On Feb 24, 2014, at 4:18 PM, Claude Pache wrote:

> 
> Personally, I consider that the impossibility to "yield a hole" must be considered as a feature, not a bug. Holes are useful in order to have consistent results for `Array.from([1, , 3])` (i.e., getting an exact copy), but their use should not be encouraged. (Note that, if you really want to, you can always (painfully) wrap a generator producing sentinel values with a hand-made iterable that forwards the results, transforming sentinel values into holes in the process.)

It easy enough to write an keys or entries iterator that ignores holes:

function *sparseKeys(array) {
   for (indx of array.keys()) if (Object.hasOwnProperty(array, key)) yield indx;
}

function *sparseEntries(array) {
   for (entry of array.entries()) if (Object.hasOwnProperty(array, entry[0])) yield entry;
}

The same thing could be done for values but that seems less useful.

Allen

On Feb 24, 2014, at 4:18 PM, Claude Pache wrote:

> Personally, I consider that the impossibility to "yield a hole" must be considered as a feature, not a bug. Holes are useful in order to have consistent results for `Array.from([1, , 3])` (i.e., getting an exact copy), but their use should not be encouraged. (Note that, if you really want to, you can always (painfully) wrap a generator producing sentinel values with a hand-made iterable that forwards the results, transforming sentinel values into holes in the process.)

It easy enough to write an keys or entries iterator that ignores holes:

```js
function *sparseKeys(array) {
   for (indx of array.keys()) if (Object.hasOwnProperty(array, key)) yield indx;
}

function *sparseEntries(array) {
   for (entry of array.entries()) if (Object.hasOwnProperty(array, entry[0])) yield entry;
}
```

The same thing could be done for values but that seems less useful.