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Use the NaN Value Method in JavaScript
This article mainly introduces how to use the NaN value in JavaScript. It is the basic knowledge in JS learning. For more information, see
NaN, a literal constant without quotation marks, is a special value, indicating that it is not a non-number. Since NaN is always a case of unequal comparison, taking any number, including NaN, is usually an error condition used to indicate that a function with a valid number should be returned.
Note: Use the isNaN () global function to check whether the value is NaN.
Syntax
You can use the following syntax to access properties:
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Var val = Number. NaN; |
Example:
Here, dayOfMonth is allocated with NaN. If it is greater than 31 and a message is displayed, the valid range is:
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<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 produces the following results:
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Day of Month must be between 1 and 31. Value of dayOfMonth: NaN |
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