const maxLength = arr.length;
let max = -Infinity;
let arrAux = Array(3);
let sum = 0;

const getHourglassSum = (arr) => {
  let sum = 0;
  for (let i = 0; i < 3; i++) {
    for (let j = 0; j < 3; j++) {
      sum += arr[i][j];
    }
  }
  sum = sum - arr[1][0] - arr[1][2];
  return sum;
};

for (let i = 0; i < maxLength - 2; i++) {
  for (let j = 0; j < maxLength - 2; j++) {
    arrAux[0] = arr[i].slice(j, j + 3);
    arrAux[1] = arr[i + 1].slice(j, j + 3);
    arrAux[2] = arr[i + 2].slice(j, j + 3);
    sum = getHourglassSum(arrAux);
    if (sum > max) max = sum;
  }
}

console.log(max);