See https://github.com/tc39/proposal-iterator-helpers
On Sat, Jul 27, 2019 at 1:45 PM Artem Kobzar <a.kobzar....@gmail.com> wrote: > The proposal based on really worst thing in JavaScript Arrays. > > If i as developer want to make declarative code with combination of > `Array#map`, `Array#filter` or `Array#reduce` - i will take a lot of > iterations (count of chain element will determinate count of iterations). > > ```js > const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]; > > const newArr = arr > .map(a => a + 1) > .filter(a => a % 2 === 0) > .filter((a, i) => i < 3); // [2, 4, 6], but 3 iterations across `arr` > ``` > > So, my proposal is: add lazy iterator with additional functions which help > to use declarative collection method in chain as "zero-abstraction" and > will iterate only once (will not be related to count of chain methods). > > Actually, i've already created implementation and usage of this > implementation looks like this: > > ```js > const arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]; > > const newArr = arr > .lazy() > .map(a => a + 1) > .filter(a => a % 2 === 0) > .take(3) > .collect(); // [ 2, 4, 6 ], but 1 iterations across `arr` > ``` > > And, actually, current implementation could be used with all `Iterable` > objects, if this object will implement method `fromIterator` (it's needed > for `LazyIterator#collect` method). > _______________________________________________ > es-discuss mailing list > es-discuss@mozilla.org > https://mail.mozilla.org/listinfo/es-discuss >
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