After some research iterators cannot be used because of lack of functions on them. However, for brevity and efficiency these sorts of functions should still exist.
Sebastian Original Message From: [email protected] Sent: August 4, 2017 3:10 PM To: [email protected] Subject: Re: Array findLast() and findLastIndex() I'm thinking that this may have performance benefits. The naïve approach would be something like: ```js function findLast(array, fn) { return array.reverse().find(fn); } ``` Note that this requires a reversed copy of `array` to reside in memory before `find` can be run, which is not a particularly useful thing to do when all you want is to start the search from another direction. Instead, you would have to do something like: ```js function findLast(array, predicate) { for (let i = array.length - 1; i >= 0; --i) { const x = array[i]; if (predicate(x)) { return x; } } } ``` which does the job, I guess. Apart from performance considerations, I would find it practical if all methods that work in *some* direction had a counterpart for the other direction, c.f. `trim{Start,End}`, `pad{Start,End}`, `reduce{,Right}`. It would be consistent, would it not? On Friday, August 4, 2017 8:35:52 PM CEST Sebastian Malton wrote: > I don't specifically have an exact use case but I can definitely think of > some use cases for them. However, if these sorts of functions also work for > array iterators then a reverse entries functions should suffice. > > Sebastian > > From: [email protected] > Sent: August 4, 2017 2:26 PM > To: [email protected] > Cc: [email protected] > Subject: Re: Array findLast() and findLastIndex() > > indexOf and reduce are the only iteration methods that have "reverse" > versions - I think to add any others, a clear case would have to be made > that *all* of them shouldn't get the same treatment. > > What's your use case? > > On Fri, Aug 4, 2017 at 11:19 AM, Sebastian Malton <[email protected]> > wrote: This function would be like find but would iterate from back to > front. We already have find/findIndex but unlike indexOf they don't have a > last counterpart. > > Sebastian > > > _______________________________________________ > 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 _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
