# Functionnode - extract specific payload data

**URL:** <https://discourse.nodered.org/t/functionnode-extract-specific-payload-data/16559>\
**Category:** General\
**Created:** [10 October 2019 15:49 UTC](https://discourse.nodered.org/t/functionnode-extract-specific-payload-data/16559 "2019-10-10T15:49:34Z")\
**Posts on this page:** 9\
**Page:** 1

<div class="post-metadata">

**Author:** ![Minifugi](https://avatars.discourse-cdn.com/v4/letter/m/bbce88/32.png) [@Minifugi](https://discourse.nodered.org/u/Minifugi)\
**Post date:** [10 October 2019 15:49 UTC](https://discourse.nodered.org/t/functionnode-extract-specific-payload-data/16559/1 "2019-10-10T15:49:34Z")

</div>

Hi!  
Currently trying to wrap my head around node-red and some JS.  
Using the code below I'm able to extract data from my payload.RFID and payload.Key however,  
if none of these payloads exist they both return as "undefined".

```auto
var msg1 = { payload: '{"RFID": "' + msg.payload.RFID+'"}'};
var msg2 = { payload: '{"Key": "' + msg.payload.Key+'"}'};
return [msg1, msg2];

```

How would you prevent this? I figured I could do it with an If statement, but I'm unable to find a working way to check if "msg.payload.RFID" exists?

bonusquestion:  
how do I convert to json directly in the function node? I tried adding a msg3 = JSON.parse(msg1); and then returning msg3 - this didnt work. Currently just using the "json node" to fullfill this.

Attached a picture below showing the outputs, first two messages are with the payloads(correct), two last are when they don't exist(should not output anything).  
 ![nodered](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/2X/4/44e07e16afcf0d730c376830df2dffdad7db1809.jpeg)

Edit:  
Attaching testing flow.

```auto
[{"id":"2f3e2436.82910c","type":"inject","z":"50d2c41c.c2b2fc","name":"All data","topic":"","payload":"{\"ID\": \"52 0B C6 1F\", \"Key\": \"1234\",\"RFID\": \"Mikkel\"}","payloadType":"json","repeat":"","crontab":"","once":false,"x":334,"y":167,"wires":[["5a916d21.8495f4"]]},{"id":"1658c707.976409","type":"debug","z":"50d2c41c.c2b2fc","name":"","active":true,"console":"false","complete":"true","x":1159,"y":137,"wires":[]},{"id":"5a916d21.8495f4","type":"function","z":"50d2c41c.c2b2fc","name":"","func":"key = msg.payload.Key\nrfid = msg.payload.RFID\n\n\nvar msg1 = { payload: {RFID: rfid}};\nmsg2 = { payload: {Key: key}};\nreturn [msg1, msg2];","outputs":"2","noerr":0,"x":631,"y":168,"wires":[["1658c707.976409"],["deaa75af.4cbcd8"]]},{"id":"deaa75af.4cbcd8","type":"debug","z":"50d2c41c.c2b2fc","name":"","active":true,"console":"false","complete":"true","x":1136,"y":197,"wires":[]},{"id":"c4e4ea60.eceda8","type":"inject","z":"50d2c41c.c2b2fc","name":"No RFID","topic":"","payload":"{\"ID\": \"52 0B C6 1F\", \"Key\": \"1234\"}","payloadType":"json","repeat":"","crontab":"","once":false,"x":326,"y":211,"wires":[["5a916d21.8495f4"]]},{"id":"ee0c9741.31c8f8","type":"inject","z":"50d2c41c.c2b2fc","name":"Neither key nor RFID","topic":"","payload":"{\"ID\": \"52 0B C6 1F\"}","payloadType":"json","repeat":"","crontab":"","once":false,"x":288,"y":249,"wires":[["5a916d21.8495f4"]]}]

```

---

<div class="post-metadata">

**Author:** ![bakman2](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bakman2/32/6207_2.png) [@bakman2](https://discourse.nodered.org/u/bakman2)\
**Post date:** [10 October 2019 16:19 UTC](https://discourse.nodered.org/t/functionnode-extract-specific-payload-data/16559/2 "2019-10-10T16:19:55Z")

</div>

Would this work ?

```auto

m = msg.payload

if(m.hasOwnProperty("RFID")){
    
    rfid = msg.payload.RFID
    key = msg.payload.Key
    
    mgs1 = { payload: '{"RFID": "' +rfid+'"}'};
    msg2 = { payload: '{"Key": "' + key+'"}'};
    
    return [msg1, msg2]; 
}

```

You should be able to use `JSON.parse` but not as you describe it, you still would need a `payload` property.  
ie. `msg3 = { payload: JSON.parse(msg1) }`

---

<div class="post-metadata">

**Author:** ![knolleary](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/knolleary/32/3_2.png) [@knolleary](https://discourse.nodered.org/u/knolleary)\
**Post date:** [10 October 2019 16:23 UTC](https://discourse.nodered.org/t/functionnode-extract-specific-payload-data/16559/3 "2019-10-10T16:23:34Z")

</div>

If you don't want these message payloads to be JSON strings, then don't create them as JSON strings. Instead of doing:

```auto
 mgs1 = { payload: '{"RFID": "' +rfid+'"}'};
 msg2 = { payload: '{"Key": "' + key+'"}'};

```

you can do:

```auto
 mgs1 = { payload: {RFID: rfid} };
 msg2 = { payload: {Key: key}};

```

And then there is no need to `JSON.parse` anything.

---

<div class="post-metadata">

**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [10 October 2019 16:38 UTC](https://discourse.nodered.org/t/functionnode-extract-specific-payload-data/16559/4 "2019-10-10T16:38:39Z")

</div>

Curious why you are outputting 2 separate messages. Can't you just use one msg output?

```auto

var rfid = xxxxx;//set me
var key = zzzz;//set me
var mgs1 = { payload: {
    RFID: rfid,
    Key: key
  } 
};
return msg1;

```

That way, one msg is produced and you can access `msg.payload.rfid` and `msg.payload.key` at the same time in the same function/node.

---

<div class="post-metadata">

**Author:** ![Minifugi](https://avatars.discourse-cdn.com/v4/letter/m/bbce88/32.png) [@Minifugi](https://discourse.nodered.org/u/Minifugi)\
**Post date:** [10 October 2019 18:34 UTC](https://discourse.nodered.org/t/functionnode-extract-specific-payload-data/16559/5 "2019-10-10T18:34:20Z")

</div>

@bakman2  
I cant seem to get your code to work, even after fiddling around with it.

Nothing is being returned (sent), So I'm guessing the "hasOwnProperty() doesn't work as expected

@Steve-Mcl  
They're used later on a dashboard and sent to SQL which one was the last entry. This also means  
that they aren't always sent together, so sometimes RFID alone, vice versa.  
Just felt easier to split them here.

Still having issues that if neither of these objects(?) exist they will output "undefined" as payload, and this is then being sent.  
I'm using a change node with ISNULL to \>, but I'd like to see no output from the function node, if neither RFID or Key exists.

---

<div class="post-metadata">

**Author:** ![Minifugi](https://avatars.discourse-cdn.com/v4/letter/m/bbce88/32.png) [@Minifugi](https://discourse.nodered.org/u/Minifugi)\
**Post date:** [10 October 2019 18:35 UTC](https://discourse.nodered.org/t/functionnode-extract-specific-payload-data/16559/6 "2019-10-10T18:35:09Z")

</div>

This works wonders - Thank you!

Still having issues with the "undefined" messages being sent tho.

---

<div class="post-metadata">

**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [10 October 2019 19:03 UTC](https://discourse.nodered.org/t/functionnode-extract-specific-payload-data/16559/7 "2019-10-10T19:03:48Z")

</div>

```auto
mgs1 = { payload: {RFID: rfid} };
msg2 = { payload: {Key: key}};

if(rfid){
  node.send([msg1,null])
}

if(key){
  node.send([null,msg2])
}

```

But you don't really need to send them out of separate pins.

If you use just one output on the function node then...

```auto
if(rfid){
  node.send({ payload: {RFID: rfid}})
}

if(key){
  node.send({ payload: {Key: key}})
}

```

Many ways to skin this cat

---

<div class="post-metadata">

**Author:** ![Minifugi](https://avatars.discourse-cdn.com/v4/letter/m/bbce88/32.png) [@Minifugi](https://discourse.nodered.org/u/Minifugi)\
**Post date:** [10 October 2019 19:22 UTC](https://discourse.nodered.org/t/functionnode-extract-specific-payload-data/16559/8 "2019-10-10T19:22:44Z")

</div>

Oh obviously - way easier than I made it..

I came up with this before your code (yours look simpler tho)  
Is there any explanation to why it saves the messages if I don't declare msg1 and 2?  
(send a payload with both, turns out fine. Send a payload with only one, they both still show up. If you declare msg1&2 this doesn't happen)  
I thought node-red didn't save any data per default?

```auto
var msg1
var msg2

if (msg.payload){

if (msg.payload.hasOwnProperty("RFID")){
    RFid = msg.payload.RFID;
    msg1 = { payload: {RFID: RFid}};
}
if (msg.payload.hasOwnProperty("Key")){
    key = msg.payload.Key;
    msg2 = { payload: {Key: key}};
}
return [msg1, msg2];
}

```

---

<div class="post-metadata">

**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [10 October 2019 19:34 UTC](https://discourse.nodered.org/t/functionnode-extract-specific-payload-data/16559/9 "2019-10-10T19:34:55Z")

</div>

Not sure but if you stick with your code I'd do the following...

```javascript
var msg1, msg2;

if (msg.payload){
  if (msg.payload.RFID)){
    msg1 = { payload: {RFID: msg.payload.RFID}};
  }
  if (msg.payload.Key){
    msg2 = { payload: {Key: msg.payload.Key}};
  }
  return [msg1, msg2];
}

```