]
console.log(pagingRange(12, { totalPage: 12, length: 4})) // [ 9, 10, 11, 12 ]