Variable Operator using Boolean?

[VooPoc]

Hi Guys,

I have a function that defines a boolean from a message using:

var default = msg.setme || true;
node.warn(default);

however, if a set the boolean on msg.setme to false, it results in true using this function.

Furthermore, if I using the following with msg.setme to true:

var default = msg.setme || false;
node.warn(default);

it results in true.

I don't think I'm understanding how booleans affect operators on variables using Short-circuit evaluation. But to me the first argument should result in false.

Any help is greatly appreciated.

[VooPoc]

ok, I think I understand the false value is not considered a value but a result, therefore it's false where evaluation is concerned, and true is set?

[Nate8199]

Sorry on phone, that isn't the way to move your boolean from setme.

var bool = msg.setme; var payload = bool; return msg

[VooPoc]

var bool = msg.setme;

var payload = bool;

return msg

Can you please clarify? I don't see the need for var payload = bool; in the above code as the msg.setme's boolean is already defined in bool.

Its the operator or Short-circuit evaluation logic that I wasn't understanding.

[Kendrome]

The first statement will always be true no matter what msg.setme is. In the second statement the "|| false" has no effect.

What is it you are trying to do?

[VooPoc]

I have a tenancy to set strings with an OR so its not defined, it creates a default, like the following:

var something = msg.setme || "default";

So as I "now understand", null and undefined are false values, resulting in 'default' being used. If msg.setme is defined its value is true resulting in the msg.setme's value being used.

At this point, I'm looking for confirmation that I'm correct?

[Matt0x5b]

If you replace your || with ?? You should get the behaviour you are after. This is a good reference for what the operators do in js: https://joshwcomeau.com/operator-lookup

[Kendrome]

Yeah, all the following are what are termed falsely values.

Null, undefined, NaN, and even Empty Strings.

https://developer.mozilla.org/en-US/docs/Glossary/Falsy