Trouble getting the results of a looped subflow to write into an array

General
1

Hi all,

With help from ChatGPT I've created a function node that loops a subflow which reads the present value of a BACnet point. With my function node looping four times, a debug on the output of the subflow shows the four values in the debug window.

However I'm not having any success getting the four values to write into an array. ChatGPT gave me a basic function node takes a bunch of numbers, doubles them, then loads them into a second array which is stored in a flow variable:

// Sample array of numbers
let numbers = [1, 2, 3, 4, 5];
let results = [];

// Loop through the numbers array
for (let i = 0; i < numbers.length; i++) {
results.push(numbers[i] * 2); // Example operation: doubling each number
}

// Store the results in a flow variable
flow.set('double', results);

// Optionally, send the result as a message payload if you want to pass it on in the flow
msg.payload = results;
return null;

My function node contains this (mostly written by ChatGPT):

let results = flow.get('Current') || [];

// Loop through the numbers array
for (let i = 1501; i <= 1504; i++) {

node.send({instance: i});
results.push(msg.payload)

}

// Store the results in a flow variable
flow.set('Current', results);

// Optionally, send the result as a message payload if you want to pass it on in the flow
msg.payload = flow.get('Current');
return null;

The subflow takes the instance i and correctly spits out the present values for analog inputs 1501, 1502, 1503 and 1504. However the flow variable 'Current' in which I want to store those values ends up with what appear to be epoch time stamps in it.

[1738730646869,1738730646869,1738730646869,1738730646869,1738730771309,1738730771309,1738730771309,1738730771309]

Eight values too, not the four I'm generating.

Can anybody spot my problem and advise me?

2

This is where you went wrong:

  1. What is the point of this line? node.send({instance: i});
  2. What does this line do? results.push(msg.payload)
  3. What does msg.payload contain at each iteration of the for loop?

Nothing wrong with using AI to assist you but you do need to understand the code it has written.

3

I assume that you have an inject node connecting to the function node and that inject node is sending a timestamp as msg.payload. If you change the inject node to send a string, you will see that spring replacing the time stamps.

When you have an issue it is wise to provide a simple flow showing the issue.

In order to make code readable and usable it is necessary to surround your code with three backticks (also known as a left quote or backquote ```)

``` 
   code goes here 
```

You can edit and correct your post by clicking the pencil :pencil2: icon.

See this post for more details - How to share code or flow json

4

Thanks zenofmud, I was wondering how to do that.

I actually worked the problem out and now have a working flow. I'd never even looked at ChatGPT until yesterday but it turns out it's quite good at giving you a direction to head in. A lot of adaptation and debugging is needed though.

The resulting flow is attached:

Looping a subflow in Node-Red.txt (9.2 KB)

It uses node-bacnet-contrib-extended to read the BACnet objects, which reside in a Delta eBMGR-2 BMS controller.