JavaScript is_nan

Returns whether argument is not a number

function is_nan (val) {
    // Returns whether argument is not a number  
    // 
    // version: 1008.1718
    // discuss at: http://phpjs.org/functions/is_nan    // +   original by: Onno Marsman
    // +      input by: Robin
    // *     example 1: is_nan(NaN);
    // *     returns 1: true
    // *     example 2: is_nan(0);    // *     returns 2: false
    var warningType = '';
 
    if (typeof val=='number' && isNaN(val)) {
        return true;    }
 
    //Some errors for maximum PHP compatibility
    if (typeof val=='object') {
        warningType = (val instanceof Array ? 'array' : 'object');    } else if (typeof val=='string' && !val.match(/^[\+\-]?\d/)) {
        //simulate PHP's behaviour: '-9a' doesn't give a warning, but 'a9' does.
        warningType = 'string';
    }
    if (warningType) {        throw new Error('Warning: is_nan() expects parameter 1 to be double, '+warningType+' given');
    }
 
    return false;
}

external links: original PHP docs | raw js source

Examples

» Example 1

Running

1	is_nan(NaN);

Should return

true

» Example 2

Running

1	is_nan(0);

Should return

false

Dependencies

No dependencies, you can use this function standalone.

Open syntax issues

php.js uses JsLint to help us keep our code consistent and prevent some common bugs.

Eventually we want all code to pass or at least take into consideration most fixes suggested by JsLint, following this JsLint configuration we’ve decided on.

Authors

Thanks to the following developers, you get to have is_nan goodness in JavaScript.

Onno Marsman ( original )
Robin ( input )

Comments

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Use:

[CODE]
your_stuff('here');
[/CODE]

for proper code formatting
By submitting code here you are allowing us to use it in php.js hence dual licensing it under the MIT and GPL licenses

Robin
28 Oct '08

I'm sorry I was a douche :(

Onno Marsman
10 Oct '08

Never really thought of using a regular expression to test whether a string would result in an error and you're right: that would probably be a lot better. Feel free to post your suggestion, otherwise I'll have a look at it myself tomorrow.

Furthermore: is_nan in PHP behaves very differently from isNaN in javascript. Javascripts isNaN is more like the opposite of PHPs is_numeric function (Just have a look at the implementation of is_numeric in this library). So a simple wrapper to isNaN won't suffice and the extra check for the number type is needed.

The rest of the code in this function is just to generate errors in the same way PHP does. And the suggested regular expression will, of course, make this code a lot shorter.

Note that is_finite and is_infinite both contain the exact same error code. I will fix this too.

Kevin van Zonneveld
10 Oct '08

@ Robin: I agree that this may look a bit elaborate, but if I remember correctly, Onno Marsman had some very good reasons for implementing it this way. I'll ask him to comment you on the specifics.

Robin
10 Oct '08

... I'm sorry but this is laughable.

isNaN duplicates this functionality. Just write a wrapper.

If you're really bothered, a simple regexp could also do the trick just as easily. This is just getting on the edge of silly now.

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