On Jun 15, 2011, at 8:51 AM, Allen Wirfs-Brock wrote: > From a posting I made earlier in this thread: > >> Doesn't this new proposal still preclude using proxies to create an exact >> emulation of the built-in Array object type. The "length" property of >> arrays is specified to be non-configurable yet special behavior must occur >> each time the value of length is changed. The proposal would allow "length" >> to be "fixed" as an accessor property whose set behavior did the necessary >> processing. However, that is also a violation of the Array specification as >> it requires that "length" exhibit the attributes of a data property. >> >> I emphasize Array when I look at this simply because it is a fairly simple >> example of the sort of thing that a host object might currently do and the >> most important use case of proxies for me is the replacement/emulation of >> host objects. I really don't know where this idea that non-configurable >> implies no special semantics comes from. That isn't the case in the ES5 >> specification (10.6,15.3.5.4,15.4.5.1+15.4.5.2, 15.5.5.2) for such >> properties.
D'oh, I see. > More generally, for better or worse, Cameron McCormack is right now busily > working to publish the last call draft of a Web IDL specification that > includes rules for what the attribute settings must be for all DOM > properties. If those rules don't match up with what proxies can express then > there will be issues with implementing the DOM in ECMAScript. Paging Dr. Van Cutsem! To emulate length as non-configurable but magically changing its value as a data property may be possible with proxies. It is after all writable. /be _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
