Subj : JSVAL_IS_NUMBER(NaN) == TRUE (!?)
To   : All
From : Rob Swindell
Date : Fri Feb 18 2005 03:21 am

SpiderMonkey oddity:

I found it odd that if jsval is NaN, a test of JSVAL_IS_NUMBER(jsval) would
evaluate as TRUE.

And my native methods don't consider NaN a valid number either, so I needed a
valid test for is number, but non NaN, so I came up with:

#include <jsnum.h>      /* JSDOUBLE_IS_NaN() */

JSBool
jsval_isNaN(JSContext *cx, jsval v)
{
    jsdouble d;

    if(JSVAL_IS_DOUBLE(v)) {
            if (!JS_ValueToNumber(cx, v, &d))
                        return JS_FALSE;
                if(JSDOUBLE_IS_NaN(d))
                        return JS_TRUE;
        }
        return JS_FALSE;
}

// Replacement for JSVAL_IS_NUMBER():
#define JSVAL_IS_NUM(cx,v)      (JSVAL_IS_NUMBER(v) && !jsval_isNaN(cx,v))

I'm surprised there's not something like this already in the jsapi. <shrug>

                                                  digital man

Snapple "Real Fact" #114:
The oldest known animal was a tortoise, which lived to be 152 years old. 

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