Negative boolean variable names

[jltwheeler]

Suggestion to explain the best approach for naming negative booleans.

Example: if you create a variable for checking if an object is a dog , you could either do:

const isDog = (dog) => dog.sound() === 'bark'

if (!isDog(pet)) {
    // handle the not dog logic
}

or

const isNotDog = (dog) => dog.sound() !== 'bark'

if (isNotDog(pet)) {
    // handle the not dog logic
}

[kettanaito]

Thanks for the suggestion, @jltwheeler.

I'd suggest going with a positive isDog and negating it when necessary.

const isDog = (dog) => dog.sound() === 'bark'

if (isDog(pet)) {
  // handle a situation when pet is a dog
}

if (!isDog(pet)) {
  // handle a situation when pet isn't a dog
}

I rarely encounter a need for negative boolean variables, so please feel free to reference any examples you see fit.