Unless you have a specific requirement I am missing, your use case is more
elegantly resolved IMO using a custom generator that yields exactly the
information you need per iteration.
A functional approach using a function that has the information you need is
also another valid solution.
<div>-------- 元のメール --------</div><div>送信元： Tingan Ho <tinga...@gmail.com>
</div><div>日時:2015/07/14 PM1:32 (GMT+09:00) </div><div>宛先： Edwin Reynoso
<eor...@gmail.com> </div><div>Cc： es-discuss <es-discuss@mozilla.org>
</div><div>件名: Re: for statement with index and value </div><div>
</div>Yes the proposed syntax is a special case for arrays.
tis 14 juli 2015 kl 12:23 skrev Edwin Reynoso <eor...@gmail.com>:
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 <eor...@gmail.com> 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 <tinga...@gmail.com> 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 <loganfsm...@gmail.com> 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 <tinga...@gmail.com> 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
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--
Sincerely,
Tingan Ho
@tingan87
_______________________________________________
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