Simple Pagination (n length)

pagination.js

const pagination = (c, m, n) => {
  let l, r, h, t, x
  if (m <= n) {
    x = Array(m).fill(0).map((x, i) => i)
  } else {
    h = Math.floor(n / 2)
    l = Math.max(0, c - h)
    t = Math.max(0, h - (c - l))
    r = Math.min(m - 1, c + h + t)
    t = Math.max(0, h + t - (r - c))
    l = Math.max(0, l - t)
    x = Array(r - l + 1).fill(0).map((x, i) => i + l)
    if (l !== 0) x = [0, '.', ...x.slice(2)]
    if (r !== m - 1) x = [...x.slice(0, x.length - 2), '.', m - 1]
  }
  return x
}

// let m = 20
// let n = 10
// for (let i = 0; i < m; i += 1) {
// 	console.log(pagination(i, m, n))
// }
// 
// [ 0, 1, 2, 3, 4, 5, 6, 7, 8, '.', 19 ]
// [ 0, 1, 2, 3, 4, 5, 6, 7, 8, '.', 19 ]
// [ 0, 1, 2, 3, 4, 5, 6, 7, 8, '.', 19 ]
// [ 0, 1, 2, 3, 4, 5, 6, 7, 8, '.', 19 ]
// [ 0, 1, 2, 3, 4, 5, 6, 7, 8, '.', 19 ]
// [ 0, 1, 2, 3, 4, 5, 6, 7, 8, '.', 19 ]
// [ 0, '.', 3, 4, 5, 6, 7, 8, 9, '.', 19 ]
// [ 0, '.', 4, 5, 6, 7, 8, 9, 10, '.', 19 ]
// [ 0, '.', 5, 6, 7, 8, 9, 10, 11, '.', 19 ]
// [ 0, '.', 6, 7, 8, 9, 10, 11, 12, '.', 19 ]
// [ 0, '.', 7, 8, 9, 10, 11, 12, 13, '.', 19 ]
// [ 0, '.', 8, 9, 10, 11, 12, 13, 14, '.', 19 ]
// [ 0, '.', 9, 10, 11, 12, 13, 14, 15, '.', 19 ]
// [ 0, '.', 10, 11, 12, 13, 14, 15, 16, '.', 19 ]
// [ 0, '.', 11, 12, 13, 14, 15, 16, 17, 18, 19 ]
// [ 0, '.', 11, 12, 13, 14, 15, 16, 17, 18, 19 ]
// [ 0, '.', 11, 12, 13, 14, 15, 16, 17, 18, 19 ]
// [ 0, '.', 11, 12, 13, 14, 15, 16, 17, 18, 19 ]
// [ 0, '.', 11, 12, 13, 14, 15, 16, 17, 18, 19 ]
// [ 0, '.', 11, 12, 13, 14, 15, 16, 17, 18, 19 ]