25th of 38 Questions.
How does destructuring and spread (...) use the iterator protocol internally?
Destructuring and spread syntax consume iterables by calling Symbol.iterator and pulling values until done, allowing them to work with any custom iterable.
When you write [a, b, ...rest] = iterable, JavaScript calls iterable[Symbol.iterator]() and reads values until the pattern is satisfied. Similarly, [...iterable] collects all values. This is why you can use spread on Set, Map (with caution), String, and custom iterables.