FWIW I do like prototypal inheritance ... but ... On Fri, Feb 27, 2015 at 8:45 PM, Andri Möll <[email protected]> wrote:
> That is not what people relying in Object.assign and ES6 will write, > because you cannot define properties in a generic class, only methods. > > > Classes are just syntactic sugar over prototypes after all. > except finally these behave like natives always have: non enumerable methods / accessors ... those that even you said don't want on your way > I’m definitely going to continue promoting use of plain old prototypical > approaches in addition to that because they're simple and elegant: > objects will still be used for composing and whenever you `Object.create(Object.getPrototypeOf(other))` you are still using prototypal inheritance. None of this has ever been solved in `Object.assign` though ... > why waste computation power in constructors when you can do so once on the > prototype. > 'cause 99% of the time you need to initialize your PERSON with a `name` property, as example ... do that in the object creation through an implicit initializer as constructor is: done! > I find that an advantage of prototypal languages over classical ones. > I guess you like `init` methods too then > > A bit of a plug in this regard, check out this simple observable > implementation that supports inheritance: > https://github.com/moll/js-concert > Boy does this save computation. No need to bind listeners for every object > (e.g. domain model) instance: > Model.prototype.on(“change”, onChange) is all you need. Beautiful, isn’t > it? ;-) > Check what DOM offered since about ever: EventListener interface: http://www.w3.org/TR/DOM-Level-2-Events/events.html#Events-EventListener You inherit this: ```js class EventListener { handleEvent(e) { var type = 'on' + e.type; if (type in this) this[type](e); } } ``` And BOOM, every class inheriting that will be able to create instances usable as handlers, no need bind listeners to anything anymore! ```js class DaClicker extends EventListener { constructor(el) { el.addEventListener('click', this); } onclick(e) { alert([e.type, this instanceof DaClicker]); } } var driver = new DaClicker(document); ``` How cool is that? Now, let's go back to `Object.assign` ... Well, that didn’t seem to prevent changing class method enumerability just > a little time ago. > and didn't affect `Object.assign` behavior ... we all agreed here enumerability had to be changed in order to be consistent with native classes and be able to extend them without causing unexpected behaviors ... it was the last window before breaking classes forever, while `Object.assign` is a method based on old ES3 concepts that has not much to do with ES6 and that was never meant to be used to extend objects. It's the wrong tool for the job, accessors are lost in the process, and everything else is ignored, including inheritance. > Sweet story you made out of the example. :-) Coming back to non-prose for > a sec, unless you get everyone to ignore Object.assign and use your > function, there’s no point in proposing your functions. That’s what I’ve > now repeated plenty of times. It’s going to hurt _us_ prototype-uses > because _others_ will use Object.assign where they need not. > There's no point in proposing `Object.assign` to deal with inheritance, prototypal inheritance, and de-facto extend ability. `Object.assing` has one well defined use case: copy own enumerable properties, that's it ... **really** ... that's just it. Good for setup or config options, nothing else! > Umm, that was already explained by Leon Arnott’s email: Object.assign is > cowpath pavement. Everyone seems to like a for-in assignment helper. Two of > most popular assign/extend implementation mentioned (jQuery, Underscore) > have supported inheritance for _at least_ 7 years. Do you not find that as > evidence “from the field"? > common extend do not loop over inherited properties, if these do is because these were written in an era where `Object.getPrototypeOf` and `Object.setPrototypeOf` where missing. You talked about computation power and you want to loop over everything per each `Object.assign` call ... I am sorry I don't follow you anymore here! > > Or am I preaching to the choir? Are you personally already in favor of > supporting inheritance in Object.assign? > `Object.assign` has **nothing to do with inheritance**, that's what I am saying, not just supporting. > Given what I’ve read from you so far you won’t be affected by it as it > seems to me you prefer to use this prototypal language in a classical way. > No, I do like prototypal inheritance and I love the fact it's still the root of JS inheritance. What is my personal position here is that `Object.assign` is the wrong method/tool/function to do anything prototypal or classical inheritance related. Developers should understand it, and I am realizing they don't ... like not at all! Best Regards > > A. > > On Feb 27, 2015, at 19:51, Andrea Giammarchi <[email protected]> > wrote: > > That is not what people relying in Object.assign and ES6 will write, > because you cannot define properties in a generic class, only methods. > > Moreover, back to your ES5/3compat example, if you have a person object, > you **never** inherit name, you always have your own name as you explicitly > set "John". > > You eventually inherit the surname, but that's indeed not your own so it > should not be copied as such, it should stay there inherited unless you > explicitly go to the inheritance office (the property descriptor officer) > and ask for an own surname. > > Same is for all people from Estonia, they all inherit their native country > when born, they have to hide it explicitly at the same "descriptor office" > in order to make them their own country. > > But all this goes down to why/how/where you need to retrieve these info. > That is the place you log through a for/in in order to reach all exposed > (read enumerables) properties. > That is where you log passing whatever it is through the function I've > written. > > Before? country isan accessible info, as the surname and other inherited > properties eventually would be, and only if re-set on top, will become own > properties. > > At the end of the day, `Object.assign` has been already adopted and > polyfilled and used for some time now, changing it now will probably break > all code based on it. > > Again, I think this is the first time I hear someone wanting a new method > being exactly like a for/in ... use for/in if that's what you need ( KISS ? > ) > > Best Regards > > > On Fri, Feb 27, 2015 at 5:27 PM, Andri Möll <[email protected]> wrote: > >> 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. >> >> >> Umm, that’s one tactic for sharing behavior. Yep. But I thought we agreed >> Object.assign is more useful for data/record objects than for objects with >> behavior. Ignoring inheritance because of methods is not an argument then. >> >> 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. >> >> >> Sadly not. Inheritance should not be conflicted with sharing behavior >> (methods). Entirely orthogonal concepts. It’s very useful to inherit from >> various data/record objects and pass those around. The receiver of such an >> object need never know there’s inheritance involved. >> >> [ 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 >> >> >> They thing to remember here is _other people’s code_. My code perfectly >> honors your inheritance chains when iterating or accessing properties. But >> me doing that doesn’t imply everyone else won’t use Object.assign to set up >> their defaults as is very convenient: `person = Object.assign({name: “”, >> age: 0}, person)`. You think they won’t? They already do so with >> Object.keys when it’s entirely unnecessary for 9/10 use-cases. >> >> 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. >> >> >> Nah, I’m saying inheritance is an implementation detail of my object. >> It’s none of the receiver’s/callee’s business how I implemented that >> particular interface (any agreed upon set of properties _is_ an interface). >> But the moment someone passes my object to Object.assign, they get the >> wrong output. Even if it should’ve been a no-op: `options = >> Object.assign({}, options)`. >> >> 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? >> >> >> I’ll leave JSON out of this discussion. Yeah, I’d like to set >> Object.prototype.toJSON, but I’m afraid there’s code somewhere that depends >> on it serializing only own properties. Ugh. >> >> 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` >> >> >> But it’s not me who wants to flatten stuff. It’s the people who will >> write functions or APIs that use Object.assign while setting their >> defaults. I don’t mind them flattening, but only if they don’t lose half of >> the properties to inheritance stripping while doing so. >> >> Am I explaining the problem wrong? I’m still surprised there are people >> who don’t find the following behavior retarded: >> >> ``` >> function logPerson(person) { console.log(“%s is from %s.”, person.name, >> person.country) } >> function logTraveler(person) { logPerson(Object.assign({name: >> “Traveller”}, person)) } >> >> var PERSON = {name: “Unnamed”, country: “Estonia"} >> var john = Object.create(PERSON) >> john.name = “John” >> >> logPerson(john) // => John is from Estonia. >> logTraveler(john) // => John is from undefined. >> ``` >> >> While a little contrived, like I said, Object.assign and its equivalents >> from libraries are already used to set defaults. >> Just in case: please don’t propose replacing every Object.create with >> Object.assign. >> >> A. >> >> On Feb 27, 2015, at 18:35, Andrea Giammarchi <[email protected]> >> wrote: >> >> 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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