Subj : Re: Equivalent of JS_InitClass for global object?
To   : "John J. Lee" <jjl@pobox.com>
From : Brendan Eich <brendan@meer.net>
Date : Sun Aug 24 2003 02:37 pm

John J. Lee wrote:

>Your reply got my mental gears turning on a number of issues, thanks.
>
>One thing I don't understand: The JS_InitClass docs say:
>
>| JS_InitClass builds a class structure, its object constructor, its
>| prototype, its properties, and its methods. A class is an internal JS
>| structure that is not exposed outside the JS engine. You can use a
>| class, its properties, methods, and prototypes to build other objects
>| that are exposed outside the engine.
>
>which seems at first glancce to be in contradiction to your reply:
>

The docs lie, they were written by some Netscape techwriter no longer 
around, who sometimes made up facts (probably frustrated by lack of 
response from engineers who might know -- at the time, I had left the JS 
group I'd founded to co-found mozilla.org).  Sorry about this, it's 
something that should be fixed.

>
>Brendan Eich <brendan@meer.net> writes:
>[...]
>  
>
>>This will work -- you need not call JS_InitClass to use a JSClass
>>struct.  You need to call JS_InitClass only if you have a class
>>constructor, and want it to be named by the class name, and to have a
>>class prototype; or, if you pass null for the constructor, to have the
>>class name denote the class prototype object (e.g., Math).
>>    
>>
>[...]
>
>because, if a class isn't exposed outside the API, why else would one
>want to call JS_InitClass unless one is *required* to call it on *all*
>JSClass structures?
>

That doesn't follow at all.

You can use a statically initialized JSClass struct by passing its 
address to JS_NewObject as the second parameter.  See js.c's 'glob = 
JS_NewObject(cx, &global_class, NULL, NULL);' without any prior or later 
JS_InitClass on that global_class struct.

>I assume there's no reason to require "window" to *really* be the
>global object?
>

There is if you want to run scripts from real-world web pages, 
especially those that know about multiple windows (frames in framesets, 
top-level windows).

/beJohn

.