isGenerator?

[kevinbarabash]

Not sure if it makes sense to include it in this proposal but it would be nice to have.

[Jamesernator]

Not sure by isGenerator if you mean a generator object or a generator function, both should be possible.

For testing for a generator object the spec defines that all generator objects have a [[GeneratorState]] property, which after initialization must have a value from: "suspendedStart", "suspendedYield", "executing", "completed", so that should be easy to check.

For testing for a generator function its as trivial as checking "[[FunctionKind]]" is equal to "generator".

[hax]

isGenerator may be useful, but we may also need isAsyncFunction isAsyncGenerator or even isBoundFunction isArrowFunction, etc.

I feel we should leave them for future proposals. But maybe we could consider how to make APIs extendable for those future requirements.