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JavaScript isNaN() Function

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  • Last Updated : 02 Dec, 2021

The isNaN() function is used to check whether a given value is an illegal number or not. It returns true if value is a NaN else returns false. It is different from the Number.isNaN() Method.

Syntax:

isNaN( value )

Parameter Values: This method accepts single parameter as mentioned above and described below: 
 

  • value: It is a required value passed in the isNaN() function.

Return Value: It returns a Boolean value i.e. returns true if the value is NaN else returns false.

Javascript




<script>
    document.write(isNaN(12) + "<br>");
    document.write(isNaN(0 / 0) + "<br>");
    document.write(isNaN(12.3) + "<br>");
    document.write(isNaN("Geeks") + "<br>");
    document.write(isNaN("13/12/2020") + "<br>");
    document.write(isNaN(-46) + "<br>");
    document.write(isNaN(NaN) + "<br>");
</script>

Output:

false
true
false
true
true
false
true

Supported Browsers:

  • Chrome 1 and above
  • Firefox 1 and above
  • Edge 12 and above
  • Opera 3 and above
  • Safari 1 and above
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