answering inline ... On Fri, Feb 27, 2015 at 2:22 PM, Andri Möll <[email protected]> wrote:
> noone? JSLint doesn't even let you write a for/in loop if you don't have > `obj.hasOwnProperty(key)` in it, and usually nobody wants inherited > properties (included methods from old classes/ahem prototypes) reassigned > everywhere. > > > Huh? Old prototypes? Those prototypes have their properties set as > non-enumerable since how long now? > nope, I was rather talking about user-land defined "classes" through prototypes. in ES3 these are all enumerable, you don't want methods copied all over your objects each time because that's the entire point of having prototypal inheritance, right? If instead of inheriting and composing you copy everything as enumerable, writable, and configurable, that's your choice, not what I believe we all need. > You yourself said one shouldn’t use Object.assign for objects with > behavior in the inheritance chain. And I agree. It’s pretty much only > useful for data objects (a.k.a plain). Those have no methods in the > inheritance chain one needs to ignore. > meaning you are good to go with assign or the function I wrote for you. > > Again, I ask, *what is the problem to which ignoring inherited properties > is the solution to?* > > [ 1 ] What is the problem in accessing inherited values? If you don't want to distinguish them, just don't and use a for/in Why do you want now to change Object assign instead of simply using for/in? This requirement is available since 1999 > I posit everyone wants inherited properties. Just half of the people have > been FUDed into being afraid of inheritance. But arguments based on > assumptions on what other people want are irrelevant because naive people > are easy to influence. > You seem to be afraid of inheritance since you want to ignore it and flat all the properties per each copied/enriched object. I am back with previous [ 1 ] question then. > JSLint is how Douglas Crockford writes his code. That’s not an argument > for right APIs. JSON.stringify is equally retarded with its inconsistent > handling of inheritance, but that’s another matter. > You can define you r`toJSON` method that returns the result of the for/in based function I've written for you. Is that retarded? Moreover, you can recreate instances at parse time with a specialized reviver: https://gist.github.com/WebReflection/87e41c09691edf9432da Is that retarded? ( maybe this one is :P ) > > And as I said below: until everyone also prefixes their obj.name uses > with hasOwn: `*obj.hasOwnProperty(“name”) && obj.name <http://obj.name>`*, > skipping inherited properties is a fool’s errand. It causes *inconsistent > APIs* because you don’t run your options et alii objects through > inheritance strippers every time. And you shouldn’t. Or does anyone > disagree with that? > actually, following your logic you should never access that unless you are sure it's also enumerable so ... `*obj.hasOwnProperty("name")** && **obj.propertyIsEnumerable("name") && **obj.name <http://obj.name/>`*` > > This is a bigger problem than my use of Object.assign. Proliferation of > Object.assign will prevent everyone else from relying on inheritance. And > in a prototypal language I find that bad API design. > Precisely ! So use inheritance instead of flattening/hiding it everywhere. Use dictionaries and for/in when all this does not matter. I really don't see, with all possibilities you have to write the way you want, and a function I wrote for you that does what you need, why bothering `Object.assign` Best Regards > > A. > > On Feb 27, 2015, at 15:40, Andrea Giammarchi <[email protected]> > wrote: > > noone? JSLint doesn't even let you write a for/in loop if you don't have > `obj.hasOwnProperty(key)` in it, and usually nobody wants inherited > properties (included methods from old classes/ahem prototypes) reassigned > everywhere. > > If you deal with data objects and dictionaries yuo'll always have a flat > structure, right? If you don't care about properties descriptors (getters > and setters) you can always use a for/in > > ``` > function flatEnumerables(a) { > for (var c, k, i = 1; i < arguments.length; i++) { > for (k in (c = arguments[i])) a[k] = c[k]; > } > return a; > } > ``` > This would do what you are looking for (which is the first time I > personally read/hear about somebody wanting `Object.assign` to behave like > a for/in) > > Would that work? > > Best Regards > > > > On Fri, Feb 27, 2015 at 12:56 PM, Andri Möll <[email protected]> wrote: > >> You are talking about "flatting" all properties, which is an undesired >> overhead. >> >> >> Umm, Object.assign is as it is because of performance? I don’t think it >> is nor is that a good reason. Every property access in JavaScript takes >> inheritance into account and there are thousands more than a Object.assign >> call here and there. >> >> But what's bugging me every time more, is that somebody had a very bad >> idea to spread `Object.assign` as something good for inheritance or object >> cloning. >> >> Where does this come from? `Object.assign` retrieves properties and >> ignore getters and setters, is the last tool you want to use as >> substitution principle because it breaks. >> >> >> Ignores getters? You mean merely reads them? That’s not ignoring. Getters >> are an implementation detail of an interface. >> Prototypes aren't only useful for sharing behavior. They’re just as >> useful for *data objects and value types*. Nothing breaks when you clone >> or assign them around. >> >> Object.assign just read properties from one object and assign them to >> another. Something you used to do by hand. It’s just shorter to type >> assign(A, B) than type all properties of B out manually. If it’s _not_ >> meant to be the function-equivalent of `*for (var key in source) >> target[key] = source[key]*` then that’s too bad as my money is on it’s >> going to be used as such. I definitely want to use it for that. >> >> But what's bugging me every time more, is that somebody had a very bad >> idea to spread `Object.assign` as something good for inheritance or object >> cloning. >> >> Are you dealing with prototypes and `Object.assign` ? You gonna have way >> more problems than a missed flattered structure. >> Can you explain what is your goal ? Wouldn't this work? >> >> >> Inheritance? Inheritance is an implementation detail. A function >> receiving an object must not care about its inheritance tree as long as it >> fulfills the required interface. That’s what the LSP says as well. Even >> though JavaScript has no explicit concept of interfaces or types, they’re >> implicit in any function call. >> >> My goal is to save people from having to think every time they call a >> function whether this 3rd party function ignores inherited properties or >> not. If the callee uses Object.assign, it strips them out, if not, the >> dot-operator takes it into account. Surely no-one’s expecting everyone to >> prefix _every_ obj.name use with hasOwn: `*obj.hasOwnProperty(“name”) && >> obj.name <http://obj.name/>`*. Why do it in Object.assigns then is >> beyond me. Inconsistent and uncalled for. >> >> A. >> >> On Feb 27, 2015, at 14:24, Andrea Giammarchi <[email protected]> >> wrote: >> >> You are talking about "flatting" all properties, which is an undesired >> overhead. >> >> ```js >> >> var b = Object.create( >> Object.getPrototypeOf(a) >> ); >> >> Object.assign(b, a); >> >> ``` >> >> But what's bugging me every time more, is that somebody had a very bad >> idea to spread `Object.assign` as something good for inheritance or object >> cloning. >> >> Where does this come from? `Object.assign` retrieves properties and >> ignore getters and setters, is the last tool you want to use as >> substitution principle because it breaks. >> >> `Object.assign` is good only to define enumerable, writable, and >> configurable properties, like configuration or setup objects. >> >> Are you dealing with prototypes and `Object.assign` ? You gonna have way >> more problems than a missed flattered structure. >> >> Can you explain what is your goal ? Wouldn't this work? >> >> ```js >> >> var a = {}; // or anything else >> >> var b = Object.create( >> Object.getPrototypeOf(a) >> ); >> >> Object.getOwnPropertyNames(a).forEach(function (k) { >> Object.defineProperty(b, k, Object.getOwnPropertyDescriptor(a, k)); >> }); >> >> ``` >> >> >> Best Regards >> >> >> >> On Fri, Feb 27, 2015 at 11:52 AM, Andri Möll <[email protected]> wrote: >> >>> Hello, >>> >>> Why does Object.assign ignore inherited enumerable properties? >>> What is the problem to which ignoring inherited properties is the >>> solution to? >>> >>> All I can see is that it prevents a useful use of inheritance. The Liskov >>> substitution principle >>> <https://en.wikipedia.org/wiki/Liskov_substitution_principle> was >>> mentioned 27 years ago in ’87. Why is Object.assign breaking it? >>> >>> - Everyone who’s messing with Object.prototype has to do it an >>> non-enumerable style anyway. >>> - Most uses of Object.assign will likely be for objects with a finite >>> number of keys. Those form specific and implicit types from which people >>> are likely to read with the dot-operator. That takes inheritance into >>> account anyway. >>> >>> I don’t get the agenda to mess with object inheritance. If one wants >>> methods to only be in the parent and data on the child (so Object.assign >>> would only copy data), use a classical language. In a delegation-prototypal >>> language one should be able to inherit freely because of LSP >>> <https://en.wikipedia.org/wiki/Liskov_substitution_principle>. >>> >>> Andri >>> >>> _______________________________________________ >>> es-discuss mailing list >>> [email protected] >>> https://mail.mozilla.org/listinfo/es-discuss >>> >>> >> >> > >
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