Simple pagination algorithm

simple-pagination.js

function pagination(c, m) {
  const current = c,
    last = m,
    delta = 2,
    left = current - delta + 1,
    right = current + delta + 2,
    range = [],
    rangeWithDots = []
  let l

  for (let i = 1; i <= last; i++) {
    if (i == 1 || i == last || i >= left && i < right) range.push(i)
  }

  for (let i = 0; i < range.length; i++) {
    if (l) {
      if (range[i] - l === 2) rangeWithDots.push(l + 1)
      else if (range[i] - l !== 1) rangeWithDots.push('...')
    }

    rangeWithDots.push(range[i])
    l = range[i]
  }

  return rangeWithDots
}

Make it symmetric.