On Tue, Apr 29, 2014 at 7:49 PM, Allen Wirfs-Brock <[email protected]> wrote: > The idea is that a Proxy can define its own property descriptor formats that > it exposes to and accepts form user code. vis > Object.defineProperty/Object.getOwnPropertyDescriptors. This includes the > possibility of new property attributes and censoring built-in attributes.
New property attributes will be useful in fancy metaprogramming, such as glue layers binding JS to other languages with different object models. Proxies already provide plenty of rope for those users without [[Origin]]. They will of course wish to store property metadata in a form other than complete descriptor objects, and they can do that internally. They can even easily provide custom reflection APIs to expose their custom metadata. But [[GetOwnProperty]]'s job is to make those special properties intelligible to the rest of JS, and Object.getOwnPropertyDescriptor's job is to reflect [[GetOwnProperty]]. > For example, you might define a Proxy that exposes something like a typed > array but which did not have any attributes on indexed properties. Well---all properties have attributes. [[GetOwnProperty]] always returns a complete Property Descriptor Record, or undefined. The language relies on it. In that light, you're saying: "you might define a Proxy that exposes something like a typed array but for which the reflection APIs don't work". You might, but why? -j _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
