Le 04/05/2012 18:37, Allen Wirfs-Brock a écrit : > > On May 4, 2012, at 8:33 AM, David Bruant wrote: > >> Hi, >> >> Le 04/05/2012 06:42, Allen Wirfs-Brock a écrit : >>> Common ways to configure the global environment: >>> >>> Browser compat: >>> ES5 built-in global bindings replicated on the global object >>> any new ES6 built-in global bindings are not replicated on >>> the global object >> I disagree with this point as it makes web browsers inconsistent. >> Some code does feature detection by testing presence on the global >> object (since it's currently equivalent to "typeof builtinGlobalName >> !== 'undefined'"). You're saying that the equivalent should be >> broken, so, ES5 and ES6 features won't be feature-detectable the same >> way. >> I don't think there is a loss in having ES6 built-in global bindings >> replicated on the global object. Actually, Firefox does define >> WeakMap and Map as global object properties. > > "typeof builtinGlobalName" doesn't change in anything I proposing here. I understand, but "'WeakMap' in this" or "'WeakMap' in window" is something people will use. That's a way of doing feature detection as well.
> From the perspective of ES code and identifier resolution there is > simply a single global lexical contour that includes all built-ins, > top-level declarations, and properties of the global object. The > "sub-environments" I'm talking about is simply a means to define the > interactions between language induced bindings and properties of the > global object (if there is one). It isn't at all clear to me why > WeakMap, Map, or any other future ES global binding should be > polluting the property name space of the DOM window object. It isn't to me either why 'Array' pollutes the DOM window object, but that's how it's been implemented. > Why is referencing window.WeakMap a good idea? >From an absolute standpoint, I don't think it is, we agree on that. But it would just make new features consistent with old features. For a newcomer to the language 15 years from now, it will be inconsistent to realize that for built-ins, some identifier have a global object property counterpart and some don't. The only reason that makes a "WeakMap" global object property a "good idea" is consistency. That's also how it's currently implemented in Firefox and Chrome. Acknowledging that built-in identifiers are aliased as global object properties in web browsers, what is the downside of continuing? David _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
