JavaScript: isNaN

By Xah Lee. Date: . Last updated: .

isNaN is the value of the property key "isNaN" of the Global Object.

console.log(globalThis["isNaN"] === isNaN);

Syntax

isNaN(arg)
Converts arg to number first, and return true if it is NaN, else, false. [see NaN]
console.log(isNaN(NaN));
console.log(isNaN("NaN"));

console.log(isNaN("3") === false);
console.log(isNaN(3) === false);
console.log(isNaN(Infinity) === false);

// all true

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