Subj : spidermonkey docu
To   : netscape.public.mozilla.jseng
From : Jens Thiele <karme@unforgettable.com>
Date : Wed Apr 07 2004 08:09 am

the JS_ValueToInt32 docu is wrong:
http://mozilla.org/js/spidermonkey/apidoc/gen/complete.html#JS_ValueToInt32

Description
JS_ValueToInt32 converts a specified JS value, v, to a JS double, and
then to a 32-bit integer, if it fits. If the double is out of range,
JS_ValueToInt32 reports an error and conversion fails. The double
rounded to the nearest integer value.

the corresponding source:
js_ValueToInt32(JSContext *cx, jsval v, int32 *ip)
{
    jsdouble d;
    JSString *str;

    if (JSVAL_IS_INT(v)) {
        *ip = JSVAL_TO_INT(v);
        return JS_TRUE;
    }
[...]

=> js_ValueToInt32 does IMHO the right thing ;-)
if it is a JS int value convert to C int32
if not try to convert it to an C int32

.