pagination.js

const calculatePages = (length: number, current: number, total: number) => {
  if (length === 0) return []
  if (length === 1) return [current]
  if (total <= length + 4) return Array.from({ length: total }, (_v, i) => i + 1)
  const jumpSize = Math.ceil(length / 2)
  const centerStart = Math.min(Math.max(current - (length - jumpSize), 3), total - length - 1)
  const jumpStart = current <= length + 1 ? 2 : `-${jumpSize}`
  const jumpEnd = current >= total - length ? total - 1 : `+${jumpSize}`
  return [1, jumpStart, ...Array.from({ length }, (_v, i) => centerStart + i), jumpEnd, total]
}