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$ curl repovive.com/roadmaps/javascript/variables-data-types/checking-for-nan

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$ curl repovive.com/roadmaps/javascript/variables-data-types/checking-for-nan

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Checking for NaN - Variables & Data Types | JavaScript | Repovive

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JavaScript22 sections · 783 units18h total

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Checking for NaN

The right way

Use Number.isNaN() to check if a value is NaN:

let result = "hello" * 2
console.log(Number.isNaN(result))  // true

There's also a global isNaN() function, but it's unreliable. It converts values first, giving wrong results:

isNaN("hello")         // true (wrong! it's a string)
Number.isNaN("hello")  // false (correct)

Always use Number.isNaN() for accurate checks.