Fail in the first question

[yitsushi]

Currently,

var result = [[0, 1], [2, 3], [4, 5]].reduce(function(a, b) {
  return a.concat(b.reverse());
});
console.log(result);

And the right answer for that is:

[ 0, 1, 3, 2, 5, 4 ]

Because you did not defined the initial value.

The right answer as the question asked would be: [ 1, 0, 3, 2, 5, 4 ]

To reach this you need to initialize the "memo" as an empty array:

var result = [[0, 1], [2, 3], [4, 5]].reduce(function(a, b) {
  return a.concat(b.reverse());
}, []);
console.log(result);

Fix the question or the answer please :)

[gergelyke]

Could you send a PR please?

[yitsushi]

Yes if you tell me what do you want. Fix the answer of fix the question.

[gergelyke]

Your call