Anyway, if anyone is interested, I've published the `assign-properties` module [1]
[1] https://github.com/WebReflection/assign-properties#readme On Thu, Feb 13, 2020 at 7:51 PM Andrea Giammarchi < andrea.giammar...@gmail.com> wrote: > The fact `assign` doesn't copy descriptors and has potential side-effects > is documented extensively though, meaning there is room for improvement, or > simply a missing native way to do that, like it was for > `getOwnPropertyDescriptors`, that following your logic should've never > landed. > > But I guess I'd go with the usual "yet another micro library" approach > instead, so that at least I won't have to deal with assign shenanigans when > I mean to copy accessors too. > > On Thu, Feb 13, 2020 at 7:33 PM Jordan Harband <ljh...@gmail.com> wrote: > >> It seems like it’s the exact implementation you want, just for 1 object >> instead of N. >> >> Object.assign was added because versions of it were all over the web, >> used very frequently. How frequent is the pattern where people want to copy >> descriptors, such that it would deserve reification in the language? >> >> On Thu, Feb 13, 2020 at 10:23 AM Andrea Giammarchi < >> andrea.giammar...@gmail.com> wrote: >> >>> That has nothing to do with this, right? >>> >>> ```js >>> const {assign, defineProperties, getOwnPropertyDescriptors} = Object; >>> const assignProperties = (base, ...mixins) => defineProperties( >>> base, >>> mixins.reduce( >>> (descriptors, mixin) => assign( >>> descriptors, >>> getOwnPropertyDescriptors(mixin) >>> ), >>> {} >>> ) >>> ); >>> ``` >>> >>> On Thu, Feb 13, 2020 at 6:51 PM Jordan Harband <ljh...@gmail.com> wrote: >>> >>>> `Object.defineProperties(target, >>>> Object.getOwnPropertyDescriptors(source))`? >>>> >>>> On Thu, Feb 13, 2020 at 2:24 AM Andrea Giammarchi < >>>> andrea.giammar...@gmail.com> wrote: >>>> >>>>> Both `Object.assign` and `{...extend}` suffer a tiny gotcha: >>>>> properties are never assigned, neither retrieved, as accessors, with >>>>> side-effects too. >>>>> >>>>> Example: >>>>> ```js >>>>> const Counter = { >>>>> _count: 0, >>>>> get count() { >>>>> return this._count++; >>>>> } >>>>> }; >>>>> >>>>> const incr1 = Object.assign({}, Counter); >>>>> const incr2 = {...Counter}; >>>>> >>>>> console.log( >>>>> incr1.count, // 0 >>>>> incr2.count, // 1 >>>>> Counter._count // 2 >>>>> ); >>>>> >>>>> // functionality also compromised >>>>> console.log(incr1.count === incr1.count); >>>>> ``` >>>>> >>>>> Not only most of the time this is unexpected, but there's literally no >>>>> way to pass along accessors with a similar `Object.assign` ease, even if >>>>> that's what most developers would expect (at least up to the first time >>>>> they encounter above issue). >>>>> >>>>> How about we introduce `Object.assignProperties` instead? >>>>> >>>>> A polyfill example: >>>>> >>>>> ```js >>>>> const {assign, defineProperties, getOwnPropertyDescriptors} = Object; >>>>> const assignProperties = (base, ...mixins) => defineProperties( >>>>> base, >>>>> mixins.reduce( >>>>> (descriptors, mixin) => assign( >>>>> descriptors, >>>>> getOwnPropertyDescriptors(mixin) >>>>> ), >>>>> {} >>>>> ) >>>>> ); >>>>> ``` >>>>> >>>>> We can now use objects and mixins without side-effecting sources used >>>>> to extend, and preserving accessors in the process. >>>>> >>>>> ```js >>>>> const Counter = { >>>>> _count: 0, >>>>> get count() { >>>>> return this._count++; >>>>> } >>>>> }; >>>>> >>>>> const incr1 = Object.assignProperties({}, Counter); >>>>> const incr2 = Object.assignProperties({}, Counter); >>>>> >>>>> console.log( >>>>> incr1.count, // 0 >>>>> incr2.count, // 0 >>>>> Counter._count // 0 >>>>> ); >>>>> >>>>> // always false: preserved functionality >>>>> console.log(incr1.count === incr1.count); >>>>> ``` >>>>> >>>>> Thoughts ? >>>>> _______________________________________________ >>>>> es-discuss mailing list >>>>> es-discuss@mozilla.org >>>>> https://mail.mozilla.org/listinfo/es-discuss >>>>> >>>>
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