Why doesn't this simple javascript in nodeRED for Visual Flow Creator work?

Question

I'm new to javascript and nodeRED. I'm working in Visual Flow Creator and trying to take 4 values:

var msg = {
    payload: {
        Dryblend_Dose_Finished: true, // Sample values, could be dynamically set
        Filler_Dose_Finished: true,
        Weight_Sent_DryBlend: 100, // Sample values, could be dynamically set
        Weight_Sent_Filler: 50
    }
};

...and when the 2 BOOLean vars are both TRUE, add the 2 "Weight..." values together, storing the result in a new property that will be added to the msg.payload array.

My Code:

// Bring in the payload

var array = msg.payload;

// Check to see if the BOOLs are both TRUE

if (array.Dryblend_Dose_Finished === "true" && array.Filler_Dose_Finished === "true")
{   
    //add the 2 weights together and store for incorporation into the outgoing msg.payload
    array.total = array.Weight_Sent_DryBlend + array.Weight_Sent_Filler;
}
else {
    array.didntWork = 1;
}

// put everything back into the payload

msg.payload = array;

return msg;

It seems to me like this should be "simple" and yet, no matter what I do, it seems like it simply doesn't even run. In my debug node after the function block, I get the same values out that went in with no changes. I added the "didntWork" var thinking I might sanity check my logic, but that doesn't show up either, so now I don't even know if the stupid function is even running (except that nodeRED/Visual Flow Creator says the function completed in 4.08ms.

Anyone have any ideas? This should not be that difficult, and yet this refuses to work.

What am I doing wrong?

Answer 1

The answer has already been given in the comments: Your code is syntactically correct, but there is a problem with your boolean expression. The way you are doing it will never behave as you would expect because you are comparing different types (boolean with string).

The variables Dryblend_Dose_Finished and Filler_Dose_Finished are already booleans, so you don't have to compare them. The boolean expression is as simple as (array.Dryblend_Dose_Finished && array.Filler_Dose_Finished).

Besides that, there are minor issues with your variable names. What you call an array is not really an array in the sense of Javascript. An array looks like this: var pets = ['dog', 'cat', 'rabbit'] and you can access the items via their index like pets[1] (which results in 'cat'). Property payload of object msg is an object itself which consists of the boolean properties Dryblend_Dose_Finished and Filler_Dose_Finished and the numeric properties Weight_Sent_DryBlend and Weight_Sent_Filler. So, naming the variable an array may be misleading. In Javascript it is also a widely adopted to use camelCase naming instead of using '_' as a separator. Your variables would then look like weigthSentFiller or weightSentDryBlend. But not sure if you can influence the format of the message.

In addition, it is good practise to begin names of boolean variables with the verbs is or has like in isFillerDoseFinished or node.hasChildren. Using these naming conventions makes your code better readable and understandable. You would see at the first glance that isFillerDoseFinished is a boolean and that you don't have to check for equality in a boolean expression.

I have tested your code live in Node-RED by using an inject node with the following JSON input as payload:

{
    "Dryblend_Dose_Finished": true,
    "Filler_Dose_Finished": true,
    "Weight_Sent_DryBlend": 100,
    "Weight_Sent_Filler": 50
}

This results in exactly the object that you used in your example (see screenshot debug output before). Then I added a function node with your code, corrected the boolean expression and deployed it. As you can see in the debug output after, the new property total: 150 was added to the payload.

I hope that helps :)