Question 242380 in Javascript Question posted in
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Javascript – I'm trying to check if a value is classified as a boolean or not, and i don't understand why my code doesn't work

Check if a value is classified as a boolean primitive. Return true or false.

Boolean primitives are true and false.

function booWho(bool) {
     return bool;
    }
    booWho(null);

This are the tests:

booWho(true) should return true.
Waiting:booWho(false) should return true.
Waiting:booWho([1, 2, 3]) should return false.
Waiting:booWho([].slice) should return false.
Waiting:booWho({ "a": 1 }) should return false.
Waiting:booWho(1) should return false.
Waiting:booWho(NaN) should return false.
Waiting:booWho("a") should return false.
Waiting:booWho("true") should return false.
Waiting:booWho("false") should return false.

My tries:

function booWho(bool) {
      return (bool == true||false)
    }
    booWho(null);

  
    function booWho(bool) {
      return (bool == true|| bool == false)
    }
    booWho(null);

this two gives me a problem with this test: booWho(1) should return false

function booWho(bool) {
      return (bool === true||false)
    }
    booWho(null);

this one gives me a problem with this test: booWho(false) should return true.

I ended up passing with typeof, but i have no idea why the others are giving errors, thanks in advanced

Tags:

3

Answers


  1. 0

    Use strict equality to prevent type coercion and separate the checks to true and false:

    function booWho(bool) {
  return bool === true || bool === false;
}
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  2. 0

    Your last try is close but you need to check for strict equality using a triple equal (===) because non-boolean values can be truthy or falsy as well. === prevents implicit conversion.

    function booWho(bool) {
  return bool === true || bool === false;
}

console.log(booWho(true));
console.log(booWho(false));
console.log(booWho(null));
console.log(booWho([]));
console.log(booWho({}));
console.log(booWho(() => void 0));
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  3. 0

    A slightly more compact version:

    function booWho(bool) {
  return !!bool === bool
}

    You’re checking if coercing bool to a boolean will be of the same value and data type as the original bool value.

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