Private Slots

Kevin Smith khs4473 at
Wed Jan 16 22:57:42 PST 2013

> An explicit goal of ES6 is to support self hosting of important native
> libraries including the DOM. Self hosting libraries will be practical only
> if the self hosted implementation can approach native performance and that
> includes any overhead for branding, where it is required.  In my previous
> message I explained why we shouldn't expect WeakMap based branding, in
> practice, to perform competitively with private Symbol based branding.  If
> we remove private Symbols from ES6 and assume that WeakSymbols aren't a
> perf competitive solution then the only branding solution (for use cases
> like the DOM) that I see remaining is something based upon using Proxies.
> But that would mean that essentially every DOM object would have to be
> represented using a Proxy but proxies themselves impose performance issues
> and currently (using private Symbol branding) most DOM objects don't need
> to be proxies.

I would start by saying that providing a framework for self-hosting the DOM
*with near-native performance* is quite a lofty goal for ES6.  I don't
think that's what the masses are asking for from ES6.

Since this is an argument from performance, I'm going to have to think
carefully about it before I respond.

{ Kevin }
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