isNaN()

isNaN(value): boolean

Checks if value is NaN.

DEPRECATED

Use Number.isNaN() directly instead.

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Parameters

value: unknown

The value to check.

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Returns: boolean

true if value is NaN, else false.

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See Also

• Number.isNaN() - MDN
• Browser support - Can I Use

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Since

2.0.0

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Example

// ❌ Deprecated approach
isNaN(NaN);       // => true
isNaN(0 / 0);     // => true
isNaN(3);         // => false
isNaN(undefined); // => false

// ✅ Recommended approach
Number.isNaN(NaN);       // => true
Number.isNaN(0 / 0);     // => true
Number.isNaN(3);         // => false
Number.isNaN(undefined); // => false