Ok. I just updated the proposal.
Since T.J. felt so strongly about the use of the word "template", I removed
it from the proposal. No need to raise unnecessary ire.
Since using `new` to trigger the behavior is a no-go just like pragmas, I
introduced 2 new well known Symbols.
* `Symbol.SafeProto = Symbol("SafeProto")` to mark objects that should
exhibit the new behavior.
* `Symbol.UnsafeProto = Symbol("UnsafeProto")` to mark objects that **must
not** exhibit the new behavior.On Tue, Nov 27, 2018 at 1:13 PM Jordan Harband <[email protected]> wrote: > Correct, existing code *used with* existing code can't break. It's totally > fine for existing code that works with objects produced by new code to > break. > > On Tue, Nov 27, 2018 at 11:05 AM Ranando King <[email protected]> wrote: > >> Is this to say that no new feature is allowed to introduce breaking >> changes in existing code? >> >> On Tue, Nov 27, 2018 at 1:00 PM Jordan Harband <[email protected]> wrote: >> >>> What I meant by "preserve existing behavior" is that *all current code* >>> must retain the footgun. Any chance must only apply to new code that >>> explicitly opts in to it. >>> >>> On Tue, Nov 27, 2018 at 10:55 AM Ranando King <[email protected]> wrote: >>> >>>> > Not something you'd want to do often... >>>> >>>> Or ever. This is the foot-gun behavior. The same result can be achieved >>>> with a simple factory class. >>>> ```js >>>> class Example { >>>> //Don't use "this". It was flagged to use the updated prototype >>>> behavior. >>>> return Object.create(Example.prototype); >>>> } >>>> Example.prototype.sharedObject = { >>>> counter: 0 >>>> }; >>>> const e1 = new Example(); >>>> const e2 = new Example(); >>>> console.log(e2.sharedObject.counter); // 0 >>>> ++e1.sharedObject.counter; >>>> console.log(e2.sharedObject.counter); // 1 >>>> ``` >>>> This is what I meant when I said that the existing behavior isn't lost. >>>> There are still plenty of ways to achieve the foot-gun behavior if that is >>>> what's desired. What this proposal seeks is a means of making the most >>>> common path foot-gun free. >>>> >>>> Besides, a cleaner result can be achieved by using a static property. >>>> ```js >>>> class Example { >>>> } >>>> Example.counter = 0; >>>> >>>> const e1 = new Example(); >>>> const e2 = new Example(); >>>> console.log(e2.constructor.counter); // 0 >>>> ++e1.constructor.counter; >>>> console.log(e2.constructor.counter); // 1 >>>> ``` >>>> >>>> >>>> On Tue, Nov 27, 2018 at 10:30 AM T.J. Crowder < >>>> [email protected]> wrote: >>>> >>>>> On Tue, Nov 27, 2018 at 3:34 PM Ranando King >>>>> <[email protected]> wrote: >>>>> > The fact that the prototype is a 1st class, (usually) mutable >>>>> > object doesn't change the fact that it is a template. >>>>> >>>>> It fundamentally does, calling prototypes templates rather >>>>> short-changes them. Again, they're live objects: >>>>> >>>>> ```js >>>>> class Example { >>>>> } >>>>> const e = new Example(); >>>>> console.log(e.foo); // undefined >>>>> Example.prototype.foo = "bar"; >>>>> console.log(e.foo); // "bar" >>>>> ``` >>>>> >>>>> (http://jsfiddle.net/pot8cdq6/) A *template* wouldn't demonstrate >>>>> that sort of behavior. Perhaps it's just a semantic point, though. >>>>> >>>>> > As for changing `new` in an incompatible way, doesn't represent a >>>>> > significant or incompatible change in the behavior of `new`. >>>>> >>>>> Of course it does. If it didn't, it wouldn't solve the problem you >>>>> describe wanting to solve. Or was there some opt-in (other than the >>>>> pragma) >>>>> that I missed? The problem you describe is perfectly valid current code: >>>>> >>>>> ```js >>>>> class Example { >>>>> } >>>>> Example.prototype.sharedObject = { >>>>> counter: 0 >>>>> }; >>>>> const e1 = new Example(); >>>>> const e2 = new Example(); >>>>> console.log(e2.sharedObject.counter); // 0 >>>>> ++e1.sharedObject.counter; >>>>> console.log(e2.sharedObject.counter); // 1 >>>>> ``` >>>>> >>>>> (http://jsfiddle.net/m49jsxof/) Not something you'd want to do often, >>>>> but perfectly valid and I expect there are use cases for it, which >>>>> changing >>>>> it would break. >>>>> >>>>> Re the rest: Yes, it's complicated to solve for nested properties. But >>>>> again, you just repeat the pattern, and/or use a Proxy; you can certainly >>>>> preserve prototypes as needed. The way in which you do so will vary >>>>> dramatically depending on what your use case is and how much you want to >>>>> copy, etc. >>>>> >>>>> I certainly don't see adding new semantics to `new`. I could see a >>>>> library function setting things up for you, but I think the patterns would >>>>> be so project-specific that it's unlikely to go into the standard library. >>>>> >>>>> I'll step back at this point. >>>>> >>>>> Best, >>>>> >>>>> -- T.J. Crowder >>>>> >>>> _______________________________________________ >>>> es-discuss mailing list >>>> [email protected] >>>> https://mail.mozilla.org/listinfo/es-discuss >>>> >>>
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