that does not save you from errors when `Object.prototype.get =
function(){}` since `writable` and `get/set` cannot coexist in a descriptor
... a safe approach is to create `var descriptor = Object.create(null);`
and then set its `value` later on before assignment.I remember early discussion with Allen and Brendan about this, the solution was a hybrid [[HasNonObjectProperty]] check so that everything inherited except `Object.prototype` was considered ... although: 1. we have two kind of descriptors, accessors and value descriptors. I don't know who would create classes in order to inherit just a couple of propeties ... like `new WritableButNotConfigurable(value)` ? Has anyone ever seen a piece of code like that? 2. accordingly to point one, descriptors should rather change into `null` objects ASAP and stop this descriptor minefield I am pretty sure nobody expect or desire to work like that Changing that part of the specs iw say easier than defining a new [[HasNonObjectProperty]] pattern, IMO My 2 cents On Thu, May 8, 2014 at 1:25 PM, John-David Dalton < [email protected]> wrote: > ES6 additions like Object.assign use [[OwnPropertyKeys]] for getting the > keys of `source` objects. This helps avoid the method gotchas faced by > developers previously with things like `Object.prototype.writable = true` > and `Object.defineProperty(o, 'foo', { value: 'bar' })`. > > See > https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty#Description(bottom > of section) > > "Bear in mind that these options are not necessarily own properties so, if > inherited, will be considered too. In order to ensure these defaults are > preserved you might freeze the Object.prototype upfront, specify all > options explicitly, or point to null as __proto__ property." > > It's the reason I pre-populate my descriptor attributes with false even > though false is the default. See > https://github.com/lodash/lodash/blob/2.4.1/dist/lodash.js#L112-L117 > > With methods like Object.assign using [[OwnPropertyKeys]] does it make > sense to make things like ToPropertyDescriptor use [[HasOwnProperty]] too. > I think it would be a win for consistency and dev use. > > Thoughts? > > - JDD > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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