max square sum problem (functional)

max_square_sum.js

const neighbours = (pos, transf) => {
  const x = pos[0]
  const y = pos[1]
  return [[x-1, y-1],[x, y-1],[x+1, y-1],[x-1, y],[x,y],[x+1, y],[x-1, y+1],[x, y+1],[x+1, y+1]].map(transf)
}

const maxSumRect = (rows, cols, nums) => {
  const revVirtMatrix = pos => [parseInt(pos / cols), pos % cols]
  const virtualMatrix = pos => (pos[0] * cols + pos[1])
  return nums.reduce((max, val, idx) => {
    const neighboursPosition = neighbours(revVirtMatrix(idx), virtualMatrix)
    if(neighboursPosition.some(x => x < 0 || x > nums.length-1)) return max
    const arraySum = neighboursPosition.reduce((arrSum, i) => arrSum + nums[i], 0)
    return arraySum > max ? arraySum : max
  }, 0)
}

maxSumRect(4, 5, [1,2,-1,-4,-20,-8,-3,4,2,1,3,8,10,1,3,-4,-1,1,7,-6]) // 29