Matrix's Diagonal Sum

let matrixExample = [
    [1, 2, 3, 4, 6],
    [4, 5, 6, 5, 6],
    [7, 8, 9, 7, 5],
    [7, 8, 9, 7, 3],
    [7, 8, 9, 7, 3]

];

function sumUpDiagonals(matrix) {
    let n = matrix.length;
    let mainSum = 0;
    let secondarySum = 0;
    for (let i = 0; i < n; i++) {
        mainSum += matrix[i][i];
        secondarySum += matrix[i][n - 1 - i];
    }
    return { mainSum, secondarySum };
}

console.log(sumUpDiagonals(matrixExample));