AppSync JS resolver do not support the "in" operator?

Question

Hi AWS folks!  I've just been stuck on a failing CloudFormation deployment for a while.  One of my AWS::AppSync::FunctionConfiguration resources was failing with the message `The code contains one or more errors.`.  It is one of the newer JS resolvers types (as opposed to VTL).  After some trial and error, I determined that it was because I was using the [in](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/in) operator.  However, the AppSync [docs](https://docs.aws.amazon.com/appsync/latest/devguide/core-features.html) do not state that this operator is not supported.  Perhaps someone can confirm this and, if I am correct, update the docs?

Answer

Hello, 
I have confirmed from the AWS AppSync team that we do not support the `in` operator in AppSync JS currently. The feedback is shared with our product team and they will work on updating the AppSync documentation. Thank you.

AppSync JS resolver do not support the "in" operator?

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