Subj : Re: SM typeof for extensions
To   : Shanti Rao
From : Brendan Eich
Date : Thu Sep 09 2004 04:50 pm

Shanti Rao wrote:
> Brendan Eich wrote:
>>
>> Is this some evil MS-ism?
> 
> 
> Tee hee. I also have Stream, File, ODBC, and Mail classes. ActiveX was 
> just first on the list.


Wait, I was asking whether you were emulating something JScript does. 
If you're just looking for a way to distinguish classes of objects, then 
don't use typeof -- see below.


>> With E4X, there may be a general way to change the result of typeof. 
>> Right now, you'll have to hack jsapi.c.  Gross.
> 
> 
> My workaround is to give the prototype a "className" property. Does 
> anyone else want to suggest a convention for solving this?


The standard has always been, for SpiderMonkey, to test using

   typeof o == "object" && o != null

to decide that o is an object reference, and then to use

   o.constructor

or (SM and Rhino(?) only, an ECMA extensions):

   o.constructor.name

to identify the object's class by its constructor function or 
constructor function name, respectively.

/be

.