ES accessor usage guidelines (Was: Map/Set.prototype.size)

Brendan Eich brendan at
Mon Oct 15 14:39:04 PDT 2012

David Bruant wrote:
> 2012/10/15 Brendan Eich <brendan at 
> <mailto:brendan at>>
>     * get/set accessor may have effects on 'set' (see the DOM) but
>     only on the receiver object (and unobservably,
> I think that "unobservably" will be very hard (if not impossible in 
> most cases) to achieve with proxies.
> "Unobservable except to the receiver handler if the receiver is a 
> proxy" sounds like a more achievable constraint.


>     any children that become garbage, e.g. when trimming .length on an
>     array-like).
> I'm not sure I understand this part. Did you finish your sentence? 
> What does "children" mean here?

No, I meant truncating an array-like by setting .length to 0 may make 
garbage but (absent some weak-ref turn-based notification system) it 
can't be observed.


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