Square spiral

sspiral.js

const sspiral = (n, step = 1) => {
  const t = Math.sqrt(n) >> 0
  const start = t * t
  let result = []
  if (t % 2)
    if (n - start <= t) result = [-(t - 1) / 2 + n - start, -(t + 1) / 2]
    else result = [(t + 1) / 2, -(t + 1) / 2 + n - (start + t)]
  else if (n - start <= t) result = [t / 2 - (n - start), t / 2]
  else result = [-t / 2, t / 2 - n + (t + start)]
  return result.map(r => r * step >> 0)
}