Add a Timestamp to Function node

General
1

Hi!

I'm using the following flow to read a Modbus power meter Flow 2, this is the string in the function node Function node. I would like to add a time format to the msg.payload.

something like this

{"Time": 2020-03-04 12:15:10}
{"Voltage":228.16}

1 Like
2

Do you mean {"Time": 2020-03-04 12:15:10, "Voltage":228.16} in the payload?
Can I first ask why you want the time as a string rather than a javascript timestamp? Often it is best to keep it as a timestamp and only convert to string when needed for display.

3

Yes that would work too, I'm still learning in node-red. I need the timestamp so i can visualize it in AWS-cloud analytics.

4

That is very easy then, if you pass the message containing a payload of {"Voltage":228.16} to a function node containing

msg.payload.Time = new Date()
return msg;

then that will do it. That assumes you already have the voltage property already setup. If you just have that value as a number in the payload then you can put them both in using

msg.payload = {Time: new Date(), Voltage: msg.payload}
return msg;
1 Like
5

Thanks for the help Colin! it worked for me!

6

Personally, I would output the timestamp in an ISO format because that is easily processed and cannot be misinterpreted but is still human readable.

msg.payload.Time = (new Date()).toISOString()
return msg;

Output looks like: 2020-03-04T15:13:21.294Z

Note that ISO timestamps are always in Zulu timezone (UTC).

7

FYI:

Either way,.... this will often not work and give errors:

[
{"Time": 2020-03-04 12:15:10},
{"Voltage":228.16}
]

The time string needs to be a string, to be sure:

{"Time": "2020-03-04 12:15:10"}

so this will also will have problems, for the same reason:

{"Time": 2020-03-04 12:15:10, "Voltage":228.16}

Should be formatted in JSON as a string, to insure smooth sailing:

{"Time": "2020-03-04 12:15:10", "Voltage":228.16}

Sometimes when having problems (or just building JSON strings), it is a good idea to simply and quickly take your proposed JSON string and copy-and-paste it into some kind of visual editor which will format the JSON.

For example, I use Visual Studio Code, and when I have a JSON string when developing / programming, I quickly copy-and-paste the string into a VSC file with a .json extension and it either formats as a proper JSON string or it does not.

This will often save (us) a lot of time trying to get an API or JSON payload to work when there is some JSON formatting error.

8

How do you know? Does it not depend on where you are sending it? Sending a javascript date may be perfectly valid.
In addition if sending as a string it is often important to include the timezone information.
{Time: new Date()}
does that implicitly.

9

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