[[Class]] and host objects

Allen Wirfs-Brock Allen.Wirfs-Brock at microsoft.com
Tue Feb 10 18:15:22 PST 2009


>Mark Miller: I like your #2 direction a lot. If it were feasible to require that host objects not even use [[Class]] "Object", I'd be in favor. However, I'm guessing that would differ too greatly from current browser behavior to have a chance.

That's what I thought until I probed around a few DOM objects in IE and Firefox and didn't see any [object "Object"]'s.  We probably need the browser experts to tells whether or not it is common practice to use [[Class]]=="Object" for host objects but a casual inspection looked promising.

From: Mark S. Miller [mailto:erights at google.com]
Sent: Tuesday, February 10, 2009 6:01 PM
To: Allen Wirfs-Brock
Cc: Mark Miller; Brendan Eich; es-discuss
Subject: Re: [[Class]] and host objects

2009/2/10 Allen Wirfs-Brock <Allen.Wirfs-Brock at microsoft.com<mailto:Allen.Wirfs-Brock at microsoft.com>>

Mark Miller said:  We can get the effect of specifying such indistinguishability simply by specifying that host objects may have as their [[Class]] property "Object", or any string not otherwise used by the spec as a [[Class]] value.



I generally agree, but I have two "what about's" that actually go in different directions from each other.



#1 What about "Function" in addition to "Object"? It seems reasonable to have host objects that are functions in addition host objects that are objects. (Counter-argument: slippery slope)



#2 Why allow "Object" for  host objects that are required to conform to the section 15.3 specification for Object. If they are distinguishable from section 15.3 objects they should have [[Class]]=="Object".  An implementation can use "HostObject" or something else. (Counter-argument: Might confuse some programmers??? (seems weak))


I like your #2 direction a lot. If it were feasible to require that host objects not even use [[Class]] "Object", I'd be in favor. However, I'm guessing that would differ too greatly from current browser behavior to have a chance.



--
   Cheers,
   --MarkM
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