Number.isNaN()

The Number.isNaN() static method determines whether the passed value is the number value NaN, and returns false if the input is not of the Number type. It is a more robust version of the original, global isNaN() function.

The function Number.isNaN() provides a convenient way to check for equality with NaN. Note that you cannot test for equality with NaN using either the == or === operators, because unlike all other value comparisons in JavaScript, these evaluate to false whenever one operand is NaN, even if the other operand is also NaN.

Since x !== x is only true for NaN among all possible JavaScript values, Number.isNaN(x) can also be replaced with a test for x !== x, despite the latter being less readable.

Syntax example: Number.isNaN(value)