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Unquoted literal constant NaN is a special value representing Not-a-Number. Since NaN always compares unequal to any number, including NaN, it is usually used to indicate an error condition for a function that should return a valid number.
Note: Use the isNaN() global function to see if a value is an NaN value.
You can access this property using the following syntax:
var val = Number.NaN; |
Here dayOfMonth is assigned NaN if it is greater than 31, and a message is displayed indicating the valid range:
<html> <head> <script type="text/javascript"> <!-- function showValue() { var dayOfMonth = 50; if (dayOfMonth < 1 || dayOfMonth > 31) { dayOfMonth = Number.NaN alert("Day of Month must be between 1 and 31.") } alert("Value of dayOfMonth : " + dayOfMonth ); } //--> </script> </head> <body> <p>Click the following to see the result:</p> <form> <input type="button" value="Click Me" onclick="showValue();" /> </form> </body> </html> |
This will produce following result:
Day of Month must be between 1 and 31. Value of dayOfMonth : NaN |
To understand it in better way you can Try it yourself.
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