What happens if you forget to return { done: true } in a custom iterator? What are the consequences?

Q: What happens if you forget to return { done: true } in a custom iterator? What are the consequences?

If a custom iterator never returns `{ done: true }`, constructs that consume iterators (e.g., `for...of`, `Array.from`, spread `...`) will continue calling `next()` indefinitely, causing an infinite loop. This can freeze the program or crash due to memory exhaustion. Always ensure the iterator eventually signals completion.

Difficulty: 5/10

iterators, generator protocol, resource cleanup

Forgetting `{ done: true }` causes infinite loops in constructs like `for...of`, as they never receive a termination signal, leading to an infinite loop or memory exhaustion.

If a custom iterator never returns { done: true }, constructs that consume iterators (e.g., for...of, Array.from, spread ...) will continue calling next() indefinitely, causing an infinite loop. This can freeze the program or crash due to memory exhaustion. Always ensure the iterator eventually signals completion.

Scenario Questions

0-2 years experience

2-5 years experience

1During a code review you notice a generator that yields values but never returns { done: true }. The feature hangs when used in a pagination component. How would you debug and fix it?

Follow-up Questions

What happens if you forget to return { done: true } in a custom iterator? What are the consequences?

Difficulty: 5/10

iterators, generator protocol, resource cleanup

Forgetting `{ done: true }` causes infinite loops in constructs like `for...of`, as they never receive a termination signal, leading to an infinite loop or memory exhaustion.

Scenario Questions

0-2 years experience

2-5 years experience

1During a code review you notice a generator that yields values but never returns { done: true }. The feature hangs when used in a pagination component. How would you debug and fix it?

What happens if you forget to return { done: true } in a custom iterator? What are the consequences?

Forgetting { done: true } causes infinite loops in constructs like for...of, as they never receive a termination signal, leading to an infinite loop or memory exhaustion.

Scenario Questions

Follow-up Questions

What happens if you forget to return { done: true } in a custom iterator? What are the consequences?

Forgetting { done: true } causes infinite loops in constructs like for...of, as they never receive a termination signal, leading to an infinite loop or memory exhaustion.

Scenario Questions

Follow-up Questions

Forgetting `{ done: true }` causes infinite loops in constructs like `for...of`, as they never receive a termination signal, leading to an infinite loop or memory exhaustion.

Forgetting `{ done: true }` causes infinite loops in constructs like `for...of`, as they never receive a termination signal, leading to an infinite loop or memory exhaustion.