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Javascript Number - NaN

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Description:

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.

Syntax:

You can access this property using the following syntax:

var val = Number.NaN;

Example:

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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