Sum array of arrays (matrix) vertically efficiently/elegantly

Question

In Javascript, if I have an array of arrays representing a matrix, say

x = [
    [1,2,3,4],
    [5,6,7,8],
    [9,10,11,12]
];

summing it

Answer 1

You can use recursivity to sum arrays of any dimensions with this function:

function sumRecursiveArray(arr) {
  return arr.reduce(function(acc, value) {
    return acc + (Array.isArray(value) ? sumRecursiveArray(value) : value);
  }, 0);
}

var sum = sumRecursiveArray([[1,1,1],[2,2,2]]);
console.log(sum); // 9