How do generators handle errors? How does .throw() interact with try/catch inside a generator?

Q: How do generators handle errors? How does .throw() interact with try/catch inside a generator?

function* risky() { try { yield 1; } catch (err) { console.log('caught', err.message); } } const g = risky(); g.next(); g.throw(new Error('boom')); // caught boom

Difficulty: 5/10

error handling, generator control flow, exception propagation

Errors in generators can be caught with try/catch inside the generator. `generator.throw(error)` injects an error at the current yield point, which can be caught by a surrounding try/catch.

Error handling in generators

Scenario Questions

0-2 years experience

1You need a tiny utility that iterates over a generator and logs each value. If the generator hits an error, you want to catch it and keep going. How would you use .throw() and try/catch inside the generator to make that work?
2What will happen if you call gen.throw(new Error('boom')) on a generator that has a try/catch around a yield? Walk me through the control flow.

2-5 years experience

Follow-up Questions

What happens to the generator's internal state after an error is caught?
How does a finally block inside the generator affect .throw() behavior?
Are there any performance concerns when using .throw() frequently in a hot loop?

How do generators handle errors? How does .throw() interact with try/catch inside a generator?

Errors in generators can be caught with try/catch inside the generator. generator.throw(error) injects an error at the current yield point, which can be caught by a surrounding try/catch.

Scenario Questions

Follow-up Questions

How do generators handle errors? How does .throw() interact with try/catch inside a generator?

Errors in generators can be caught with try/catch inside the generator. generator.throw(error) injects an error at the current yield point, which can be caught by a surrounding try/catch.

Scenario Questions

Follow-up Questions

Errors in generators can be caught with try/catch inside the generator. `generator.throw(error)` injects an error at the current yield point, which can be caught by a surrounding try/catch.

Errors in generators can be caught with try/catch inside the generator. `generator.throw(error)` injects an error at the current yield point, which can be caught by a surrounding try/catch.