On Sat, Apr 17, 2010 at 12:34 PM, Asen Bozhilov <[email protected]> wrote: > Erik Arvidsson wrote: >> >> Unfortunately there are use case (although limited) that cannot be solved >> without a mutable __proto__. Extending built *classes* is one such use case. >> >> function HelloElement() { >> var el = document.createElement('div'); >> el.__proto__ = HelloElement.prototype; >> el.text = 'Hello'; >> return el; >> } >> HelloElement.prototype = { >> __proto__: HTMLDivElement.prototype, >> set text(text) { this.textContent = text; }, >> say: function() { >> alert('Hello'); >> } >> }; >> >> document.body.appendChild(new HelloElement).say(); > > That design is used by some js libraries. Mutable __proto__ allow us to > change prototype chain of created object and safe internal methods of that > object. For example: > > function f() {} > f.__proto__ = { > __proto__ : Function.prototype > }; > > f(); //still have [[Call]] method > new f(); //still have [[Construct]] method > > FuseJS use design like that for augment native objects. > http://github.com/jdalton/fusejs
They really go all-out with that, don't they? But for what reason? I really don't see the point in all that. Then again, I don't see the point in parsing the userAgent string for MSIE, but they do that, too, and apparently something related to somebody else defining an attachEvent. To me, that reminds me of the common question "How do I subclass array in javascript," to which the best answer is "don't." However it looks as if FuseJS is going to prove that it is possible to provide a different answer to that old question. Garrett _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
