# Number.isNaN()

The `Number.isNaN()` method determines whether the passed value is `NaN` and its type is `Number`. It is a more robust version of the original, global `isNaN()`.

## Syntax

``Number.isNaN(value)``

### Parameters

`value`
The value to be tested for `NaN`.

### Return value

true if the given value is `NaN` and its type is `Number`; otherwise, false.

## Description

Due to both equality operators, `==` and `===`, evaluating to `false` when checking if `NaN` is `NaN`, the function `Number.isNaN()` has become necessary. This situation is unlike all other possible value comparisons in JavaScript.

In comparison to the global `isNaN()` function, `Number.isNaN()` doesn't suffer the problem of forcefully converting the parameter to a number. This means it is now safe to pass values that would normally convert to `NaN`, but aren't actually the same value as `NaN`. This also means that only values of the type number, that are also `NaN`, return `true`.

## Examples

``````Number.isNaN(NaN);        // true
Number.isNaN(Number.NaN); // true
Number.isNaN(0 / 0);      // true

// e.g. these would have been true with global isNaN()
Number.isNaN('NaN');      // false
Number.isNaN(undefined);  // false
Number.isNaN({});         // false
Number.isNaN('blabla');   // false

// These all return false
Number.isNaN(true);
Number.isNaN(null);
Number.isNaN(37);
Number.isNaN('37');
Number.isNaN('37.37');
Number.isNaN('');
Number.isNaN(' ');
``````

## Polyfill

The following works because NaN is the only value in javascript which is not equal to itself.

``````Number.isNaN = Number.isNaN || function(value) {
return value !== value;
}
``````

## Specifications

Specification Status Comment
ECMAScript 2015 (6th Edition, ECMA-262)
The definition of 'Number.isnan' in that specification.
Standard Initial definition.
ECMAScript (ECMA-262)
The definition of 'Number.isnan' in that specification.
Living Standard

## Browser compatibility

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