Access number of array

[einfach112]

good Morning,
and again I have a problem with reading out the data that I want to read out.
In the picture I see the result: Payload: array[0]

I would like to respond to that!

e.g. If (the array has the number > 0){
Then do it}
else
{ //do nothing}

so far I have tried with msg.payload.length

I also output the payload length under the name payloadlaenge. The number 81 is there. Why? There should be 0 for comparison.

Where is my mistake in thinking?

Thanks in advance

[E1cid]

if(msg.payload.length === 0){
 do stuff....
}else{
   ... do something else
}

Arrays have a length property you can read about arrays here Array - JavaScript | MDN
[edit fixed typo in length.]
If you wish a function to not output and do nothing return null, you can do this by setting msg = null;

[einfach112]

@E1cid

uff..

thx for your fast replay! i test it ..

[einfach112]

Unfortunately this did not work.
There are only 2 possibilities which can be.
In the first picture the array has a 0
In the second picture the array has a 1

But the payload length never shows me 0 or 1.

[einfach112]

I think the error is that I don't need the length of the payload but the number of objects in the payload's array. Can this be?

To explain the whole thing a little better if necessary:
I check in a database whether a data record already exists or not.

If the data record does not yet exist, I get the following in the debug window:
object
payload: array[0]

In this case the data record should be added.

If the data record already exists I get in the debug window:
object
payload: array[1]
In this case, the data record already exists and nothing needs to be done.

[E1cid]

If you use it correctly it will work
see this example

[{"id":"d949b60aacba0c90","type":"inject","z":"b9860b4b9de8c8da","name":"array length 0","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"[]","payloadType":"jsonata","x":330,"y":140,"wires":[["ee9b01abf97044ae","837e4484190e5395"]]},{"id":"ee9b01abf97044ae","type":"debug","z":"b9860b4b9de8c8da","name":"debug 338","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":450,"y":80,"wires":[]},{"id":"837e4484190e5395","type":"function","z":"b9860b4b9de8c8da","name":"function 21","func":"if(msg.payload.length === 0){\n    msg.payload =\"length 0\";\n}else{\n    msg.payload =\"length 1\";\n}\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":630,"y":140,"wires":[["9d0d9f4b63e71d9b"]]},{"id":"12a8804aedf9931f","type":"inject","z":"b9860b4b9de8c8da","name":"array legth 1","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"[{\"test\":1}]","payloadType":"jsonata","x":330,"y":180,"wires":[["ee9b01abf97044ae","837e4484190e5395"]]},{"id":"9d0d9f4b63e71d9b","type":"debug","z":"b9860b4b9de8c8da","name":"debug 339","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":730,"y":80,"wires":[]}]

Or to do nothing when array length is 1

[{"id":"d949b60aacba0c90","type":"inject","z":"b9860b4b9de8c8da","name":"array length 0","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"[]","payloadType":"jsonata","x":330,"y":140,"wires":[["ee9b01abf97044ae","837e4484190e5395"]]},{"id":"ee9b01abf97044ae","type":"debug","z":"b9860b4b9de8c8da","name":"debug 338","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":450,"y":80,"wires":[]},{"id":"837e4484190e5395","type":"function","z":"b9860b4b9de8c8da","name":"function 21","func":"if(msg.payload.length === 0){\n    msg.payload =\"length 0\";\n}else{\n    msg = null;\n}\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":630,"y":140,"wires":[["9d0d9f4b63e71d9b"]]},{"id":"12a8804aedf9931f","type":"inject","z":"b9860b4b9de8c8da","name":"array legth 1","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"[{\"test\":1}]","payloadType":"jsonata","x":330,"y":180,"wires":[["ee9b01abf97044ae","837e4484190e5395"]]},{"id":"9d0d9f4b63e71d9b","type":"debug","z":"b9860b4b9de8c8da","name":"debug 339","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":730,"y":80,"wires":[]}]

How to import/export a flow

If you require more help please supply a test flow like i have that show the issue you are getting.

[einfach112]

THANK YOU !

IT WORKS!

I have it a little bit changed

if (msg.payload.length === 0) {
    msg.topic = "INSERT INTO eq5q (link) VALUES ('" + msg.payloadpruef + "')";
    return msg;
} else {
    //mach nix
}

[Colin]

Check whether your SQL variant has an INSERT IF NOT EXISTS feature. Using that will be much more efficient.

[E1cid]

If you want to do it that way the else is superflulous, just do

if (msg.payload.length === 0) {
    msg.topic = "INSERT INTO eq5q (link) VALUES ('" + msg.payloadpruef + "')";
    return msg;
}