Comparing a JSON variable to null

[nmattela]

I want to dynamically change the class of a button depending on a condition, in this case the condition is checking whether my variable network-device (a JSON string) is null (as in, the JSON null). I have the following code:

(button
    :class "${network-device == null ? "network-err" : "network-connected"}"
)

But eww doesn't quite understand what I mean by null:

error: No variable named `null` in scope

What would be the proper way to compare a JSON string to the JSON null?
Thanks in advance :)

[w-lfchen]

Try this:

(button
    :class {network-device == "null" ? "network-err" : "network-connected"}
)

Does this work?

[nmattela]

Yes, this does work, but then I am comparing with the string "null" as opposed to the JSON null, no?

[w-lfchen]

I have yet to exhaustively understand the internals of eww, so I can't give a definitive answer.
I think that internally everything is handled as strings and therefore, this is supported by my tests, when using JSON, the null value is the same as the JSON string "null".