Just curious: why did you need a nominal type test, rather than a "duck
type" test?
/be
Irakli Gozalishvili wrote:
Hi,
Today I had to deal with a value type detection in JS and that
reminded me of all the pain associated with it, especially when
dealing with values that may have come across the diff compartment /
frame / context. `instanceof` is useless when dealing with objects
from diff contexts, `typeof` is also pretty limited in a sense that it
can detect weather value is array, error, map, set, etc.. not to
mention it's awkwardnesses…
Only solution that seems to work toady that is adopted by most popular
JS libraries is:
function type(value) {
return Object.prototype.toString.call(value).split('
')[1].split(']')[0].toLowerCase()
}
I don't actually know if that's supposed to work according to spec or
if it's just an implementation coincidence that happen to
work. Either way I would really welcome some standard
solution preferably via function form (so that can be polyfilled today)
to do type detection for all the built-ins and host objects.
Aside main issue, it would be great if solution was compatible with
mozilla's xpcom components too where one object my be
queried with multiple interfaces and there for have multiple types.
Also, above hack does not works with XPCOMs as
Object.prototype.toString returns "[object
XPCWrappedNative_NoHelper]", while actual toString returns something
little more useful "[xpconnect wrapped (nsISupports, nsIURI, nsIURL)]"
Regards
--
Irakli Gozalishvili
Web: http://www.jeditoolkit.com/
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