JavaScript (ES2026) reference · Number Methods and Properties

JavaScript Number.isNaN() Method

Return true only if a value is the number NaN. Unlike the global isNaN(), it doesn't convert strings first.

JavaScript (ES2026) Since ES2015

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Syntax

Number.isNaN(value)

Parameter	Description
`value`	The value to test.

true or false.

Only NaN is NaNTry it yourself

console.log(Number.isNaN(NaN), Number.isNaN(0 / 0), Number.isNaN("hello"));

Output

true true false

Global isNaN() converts first; NaN never equals itselfTry it yourself

console.log(isNaN("hello"), Number.isNaN("hello"));
console.log(NaN === NaN);

Output

true false
false

Version	Change
JavaScript ES2015	Added

Number.isFinite() · Return true if a value is a finite number. Unlike the global isFinite(), it doesn't convert strings.
isNaN() · Return true if a value is NaN after converting it to a number, so isNaN("hello") is true. Prefer Number.isNaN().
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