Yes the proposed syntax is a special case for arrays. tis 14 juli 2015 kl 12:23 skrev Edwin Reynoso <[email protected]>:
> Something wrong with server that doesn't let me edit. > > But what I meant by the first code snippet was: > > ```JS > for(let a, b of new Set([1,2])) // what would `a` and `b` be here? How > would it know what to extract?? > ``` > Would `b` just be `undefined`, yet for an array it returns the `index` how > does it determine that unless again this is special to Arrays?? because > `b/index` could be anything else, that's not obvious compare to > destructuring. > > > On Tue, Jul 14, 2015 at 12:13 AM, Edwin Reynoso <[email protected]> wrote: > >> So I'm assuming this would be special to arrays?? >> >> because destructuring works fine for anything that's iterable: >> >> meaning how would it know what to take out for Sets?? >> >> ```JS >> for(let value, index of [1,2]) { >> // do something >> } >> ``` >> >> With destructuring we at least know what's being extracted (not sure if >> destructured would be the right word, clueless on that): >> >> ```JS >> let it = [1,2].entries(); >> let [index, value] = it.next(); >> // same as: >> let [index, value] = [0, 1]; >> // the matching is obvious >> ``` >> >> With your suggestion it's not obvious: >> >> ```JS >> for(let value, index of [1,2]) // how does it know what value and index >> would be?? >> ``` >> >> I don't think this would be done if it's only for Arrays. >> >> On Tue, Jul 14, 2015 at 12:04 AM, Tingan Ho <[email protected]> wrote: >> >>> >Unfortunately we can't have both... >>> ``` >>> for (let [index, value] of values){ >>> ``` >>> >>> I was suggesting the syntax: >>> ``` >>> for (let value, index of values){ >>> ``` >>> `value` comes first and no `[ ... ]`. >>> >>> >>> >>> On Tue, Jul 14, 2015 at 11:52 AM, Logan Smyth <[email protected]> >>> wrote: >>> >>>> Unfortunately we can't have both >>>> >>>> ``` >>>> for (let value of values){ >>>> ``` >>>> >>>> and >>>> >>>> ``` >>>> for (let [index, value] of values){ >>>> ``` >>>> >>>> Over all, the first one is the more likely one on a day-to-day basis. >>>> >>>> The `[]` are needed because the `for...of` follows the standard rules >>>> for assignment, so it uses standard destructuring, and JS array >>>> destructuring requires `[]`. >>>> >>>> ``` >>>> for (let [index, value] of values.entries()){ >>>> ``` >>>> >>>> is essentially is the same as >>>> >>>> ``` >>>> for (let pair of values.entries()){ >>>> let [index, value] = pair; >>>> ``` >>>> >>>> As for your last question, `.entries` returns an iterator, so it will >>>> not create a copy of the array. >>>> >>>> On Mon, Jul 13, 2015 at 7:43 PM, Tingan Ho <[email protected]> wrote: >>>> >>>>> >for (let [index, value] of [1, 2, 3].entries()) >>>>> console.log(index + ": " + value) >>>>> >>>>> I still think most people will write: >>>>> >>>>> ``` >>>>> for (let value of values) { ... } >>>>> ``` >>>>> and then rewrite the whole expression inside the `for-loop` when they >>>>> find out that they need the index too: >>>>> ``` >>>>> for (let [index, value] of [1, 2, 3].entries()) >>>>> console.log(index + ": " + value) >>>>> ``` >>>>> `for (let value, index of values) { ... }` is still much easier to >>>>> type than `for (let [index, value] of [1, 2, 3].entries())` and also more >>>>> readable. >>>>> >>>>> >>>>> Also, doesn't that makes a copy of the `[1, 2, 3]`? >>>>> >>>>> -- >>>>> Sincerely, >>>>> >>>>> Tingan Ho >>>>> @tingan87 <https://twitter.com/tingan87> >>>>> >>>>> _______________________________________________ >>>>> es-discuss mailing list >>>>> [email protected] >>>>> https://mail.mozilla.org/listinfo/es-discuss >>>>> >>>>> >>>> >>> >>> >>> -- >>> Sincerely, >>> >>> Tingan Ho >>> @tingan87 <https://twitter.com/tingan87> >>> >>> _______________________________________________ >>> 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
