Mqtt monitoring / syncing states, need bit of help

[Colin]

@krizniq

how logic in Follow node would look like for three topics?

You said you were a confident programmer so I expect you will be able to understand the existing logic in the function node. Javascript is not much different to C or other similar languages. Put a debug node showing the output of the Join node so you can see what comes out of there (and look at the Info tab for that node for an explanation). Also look in the node red docs at the pages on writing functions and on working with messages. First make sure you understand how the flow I posted works, then if you can't see how to extend it to one or three inputs come back and ask.