The literal constant NaN without quotes is a special value, which means it is not a non-number. Since NaN always compares to any number, including NaN, it is usually an error condition used to indicate a function that should return a valid number.
Note: Use the isNaN() global function to see if a value is a NaN value.
Grammar
You can access properties using the following syntax:
var val = Number.NaN;
Example:
Here, dayOfMonth assigns NaN if it is greater than 31 and displays a message 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 the following results:
Day of Month must be between 1 and 31. Value of dayOfMonth : NaN
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