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 could sum the values at the same index.

Use: array.reduce(sum)

var sum = (r, a) => r.map((b, i) => a[i] + b);

console.log([[1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12]].reduce(sum));

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