paginate

1interface PaginateProps {
2  currentPage: number;
3  totalPages: number;
4  siblings?: number;
5}
6 
7const range = (start: number, end: number) => {
8  return Array.from({ length: end - start }, (_, i) => i + start);
9};
10 
11const between = (num: number, min: number, max: number) => {
12  return Math.max(min, Math.min(num, max));
13};
14 
15export const paginate = ({
16  currentPage,
17  totalPages,
18  siblings = 2,
19}: PaginateProps) => {
20  const page = between(currentPage, 1, totalPages);
21  const max = totalPages - 1;
22 
23  const left = between(
24    page - siblings,
25    2,
26    Math.min(max - siblings * 2 - 1, max),
27  );
28  const right = between(
29    page + siblings,
30    Math.min(2 + siblings * 2 + 1, max),
31    max,
32  );
33 
34  const hasLeftEllipsis = left - 1 > 2;
35  const hasRightEllipsis = totalPages - right > 2;
36 
37  const middle = range(
38    left - 1 === 2 ? left - 1 : left,
39    totalPages - right === 2 ? right + 2 : right + 1,
40  );
41 
42  const items = [
43    { type: "item", value: 1 },
44    ...(hasLeftEllipsis
45      ? [
46          {
47            type: "ellipsis",
48            value: between(page - siblings * 2 - 1, 1, totalPages),
49          },
50        ]
51      : []),
52    ...middle.map((n) => ({ type: "item", value: n })),
53    ...(hasRightEllipsis
54      ? [
55          {
56            type: "ellipsis",
57            value: between(page + siblings * 2 + 1, 1, totalPages),
58          },
59        ]
60      : []),
61    ...(totalPages >= 2 ? [{ type: "item", value: totalPages }] : []),
62  ];
63 
64  return {
65    prev: page > 1 ? page - 1 : null,
66    next: page < totalPages ? page + 1 : null,
67    current: page,
68    items,
69  };
70};
71 
72export type PaginateReturn = ReturnType<typeof paginate>;