A few years late, but for others that are wondering, in vscode just typing /** and hitting enter will create a comment block

You're logging things to the console, aren't you? Don't.

6, the first till is used by 1 and 3 and the second for 2 and 4. 2 + 4 = 6.

The sort is going to be the slowest part. An extra iteration does not make a difference in regards to time complexity.

Regardless, your solution also iterates over the array twice while sorting.
Your solution is also potentially much slower since you put the sort inside the map. Depending on the compiler, your time complexity could be much worse.

I actually wrote them by hand... It doesn't take that long to be honest.

Yeah, changing an array is almost always a bad idea, but Array.filter() doesn't do that: it returns a new array.

Using a counter would be a great approach, since it never incurs the overhead of creating a new array. On the other hand, filter is parallelizable, so it might end up still being faster in practice!

One way to square both approaches would be to use Array.reduce() to have a counter and avoid changing the original array.

Thanks for the suggestion!