Redux News Reader

Web Development Full-Stack
1

Hello community,

How on Earth does one know what items are contained in the action payload?

In the Redux News Reader project, he extracts the comments and the articleID from the action payload, and I cannot see how he ascertains that the payload contains a comments item,

https://www.codecademy.com/journeys/full-stack-engineer/paths/fscj-22-front-end-development/tracks/fscj-22-redux/modules/wdcp-22-async-actions-with-middleware-and-thunks-ae945346-91ed-45c4-a7a0-7c98bff0ab99/projects/redux-news-reader

Thanks in advance for the assistance