Explain what yield does. What does calling .next() return before and after a yield?

Q: Explain what yield does. What does calling .next() return before and after a yield?

`yield` is an operator that can only be used inside generator functions. It pauses the generator's execution and returns the value following `yield` as the `value` property of the `next()` result. When a generator first starts, it runs until the first `yield` or `return`. After the last `yield` or `return`, subsequent `next()` calls return `{ done: true }`.

Difficulty: 5/10

generators, iterator protocol, lazy evaluation

`yield` pauses the generator and returns the following value. Each `next()` returns an object `{ value, done }`; before the first `yield`, the generator hasn't produced a value yet.

yield is an operator that can only be used inside generator functions. It pauses the generator's execution and returns the value following yield as the value property of the next() result. When a generator first starts, it runs until the first yield or return. After the last yield or return, subsequent next() calls return .

Scenario Questions

0-2 years experience

2-5 years experience

1Our codebase uses a generator to lazily read lines from a large file. During a recent bug, .next() started returning undefined after the first yield. What could cause that, and how would you debug it?

Follow-up Questions

Explain what yield does. What does calling .next() return before and after a yield?

Difficulty: 5/10

generators, iterator protocol, lazy evaluation

`yield` pauses the generator and returns the following value. Each `next()` returns an object `{ value, done }`; before the first `yield`, the generator hasn't produced a value yet.

Scenario Questions

0-2 years experience

2-5 years experience

1Our codebase uses a generator to lazily read lines from a large file. During a recent bug, .next() started returning undefined after the first yield. What could cause that, and how would you debug it?

Explain what yield does. What does calling .next() return before and after a yield?

yield pauses the generator and returns the following value. Each next() returns an object { value, done }; before the first yield, the generator hasn't produced a value yet.

Scenario Questions

Follow-up Questions

Explain what yield does. What does calling .next() return before and after a yield?

yield pauses the generator and returns the following value. Each next() returns an object { value, done }; before the first yield, the generator hasn't produced a value yet.

Scenario Questions

Follow-up Questions

`yield` pauses the generator and returns the following value. Each `next()` returns an object `{ value, done }`; before the first `yield`, the generator hasn't produced a value yet.

`yield` pauses the generator and returns the following value. Each `next()` returns an object `{ value, done }`; before the first `yield`, the generator hasn't produced a value yet.