JavaScript isNaN()
Example
Check if a value is NaN:
isNaN(123);
isNaN(-1.23);
isNaN(5-2);
isNaN(0);
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isNaN('123');
isNaN('Hello');
isNaN('2005/12/12');
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More examples below.
Definition and Usage
In JavaScript NaN is short for "Not-a-Number".
The isNaN() method returns true if a value is NaN.
The isNaN() method converts the value to a number before testing it.
See Also:
Difference Between isnan() and Number.isnan()
isNaN() method returns true
if a value is Not-a-Number.
Number.isNaN() returns true
if a number is Not-a-Number.
In other words:
isNaN() converts the value to a number before testing it.
Examples
// This returns true;
isNaN('Hello');
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// This returns false;
Number.isNaN('Hello');
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Syntax
isNaN(value)
Parameters
| Parameter | Description |
| value | Required. The value to be tested. |
Return Value
| Type | Description |
| A boolean | true if the value is NaN, otherwise
false. |
More Examples
Check if a value is NaN:
isNaN(0/0);
isNaN('');
isNaN('A');
isNaN(true);
isNaN(false);
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isNaN('NaN');
isNaN(NaN);
isNaN(undefined);
isNaN(null);
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Browser Support
isNaN() is an ECMAScript1 (ES1) feature.
ES1 (JavaScript 1997) is fully supported in all browsers:
| Chrome | Edge | Firefox | Safari | Opera | IE |
| Yes | Yes | Yes | Yes | Yes | Yes |
