[S1764] Using && to determine falsy/truthy in function argument

[PaulSusset]

Getting bug “Identical expressions should not be used on both sides of a binary operator typescript:S1764” when analysing a function call.

Using both sides of “&&” as the same to first make sure the variable is defined (truthy), much like in conditional rendering.

<Component
className={c(
          customClass && customClass
        )}
>

This seems like an acceptable use and could be a false-positive for the rule.

[gab (Gabriel Vivas)]

Hello Paul,

I might be missing something but it seems it would evaluate to the same thing:

• when customClass is falsy, it will evaluate to customClass
• when customClass is truthy, it will evaluate to customClass

In all cases c gets passed the value of customClass.

This is the case in JavaScript and TypeScript, because short-circuits evaluate to the expression value and are not casted to booleans, like in some other languages.

Is there any reason you are not calling c with customClass directly, like c(customClass)?

[PaulSusset]

Hi Gabriel,

That is a great explanation, thank you. I learned something!