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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