Brendan Eich brendan at mozilla.com
Thu Nov 17 14:15:24 PST 2011

On Nov 17, 2011, at 2:08 PM, David Herman wrote:

>> Prototype extension or delegation is not the same as FRU at all -- the delegating object can shadow proto-properties,
> That's precisely what makes it analogous to FRU. You functionally update (i.e., update without mutating) by shadowing.

Mutating [[Prototype]] is still mutation :-P.

The fact that you get a chain of two or more objects instead of one is the big thing about this that makes it not FRU to me. We don't have records, of course, but squinting hard at objects might make them look as pretty (need beer goggles ;-). But only own properties of a single object, so I'd want FRU of this kind:

let o = { p:1, r:3 };
let u = { o where p:1, q:2 };

and u would have own p, q, and r.


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