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
