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Why is isNaN(null) == false in JS?
The isNan() method is used in JavaScript to check whether there’s the existence of an undefined value or can say checks for a NaN object.
Example
To check whether a JavaScript date is valid or not, you can try to run the following code −
<!DOCTYPE html> <html> <body> <script> var date1, date2; date1 = new Date("2018/1/1"); if( ! isNaN ( date1.getMonth() )) { document.write("Valid date1: "+date1); } else { document.write("<br>Invalid date1"); } date2 = new Date("20181/1"); if( ! isNaN ( date2.getMonth() )) { document.write("<br> Valid date2: "+date2); } else { document.write("<br>Invalid date2"); } </script> </body> </html>
The isNaN(null) == false is semantically correct. This is because null is not NaN.
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