RE: "var" declarations shadowing properties from Window.prototype

> From: Cameron McCormack [mailto:cam@mcc.id.au]
> 
> Brendan Eich:
> > As noted, they started out that way 17 years ago. I think WebIDL and
> > interface-based method definition made onload, e.g., predefined on
> > window objects, or more recently on Window.prototype. Was this useful?
> > Was it intended specifically (for window, not just intended generally
> > due to WebIDL's uniform rules for binding its definitions in JS)?
> 
> I don't think it provides any benefit.  Uniformity is the only reason the spec
> says they should be there, currently.

It does provide the monkey-patch benefit for "shared" interfaces (e.g., those shared by inheritance). At the present time, the only one I can think of that [will] act like this is EventTarget (IE10 hasn't yet implemented this hierarchy change).