Under the Hood: Loops as Jumps, the Iterator Protocol and a Loop Lab

Maria read a blog post that said for...of is slow, so "always write the index loop". She asks the question she always asks: "But why would it be slow?" Nobody on the team knows, and Kenji has already rewritten three loops. This lesson opens the engine, finds out what a loop really is, and then measures instead of guessing. The answer turns out to be "it depends", and you will see exactly on what.