# 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

### Using isNaN

```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 isNaN(input) {
return typeof input === 'number' && input !== input;
}
```

## Browser compatibility

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Desktop Mobile Server Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Chrome Full support 25 Edge Full support 12 Firefox Full support 15 IE No support No Opera Full support 15 Safari Full support 9 WebView Android Full support ≤37 Chrome Android Full support 25 Firefox Android Full support 15 Opera Android Full support 14 Safari iOS Full support 9 Samsung Internet Android Full support 1.5 nodejs Full support 0.10

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