How Can I parse out JSON in a Node-RED Function

Question

I am working with Node-RED in Bluemix for IoT.

How can I parse out the individual pieces of information (like the cmdmsg and the tempr) in a function node so I can use it in other nodes in the flow? I'm getting an error when I try (see below)

I am receiving the JSON complete message object (from an IoT in Node) that I see in my "debug" node when I set it to look at the complete message object. see the object below.

It appears to me that the JSON is formatted correctly.

I tried putting the following in the function node, but I'm getting an error that says "TypeError: Cannot read property 'tempr' of undefined"

Here is what the function parameter is: return {payload:msg.payload.d.tempr};

and here is the message object

{
   "topic": "iot-2/type/Arduino-tempsensor/id/FFFFFFFFFFFF/evt/status/fmt/json", 
   "payload": "{\n\"d\": {\n\"myName\": \"Arduino CF\",\n\"cmdmsg\": \"Weekly\",\n\"tempr\": -3,\n}\n}", 
   "deviceId": "FFFFFFFFFFFF", 
   "deviceType": "Arduino-tempsensor", 
   "eventType": "status", 
   "format": "json", 
   "_msgid": "ffffffff.55555" 
}

note: I obfuscated the device ID (mac address) and msgid

Any ideas on how to parse the data out and why I'm getting an error?

Solution

Sorry, but your JSON Payload is completely messed up, it should look like this: {"d": {"myName": "Arduino CF","cmdmsg": "Weekly","tempr": -3}} You shouldn't see any \or \nin the payload, they look like escape characters from the client side. I also believe that the last comma after the tempr value shouldn't be there for valid JSON.

I am not an Arduino expert but I have experimented with a Raspberry Pi and the Mosquitto client, this is how I can successfully send an event to IoTF: mosquitto_pub -h <org>.messaging.internetofthings.ibmcloud.com -p 1883 -u "use-token-auth" -P "<token>" -i d:<org>:raspi:raspi2 -t iot-2/evt/message/fmt/json -m {"d":{"text":"Hello World"}}

If the paylod is correct JSON your statement return {payload:msg.payload.d.tempr}; will work.

Have you seen this: http://www.ibm.com/developerworks/cloud/library/cl-bluemix-arduino-iot2/

Comments

[Henryw4]

Thanks for the input. The payload shown above is when the debug node is set to show the whole message object (which I assume shows the individual formatting including newline characters and such). When I change the debug node to show the payload, I see this: { "d": { "myName": "Arduino CF", "": "CMD", "tempr": -3, } } which looks almost like valid JSON except as you mentioned the comma after the tempr which I will remove and see if that addresses it.

[Henryw4]

yes, the comma at the end was the issue. I had my browser showing everything in small fonts and though that was a period after the temp. Thanks for sort of proof-reading my JSON for me!