Bug 27611 – document.__proto__ Behavior

• Status: RESOLVED
• Resolution: WONTFIX
• Component: JavaScriptCore

[Joseph Pecoraro]

Please read the comments on this bug report:
https://bugs.webkit.org/show_bug.cgi?id=27169

Note that I'm only concerned with the instanceof.  The typeof doesn't seem to be a major issue.  Which behavior of instanceof do you think is correct?

Summary:

WebKit and Chrome:
> document.__proto__ instanceof window.Node
true
> document.__proto__.__proto__.__proto__ === Node.prototype
true
>typeof document.__proto__
"object"

Firefox:
> document.__proto__ instanceof window.Node
false
> document.__proto__.__proto__.__proto__ === Node.prototype
true
>typeof document.__proto__
"object"

Opera:
> document.__proto__ instanceof window.Node
false
> document.__proto__.__proto__.__proto__ === Node.prototype
ERROR
> typeof document.__proto__
"undefined"

[Keishi Hattori]

Opera doesn7t support __proto__

[Eric Seidel (no email)]

Adding two ECMA experts who would know this off the top of their heads.

[Erik Arvidsson]

This is once again underspecified behavior.

> document.__proto__ instanceof window.Node
true

This is correct because the [[Prototype]] of document should be a Node

> document.__proto__.__proto__.__proto__ === Node.prototype
true

This is less clear. DOM defines everything in interfaces. But given that we treat an interface as a prototype in other places it seems as correct as we can get it

document instanceof HTMLDocument
document.__proto__instanceof Document
document.__proto__.__proto__ instanceof Node

I think this is (or should be) covered by WebIDL.

To me it seems WebKit is doing as good as it can.

[Eric Seidel (no email)]

Any comments as to why the resolution?