JavaScript Logic Challenges

[thanhvu85]

How can you check if a variable is NaN (Not-a-Number) in JavaScript without using the isNaN() function?

[Kartikey2011yadav]

Since NaN is the only JavaScript value that is treated as unequal to itself, you can also test if a value is NaN by checking it for equality to itself:

var a = NaN;
a !== a; // true 

[abishek1740P]

You can check if a variable is NaN in JavaScript without using the isNaN() function by using the fact that NaN is the only value in JavaScript that is not equal to itself

function isReallyNaN(value) {
    return value !== value;
}

console.log(isReallyNaN(NaN));       // true
console.log(isReallyNaN(123));       // false
console.log(isReallyNaN("string"));  // false

[queenofcorgis]

Hey there! 👋

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[RexActor]

you can use Object.Is function as well
let value =1; console.log(Object.is(value,NaN));

[luoyerr]

使用String进行比较

function isReallyNaN(value) {
    return String(value) === 'NaN';
} 
console.log(isReallyNaN(NaN));
console.log(isReallyNaN(0 / 0));
console.log(isReallyNaN('abc'));
console.log(isReallyNaN(String));