indexOfMaxSum([[1, 2, 3], [4, 5], [6, 7, 8]]); // 2

indexOfMaxSum([[1, 1, 1], [2, 2], [3]]); // 1

indexOfMaxSum([[1, 5, 1], [2, 2], [3, 1]]); // 0

indexOfMaxSum([[1, 5, 1], [2, 2], [3, 4, 1]]); // 2

function indexOfMaxSum(arr) {

let maxSum =

;

let maxIndex =

;

arr.forEach((subArray, index) => {

const sum = subArray.reduce((acc, val) => acc + val, 0);

if (sum

maxSum)

maxSum = sum;

maxIndex = index;

}

});

return maxIndex;

}