Consider:
Object.defineProperty(obj, propname, { get: undefined, set: undefined });
Assuming obj has no property named by propname (whether it does or not is
basically irrelevant to this question), the given expression apparently defines
a property with this property descriptor:
{
[[Get]]: undefined,
[[Set]]: undefined,
[[Enumerable]]: false,
[[Configurable]]: false
}
The effect of getting such a property is to return undefined; setting it either
has no effect or throws, depending on the precise code construct being used.
Anyway: what exactly is the meaning of a descriptor whose [[Get]] and [[Set]]
fields are both |undefined|? Merely [[Set]] being |undefined| has a sensible
meaning (readonly yet not necessarily constant property). Merely [[Get]] being
|undefined| makes less sense -- one-way communication with an object via
property setting, rather than by a method call? -- but okay, I can accept it as
plausibly useful. But both [[Get]] and [[Set]] being undefined? I don't see
the purpose or rationale behind it. Could someone enlighten me?
Jeff
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