I always forget to reply-all :) ---------- Forwarded message --------- From: Gus Caplan <[email protected]> Date: Fri, Jun 21, 2019, 16:34 Subject: Re: ECMAScript feature suggestion: Streaming Array items through filter/map/reduce functions To: Roma Bronstein <[email protected]>
I'm working on a proposal that adds generalized iteration methods (most of which are lazy). https://github.com/tc39/proposal-iterator-helpers I believe this would solve your problem. -Gus On Fri, Jun 21, 2019, 16:10 Roma Bronstein <[email protected]> wrote: > Thanks Oliver for the quick response. > > The problem for me with forEach, that it's pretty much like a for loop. > Anything can go inside the iteration logic. > However with filter/map/reduce/some/every functions, the intention is > explicit. > Also you don't need to implement basic array operations that the above > mentioned functions already provide. > > For instance in my opinion writing something like: > a.filter() > .map() > .reduce() > > Is much clearer and safer than: > > let reducedValue > a.forEach(item => { > if(!<filter condition>) return > const mappedItem = mappingLogic(item) > reducedValue = reduceLogic(mappedItem) > }) > > > > On Fri, Jun 21, 2019 at 11:58 PM Oliver Dunk <[email protected]> > wrote: > >> This seems like a good place to share the idea, and it’s helpful that you >> provided use cases etc. >> >> Is there a reason why you prefer the proposed syntax over the forEach >> loop you mentioned? Personally I like how the forEach is easy to >> understand, but maybe there are other examples of when the stream is useful >> and the polyfill is much more complex. >> >> > On 21 Jun 2019, at 16:32, Roma Bronstein <[email protected]> wrote: >> > >> > Hi, >> > >> > It's my first time suggesting a feature, hope I'm doing it correctly. >> > >> > I really like using Array.prototype.map(), Array.prototype.reduce() and >> all related functions. >> > The code is more readable and it looks better. >> > However, when I want to write performance sensitive code, chaining >> these functions is not a good approach. >> > For example, writing this: >> > // a is an Array of length N >> > const b = a.filter().map() >> > >> > will require 2 traversals over the whole array, up to 2*N iterations >> (if the filter passes all items). >> > >> > This is why I often resort to writing this: >> > const b= [] >> > a.forEach(() => { >> > if (/*the filter condition*/) >> > b.push(/*mapping logic*/) >> > }) >> > >> > Which requires only N iterations. >> > >> > I suggest adding a capability to streamline items to these functions. >> > I get my inspiration from Redis's transaction syntax where you declare >> starting a transaction and finally call EXEC in order to execute it. >> > So now I'll be able to write something like this: >> > const b = a.stream() >> > .filter() >> > .map() >> > .exec() >> > >> > Just to clarify the example: >> > I've declared that I'd like to stream array items of a. Then I've >> chained the functions I'd like to items to pass through. >> > Finally I've activated it using the exec() function. >> > >> > I'm not sure if this is the best syntactical approach, but this example >> is more intuitive to understand in my opinion. >> > >> > Another approach could be thinking about a "pipeline" operator like in >> UNIX cli, providing a more generic capability to pipeline iterators. >> > >> > Again, I hope I'm doing this correctly and in the right forum. >> > And if so, I'd be happy to hear some feedback. >> > >> > Thanks, >> > Roma >> > >> > >> > >> > _______________________________________________ >> > 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 >
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