# Handling many JSON msg payload
**URL:** https://discourse.nodered.org/t/handling-many-json-msg-payload/73645
**Category:** General
**Tags:** mqtt
**Created:** [13 January 2023 18:37 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645 "2023-01-13T18:37:13Z")
**Posts on this page:** 11
**Page:** 1
### Author:  [@rchandrashekar53](https://discourse.nodered.org/u/rchandrashekar53)
#### Post date: [13 January 2023 18:37 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645/1 "2023-01-13T18:37:13Z")
Hi, i have multiple MQTT topics and i need to send individual payload at same time to different MQTT topic.
The issue is if i use msg.payload - the JSON frames will be overwritten. I did explore a path where i tried to create msg.test1 and msg.test2 with JSON payload but the issue is how can my MQTT node will not work with this format.
How can i manage this situation.?
code
```auto
[
{
"id": "46a7f55b3dc113fa",
"type": "tab",
"label": "Flow 3",
"disabled": false,
"info": "",
"env": []
},
{
"id": "f90132623ba1efaa",
"type": "inject",
"z": "46a7f55b3dc113fa",
"name": "inject",
"props": [
{
"p": "payload"
},
{
"p": "topic",
"vt": "str"
}
],
"repeat": "1",
"crontab": "",
"once": true,
"onceDelay": 0.1,
"topic": "",
"payload": "",
"payloadType": "date",
"x": 110,
"y": 200,
"wires": [
[
"3120844e6d7228c6",
"08788246c8d75e3e"
]
]
},
{
"id": "3120844e6d7228c6",
"type": "function",
"z": "46a7f55b3dc113fa",
"name": "test1",
"func": "msg.test1={\n\"temperature\" : 20,\n\"pressure\" : 2\n}\n\nreturn msg;",
"outputs": 1,
"noerr": 0,
"initialize": "",
"finalize": "",
"libs": [],
"x": 350,
"y": 160,
"wires": [
[
"7a010a252dc12b7b",
"6264ca3a4d52b995"
]
]
},
{
"id": "08788246c8d75e3e",
"type": "function",
"z": "46a7f55b3dc113fa",
"name": "test2",
"func": "msg.test2={\n\"humidity\" : 89,\n\"load\" : 30,\n\"time\" : \"\"\n}\n\nreturn msg;",
"outputs": 1,
"noerr": 0,
"initialize": "",
"finalize": "",
"libs": [],
"x": 350,
"y": 240,
"wires": [
[
"d806c099180ea2d3"
]
]
},
{
"id": "7a010a252dc12b7b",
"type": "mqtt out",
"z": "46a7f55b3dc113fa",
"name": "",
"topic": "topic1",
"qos": "",
"retain": "",
"respTopic": "",
"contentType": "",
"userProps": "",
"correl": "",
"expiry": "",
"broker": "272c1aebb3ef8a9a",
"x": 610,
"y": 120,
"wires": []
},
{
"id": "d806c099180ea2d3",
"type": "mqtt out",
"z": "46a7f55b3dc113fa",
"name": "",
"topic": "topic2",
"qos": "",
"retain": "",
"respTopic": "",
"contentType": "",
"userProps": "",
"correl": "",
"expiry": "",
"broker": "272c1aebb3ef8a9a",
"x": 590,
"y": 260,
"wires": []
},
{
"id": "6264ca3a4d52b995",
"type": "debug",
"z": "46a7f55b3dc113fa",
"name": "",
"active": true,
"tosidebar": true,
"console": false,
"tostatus": false,
"complete": "test1",
"targetType": "msg",
"statusVal": "",
"statusType": "auto",
"x": 560,
"y": 60,
"wires": []
},
{
"id": "65c1bfd5cb2f1feb",
"type": "debug",
"z": "46a7f55b3dc113fa",
"name": "",
"active": true,
"tosidebar": true,
"console": false,
"tostatus": false,
"complete": "test2",
"targetType": "msg",
"statusVal": "",
"statusType": "auto",
"x": 520,
"y": 320,
"wires": []
},
{
"id": "272c1aebb3ef8a9a",
"type": "mqtt-broker",
"name": "",
"broker": "192.168.1.29",
"port": "1883",
"clientid": "",
"autoConnect": true,
"usetls": false,
"protocolVersion": "4",
"keepalive": "60",
"cleansession": true,
"birthTopic": "",
"birthQos": "0",
"birthPayload": "",
"birthMsg": {},
"closeTopic": "",
"closeQos": "0",
"closePayload": "",
"closeMsg": {},
"willTopic": "",
"willQos": "0",
"willPayload": "",
"willMsg": {},
"sessionExpiry": ""
}
]
```
---
### Author:  [@E1cid](https://discourse.nodered.org/u/E1cid)
#### Post date: [13 January 2023 19:10 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645/2 "2023-01-13T19:10:11Z")
Looking at your functions, your payloads need to be in msg.payload, so you could do.
e.g
```auto
msg.payload = {
"test1": {
"temperature" : 20,
"pressure" : 2
}
}
```
[edit] I am also thinking do you want to join the messages before sending to mqtt out
---
### Author:  [@marcus-j-davies](https://discourse.nodered.org/u/marcus-j-davies)
#### Post date: [13 January 2023 19:13 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645/3 "2023-01-13T19:13:44Z")
Im pretty sure (I don't use MQTT), the MQTT node uses `msg.payload` for the payload.
therefore anything else won't be used.
This is a deep set standard in Node RED.
Try the below.
This will ensure each `payload` is not affecting the other
```auto
[{"id":"f90132623ba1efaa","type":"inject","z":"46a7f55b3dc113fa","name":"inject","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"1","crontab":"","once":true,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":110,"y":200,"wires":[["08788246c8d75e3e"]]},{"id":"08788246c8d75e3e","type":"function","z":"46a7f55b3dc113fa","name":"Send Messages","func":"const Message1 = {\n payload: {\n \"temperature\": 20,\n \"pressure\": 2\n },\n topic: 'topic1'\n}\nnode.send(Message1)\n\nconst Message2 = {\n payload: {\n \"humidity\": 89,\n \"load\": 30,\n \"time\": \"\"\n },\n topic: 'topic2'\n}\nnode.send(Message2)\n\n","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":350,"y":200,"wires":[["d806c099180ea2d3"]]},{"id":"d806c099180ea2d3","type":"mqtt out","z":"46a7f55b3dc113fa","name":"","topic":"","qos":"","retain":"","respTopic":"","contentType":"","userProps":"","correl":"","expiry":"","broker":"272c1aebb3ef8a9a","x":575,"y":200,"wires":[]},{"id":"272c1aebb3ef8a9a","type":"mqtt-broker","name":"","broker":"192.168.1.29","port":"1883","clientid":"","autoConnect":true,"usetls":false,"protocolVersion":"4","keepalive":"60","cleansession":true,"birthTopic":"","birthQos":"0","birthPayload":"","birthMsg":{},"closeTopic":"","closeQos":"0","closePayload":"","closeMsg":{},"willTopic":"","willQos":"0","willPayload":"","willMsg":{},"sessionExpiry":""}]
```
EDIT
i.e as @E1cid explains
---
### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [13 January 2023 19:14 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645/4 "2023-01-13T19:14:24Z")
> [@rchandrashekar53](#):
>
> The issue is if i use msg.payload - the JSON frames will be overwritten.
What makes you say that?
My understanding is that each message is entirely seperate.
---
### Author:  [@marcus-j-davies](https://discourse.nodered.org/u/marcus-j-davies)
#### Post date: [13 January 2023 19:21 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645/5 "2023-01-13T19:21:22Z")
> [@jbudd](#):
>
> My understanding is that each message is entirely seperate.
I _think_ its referring to reusing `payload` when it may still be in transit.
given its an object, its passed as a reference
---
### Author:  [@rchandrashekar53](https://discourse.nodered.org/u/rchandrashekar53)
#### Post date: [13 January 2023 19:33 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645/6 "2023-01-13T19:33:50Z")
thanks Marcus - will try and will keep you posted
---
### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [13 January 2023 19:38 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645/7 "2023-01-13T19:38:34Z")
I admit I'm just making assumptions here, but surely if msg was prone to being overwritten whenever a flow splits into two or more wires we would have heard more people complaining about it?
Can a developer clarify this please?
---
### Author:  [@marcus-j-davies](https://discourse.nodered.org/u/marcus-j-davies)
#### Post date: [13 January 2023 19:45 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645/8 "2023-01-13T19:45:42Z")
Your right, just tested!
it could well be constrained to the function block - as I'm pretty sure I have hit this situation my self.
agreed, confirmation will be nice
---
### Author:  [@E1cid](https://discourse.nodered.org/u/E1cid)
#### Post date: [13 January 2023 20:02 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645/9 "2023-01-13T20:02:53Z")
There was a resent issue regarding not defining vars in function nodes, the result was they were available when the function node was called again. That is if i remember correctly
---
### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [13 January 2023 20:14 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645/10 "2023-01-13T20:14:38Z")
There is [this article](https://nodered.org/blog/2019/09/13/cloning-messages) from @knolleary about a change (in NR 1.0 !) to prevent problems with msg due to pass-by-reference.
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [14 March 2023 20:15 UTC](https://discourse.nodered.org/t/handling-many-json-msg-payload/73645/11 "2023-03-14T20:15:03Z")
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