Function node vs change node. I'm missing something

General
1

(look at my name)

This flow:

[{"id":"35d675e4.2ad77a","type":"function","z":"184dc884.7aba5f","name":"","func":"delete msg.payload;\nmsg.payload.COMMAND = \"Command\";\nreturn msg;","outputs":1,"noerr":0,"x":220,"y":3430,"wires":[[]]},{"id":"633c46c.32c0438","type":"inject","z":"184dc884.7aba5f","name":"","topic":"","payload":"blah","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":80,"y":3390,"wires":[["35d675e4.2ad77a","7baa8ebf.dbb1c8"]]},{"id":"7baa8ebf.dbb1c8","type":"change","z":"184dc884.7aba5f","name":"","rules":[{"t":"delete","p":"payload","pt":"msg"},{"t":"set","p":"payload.command","pt":"msg","to":"This is the command","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":250,"y":3390,"wires":[["66d94b85.c264bc"]]}]

Via the change node it works. (learned what has been said)

For the sake of trying I thought I did the same in the function node.

This is in the node:

delete msg.payload;
msg.payload.COMMAND = "Command";
return msg;

Pressing the inject I get this:

TypeError: Cannot set property 'COMMAND' of undefined

Shrug.
I'm seriously missing something.

2

delete msg.payload deletes ‘payload’ frpm the msg object. Since payload no longer exists, you can’t set payload.command to anything since payload does not exist..

You should be able to say `msg.payload = {“COMMAND”:”Command”}

3

But to me that is exactly what the change node is doing.

I delete msg.payload (Ok, that didn't work as I thought with formatting)
and then set the msg.payload.command to the text.

Where's the elephant?

Screenshot from 2020-01-27 10-49-26

4

The Change node automatically creates missing objects in the property hierarchy ... As I believe I said in your previous thread about the change node.

5

Andrew think of it this way. A change node does things behind the covers to make life easier for you but you are constrained by the actions the node will allow you. On the other hand, with a function node you have to do all the work, but you have all the control to do what you want...as long as it is valid javascript.

6

Thanks Nic. I am not trying/wanting to be difficult.

I am probably just at "information overload" just now.

7

Thanks.

I am really not having a good time just now with information up take.

I think I had better take a break from it and clear my head.

8

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