https://www.codewars.com/kata/521c2db8ddc89b9b7a0000c1/train/javascript

training-on-snail.js

snail = function(array) {
  if (array.length === 0) return []
  if (array.length === 1) return array[0]

  const a = []
  
  let bxi = 0
  let bxe = array[0].length - 1
  let byi = 0
  let bye = array.length - 1

  let r = 0
  let c = 0
  let d = 1
  
  const n = array.length
  
  while(a.length !== n * n) {
    a.push(array[r][c])
    
    if (d === 1 && c < bxe) {
      c++
    } else if (d === -1 && c > bxi) {
      c--
    } else if (c === bxe) {
      r++
    } else if (c === bxi) {
      r--
    }
    
    if (d === 1 && r === bye && c === bxe) {
      d = -1
      bxe--
      byi++
    }
    
    if (d === -1 && r === byi && c === bxi) {
      d = 1
      bxi++
      bye--
    }  
  }
  
  return a
}