How to solve the problem: return the sum of the primary and secondary diagonals of a square matrix?

Design a JavaScript implementation of sumUpDiagonals () to return the sum of the primary and secondary diagonals of a square matrix.
var matrixExample = [ [ 1, 2, 3, 4 ], [ 4, 5, 6, 5 ], [ 7, 8, 9, 7 ], [ 7, 8, 9, 7 ] ]; function sumUpDiagonals(matrix) { // ... } console.log(sumUpDiagonals(matrixExample));
JavaScript Anonymous, Apr 11, 2019 
const sumDiagonals = matrix =>
matrix.reduce((acc, n, i) => {
acc.principal += n[i];
acc.secondary += n[n.length  i  1];
return acc;
}, {
principal: 0,
secondary: 0,
});Anonymous
1 Answers
Your Answer
To place the code, please use CodePen or similar tool. Thanks you!