What is the proper way to return a JSON object to Alexa Smart Home or end AWS Lambda in NodeJS?

Question

I have seen three ways to return a JSON object or end a Lambda function. My trigger is Smart Home Alexa.

1. I am using now is context.succeed(response_JSON);This one works for me. Even if this instructions is inside a nested function. The whole Lambda ends and return the response_JSON to Smart Home Alexa.

2. I have seen in other blogs that say callback(response_error,response_JSON). This one did not work for me. It did not return anything to Smart Home.

3. Others just uses the return response_JSON. I have not used this one.

Answer 1

I am using now is context.succeed(response_JSON);This one works for me. Even if this instructions is inside a nested function. The whole Lambda ends and return the response_JSON to Smart Home Alexa.

context.succeed()/fail() causes the Lambda function to terminate immediately. However, I have not seen this documented in the context object docs, so it may get deprecated in later Node versions (?).

I have seen in other blogs that say callback(response_error,response_JSON). This one did not work for me. It did not return anything to Smart Home.

This one probably doesn't work for you because by default Node.js waits for the event loop to be empty before executing the callback statement. This may be due to open network/database connection. As per the doc, set the context.callbackWaitsForEmptyEventLoop variable to false to send the response right away.

Others just uses the return response_JSON. I have not used this one.

This should be used with async handlers. Read more about async and non-async handlers here: https://docs.aws.amazon.com/lambda/latest/dg/nodejs-handler.html