Splitting an array of 7, and setting an topic for each message

General
1

Hi

I got an function for splitting an array that contains last 7 days of data ( 0-6), where i want the data for the new day like this:

for (let i = 0; i < msg.payload.length; i++) {
    const el = msg.payload[i];
    const entries = Object.entries(el).map(([key, value]) => ({ topic: key, payload: value }));
    node.send([entries]);
}

The result is 7 messages, but no way to split them to process only the last message in next step

How do i set an topic number (or other key 1-7) for each message or an function for only grabbing msg.payload[6] in the function?

2

You could, but it depends how much work you are prepared to do. :wink:

And as you have written your own node to do it, then you just do what would otherwise be done outside the given split node in that node.

3

Shouldn't be to difficult, but what is the structure of the incoming message, and how do you want the structure of the returned messages?

4

Just take the split node - and with a second switch node - you filter the last message with msg.part.index = 6

5

If you only want the last one - why bother iterate over the array ? just send the last one in the first place ???

1 Like
6

If you mean how can you request one element by using a topic then you can send the payload through a change node to setmsg.payload[msg.topic] to msg.payload

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7

Not sure exactly what you are after but you could do;

As already suggested

const el = msg.payload[6]
const entry = Object.entries(el).map(([key, value]) => ({ topic: key, payload: value }));

return msg

or

for (let i = 0; i < msg.payload.length; i++) {
    const el = msg.payload[i];
    const entries = Object.entries(el).map(([key, value]) => ({ topic: `${key} index ${i}`, payload: value }));
    node.send([entries]);
}

This would give a topic of "key 1" which can be used to select the required msg; or

for (let i = 0; i < msg.payload.length; i++) {
    const el = msg.payload[i];
    const entries = Object.entries(el).map(([key, value]) => ({ topic: key, payload: value }));

    if (i === 6) node.send([entries]);
}

or add a bit to the msg ({ topic: key, payload: value }) becomes ({ topic: key, payload: value, index: i })

Any of these options would allow easy selection of msg 6

8

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