I was brought in for a 3-hour onsite that consisted of four separate one-hour rounds.

The first round consisted of boarding simple algorithms, followed by lunch with a manager.

The third round was random JavaScript questions from a lead engineer.

The fourth round, and by far the best, was a discussion on what the team was working on, what types of strategies I would use to solve some of the problems they are currently working on, and what level of familiarity I had with their current tech stack.

Write a reduce function, both with and without recursion.