[
["a", "b", "c"],
["A", "B", "C"],
["1", "2", "3"]
].reduce(
function (a, e) {
return [
a[0] + e[0],
a[1] + e[1],
a[2] + e[2]
];
}, ['', '', ''] // initial copy of the accumulator, passed to reduce()
);
// --> ["aA1", "bB2", "cC3"]