Erik, Yes, this is exactly what a framework like Prototype would need. Your code is highly reminiscent of Ruby's proposed "refinements" feature [1], one which is being debated for inclusion in Ruby 2.0. If this could be implemented in a way that avoids the dreaded namespace dragons, then I would lobby hard for a feature like this.
Cheers, Andrew [1] http://timelessrepo.com/refinements-in-ruby On Mar 21, 2011, at 3:13 PM, Erik Arvidsson wrote: > The thread about using private names is getting a bit unwieldy but I'd > like to focus on the use case that I have been thinking of as > "Lexically scoped monkey patching" or "Lexically scoped object > extensions" instead of focusing on how to use "private names" to fit > this scenario. > > Extending built ins and modifying existing classes to work around bugs > or to provide a better API is (or was) a common pattern. Today a lot > of JS library shun this approach due to the risk of conflicts. > > Let us assume that you could extend an object in your current lexical > scope and that such extensions could be imported from a module into > your current scope. > > Given: > > { > function largerThanN(obj, n) { > return obj.filter(function(item) { > return item > n; > } > } > > var a = [0, 1, 2, 3, 4]; > print(largerThanN(a, 2)); > } > > Now we would like to make largerThanN to work with Object objects. The > naïve thing to do is to just to add a filter method to > Object.prototype. However, this might cause conflicts with other code > that uses objects. The idea here is that we can do this safely in our > scope (ignore syntax except that it is important that it can be done > statically). > > { > extend Object.prototype with { > filter: function(fun) { > var retval = {}; > for (var key in this) { > if (fun(this[key]) > retval[key] = this[key]; > } > return retval; > } > }; > > function largerThanN(obj, n) { > return obj.filter(function(item) { > return item > n; > } > } > > var a = [0, 1, 2, 3, 4]; > print(largerThanN(a, 2)); > var o = {a: 0, b: 1, c: 2, d: 3, e: 4}; > print(largerThanN(0, 2)); > } > > The above use case cannot be solved using private names because > private names conflict with public names. > > Can we agree that this is a use case that we care about and focus on > this instead of whether private names can or cannot do this? > > -- > erik > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
