Javascript: Make sure to understand the question properly. I misunderstood it the first time.

var sum_hourglass_array = [];
var sum;

//k is vertical
//j is horizontal

for (let k=0; k<6; k++){
    let row = arr[k];
    for(let j=0; j<6;j++){
        if ((j+2) <=5 && (k+2)<=5){
            sum = arr[k][j] + arr[k][j+1] + arr[k][j+2] + arr[k+1][j+1] + arr[k+2][j] + arr[k+2][j+1] + arr[k+2][j+2];
            sum_hourglass_array.push(sum);
        }
    } 
}
console.log(Math.max.apply(Math,sum_hourglass_array));