Why am I getting NaN?

General
1

I am trying to write a function to give me a running average of a sensor value, but no matter what I do, the output is NaN. Yes, I did discover the Mean Value node, so my math is superfluous. Except, I would like to know why I am getting a NaN output- just to learn what I did wrong.

//Put just the average moisture into the payload.
var moistureRaw = msg.moistureRaw;
var runningWet = node.get('runningWet') || 0;
runningWet = (runningWet + moistureRaw ) /2;
node.set('runningWet', runningWet);
msg.payload = runningWet;
return msg;
2 
node.get('runningWet')

There is no node.get function. If you are trying to use the node-scoped context, then use context.get/set.

But I would have expected that to result in an obvious error message in the Debug sidebar telling you node.get is not a function.

3

Actually, my code uses globals, but I changed it at the last moment before posting the question because I knew someone would rail on me for using global.get and global.set for variables not needed in another flow.

So other than that foopas', why is my function sending a NaN? Like I said, the Mean Value node took care of my need to average the sensor readings, but I would like to know what's wrong with my code? (For future knowledge).

//Put just the average moisture into the payload.
var moistureRaw = msg.moistureRaw;
var runningWet = global.get('runningWet') || 0;
runningWet = (runningWet + moistureRaw ) /2;
global.set('runningWet', runningWet);
msg.payload = runningWet;
return msg;
4

It happens if msg.moistureRaw is undefined

5

You are correct. On a previous node I had moved msg.moistureRaw to payload.

Would this:
var moistureRaw = msg.moistureRaw || 0;
resolve an unidentified variable and prevent the NaN error?

(Not for this function, but for future reference).

6

It would with the important caveat that it would only work as you expect with a 0 on the right hand side.

7

There is a function to check whether a value is NaN:

https://www.w3schools.com/jsref/jsref_isnan.asp

1 Like
8

This topic was automatically closed 60 days after the last reply. New replies are no longer allowed.