Do we really need the [[HasOwnProperty]] internal method and hasOwn trap

Allen Wirfs-Brock allen at wirfs-brock.com
Mon Nov 12 10:17:06 PST 2012


On Nov 12, 2012, at 2:21 AM, Brandon Benvie wrote:

> Shouldn't it be the reverse, based on the removal of getPropertyDescriptor/Names? The proxy controls what i's [[Prototype]] is which indirectly directs how non-own lookups proceed. The functionality of `has` can (and usually should) be derived from proto-walking hasOwn until true or null.

yes, that would be a good fix for this particular problem.  [[HasOwnProperty]] could remain as an internal method and HasProperty could be defined as an abstraction operation that uses the [[Prototype]] internal accessor and [[HasOwnProperty]].

Another potential consistency issue is between [[HasOwnProperty]] and [[GetOwnProperty]].  That could be eliminated by combining them into one operation:

[[GetOwnPropety]](name, descriptorNeeded) -> descriptor | boolean | undefined

If descriptorNeeded is true it acts as the current [[GetOwnProperty]]. If descriptorNeeded is false it acts as the current [[HasOwnProperty]].

At the handler-level it makes it impossible to override "hasOwn"without also overriding "getOwnPropertyDescriptor"

Allen




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