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JavaScript isNaN() Function
JavaScript Global Functions
Definition and Usage
The isNaN() function determines whether a value is an illegal number (Not-a-Number).
This function returns true if the value is NaN, and false if not.
Syntax
isNaN(value)
| Parameter | Description |
|---|---|
| value | Required. The value to be tested |
Browser Support
The isNaN() function is supported in all major browsers.
Example
Example
Check whether a number is an illegal number:
<script type="text/javascript">
document.write(isNaN(123)+ "<br />");
document.write(isNaN(-1.23)+ "<br />");
document.write(isNaN(5-2)+ "<br />");
document.write(isNaN(0)+ "<br />");
document.write(isNaN("Hello")+ "<br />");
document.write(isNaN("2005/12/12")+ "<br />");
</script>
document.write(isNaN(123)+ "<br />");
document.write(isNaN(-1.23)+ "<br />");
document.write(isNaN(5-2)+ "<br />");
document.write(isNaN(0)+ "<br />");
document.write(isNaN("Hello")+ "<br />");
document.write(isNaN("2005/12/12")+ "<br />");
</script>
The output of the code above will be:
false
false
false
false
true
true
false
false
false
true
true
Try it yourself »
JavaScript Global Functions
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Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content.
While using this site, you agree to have read and accepted our terms of use and privacy policy.
Copyright 1999-2012 by Refsnes Data. All Rights Reserved.
Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content.
While using this site, you agree to have read and accepted our terms of use and privacy policy.
Copyright 1999-2012 by Refsnes Data. All Rights Reserved.