The parameter of my function, when 1, assumes Boolean value and when False assumes Number value. How do I fix this? Javascript doubt

Question

I’m right at the beginning of my studies with JS, so I got a little lost in this exercise.

I need to type check the single parameter of the 'check' function. When it is True, it returns False and vice versa, for booleans. When it is a Number returns its negation (e.g. 10, resume -10).

But when this parameter is false, it takes the value of a Number, in the case of 0 (and returns -0), when it is 1, it takes the value of a Boolean, in the case of True (and returns False).

I don’t understand why when the parameters are 0 or True, the function runs as expected.

function verifi(par){
    if (par == (true || false)){
        return !par
    } else if((par >= 0) || (par <= 0)){
        return par * (-1)
    } else{
        return "Não encontrado! O parâmetro é do tipo " + typeof par
    }
}

console.log(verifi(0)) //retorna -0, assim como esperado
console.log(verifi(1)) // deveria retornar -1, porém retorna false
console.log(verifi(false)) // deveria retornar true, porém retorna -0
console.log(verifi(true)) //retorna false, assim como esperado

Answer 1

When you do

if (par == (true || false))

you’re actually doing

if (par == true)

When making a comparison using == (equality comparison), some "unwanted" conversions are performed. For example, the following examples print true:

console.log(1 == true);
console.log([1] == true);
console.log("1" == true);

What you probably wanted to have done was used the comparison by identity (===) and use two separate comparisons:

if (par === true || par === false)

or

if (typeof par === "boolean")