ObjectisNaN

ObjectisNaN is a utility function that was introduced to provide a reliable way of determining whether a value is NaN (Not a Number) in the JavaScript programming language. It is implemented as a static method on the Object constructor, mirroring the style of other Object utility functions such as Object.assign and Object.is. The function accepts a single argument and returns true only when the argument is the primitive NaN value; any other falsy value or non‑numeric type yields false.

The motivation behind ObjectisNaN was to address inconsistencies in the global isNaN function, which coerces its argument to a number before performing the NaN check. This coercion can lead to unintuitive results; for example, isNaN("hello") returns true because the string cannot be converted to a valid number. By contrast, ObjectisNaN(rvalue) strictly checks for typeof rvalue === "number" and rvalue !== rvalue, the latter exploiting the fact that NaN is the only JavaScript value that is not equal to itself.

Implementation got widespread use in polyfill libraries such as core‑js, where it was added as part of the ES2015 feature set for environments lacking native support. Browser compatibility notes indicate that all modern browsers provide Object.isNaN natively, while older versions of Internet Explorer and legacy JavaScript engines rely on the polyfill.

The function’s signature is simple:

Object.isNaN(value)

where the return value is a boolean. It is intended for use in code paths that require precise numeric validation, such as scientific computations, data parsing, and API input validation. Because it only accepts the primitive NaN, developers should be aware that it will return false for wrapper objects like new Number(NaN).