JavaScript Iterators and Generators Quiz

Review

1. What does an iterable provide?

   The iterable interface is defined by Symbol.iterator returning an iterator.
2. Which shape represents an IteratorResult?

   IteratorResult exposes value and done.
3. Why are iterator objects usually described as cursors?

   An iterator carries traversal state and advances through next().
4. What does for...of consume?

   for...of obtains an iterator through the iterable protocol.
5. What does calling a generator function create?

   A generator call returns a generator object that is both iterable and an iterator.
6. What does next(42) do when resuming a generator paused at yield?

   The argument to the resuming next call is delivered to the paused yield expression.
7. What does yield* primarily do?

   yield* delegates the iterator protocol to another iterable.
8. Why can an iterator implement return()?

   Iterator closing can invoke return() so the iterator can clean up.
9. Why are Iterator helpers useful?

   Helpers such as map and filter create lazy iterator pipelines.
10. What is a useful role for Iterator.from?

    Iterator.from wraps an iterable or iterator so modern Iterator methods can be used.
11. What is Iterator.zip()'s default length mode?

    The default mode is shortest.
12. Which option enables padding in Iterator.zip?

    Padding is considered when mode is longest; the padding option supplies values.
13. What does Iterator.zipKeyed use to name properties in each result object?

    The input object’s own keys become the keys of each result object.
14. What iterator hook participates in closing underlying iterators when zip stops early?

    Iterator closing invokes an iterator’s return() method when it provides one.