On Wed, May 14, 2014 at 5:37 AM, Till Schneidereit < [email protected]> wrote:
> On Wed, May 14, 2014 at 8:48 AM, Mathias Bynens <[email protected]>wrote: > >> Previous discussion on this topic: >> http://esdiscuss.org/topic/array-prototype-last >> >> We should look at how existing utility libraries handle this behavior and >> base any proposals on that IMHO. Underscore and Lo-Dash have [`_.first`]( >> http://lodash.com/docs#first) and [`_.last`](http://lodash.com/docs#last), >> which both take an optional `callback` parameter, in which case all the >> first/last `n` elements for which `callback` returns a truthy value are >> returned. This seems like a sensible thing to add to the proposal. >> > > While I think having .last would be nice, I don't think it's worth the > considerable backwards-compatibility issues. We had to temporarily back out > Array#values from SpiderMonkey until we implement @@unscopable > semantics[1], because we ran into serious real-world breakage. I'm pretty > sure that "last" would break a lot more code, as it's even easier to think > up scenarios where that'd be used as a property name on an array used in > application logic. > > At the very least, I think having Array#last be a getter is entirely > untenable: a method would at least just be overwritten in most cases, > whereas a read-only accessor would just (silently, in non-strict code) > fail. A read-write accessor would probably be even worse: it'd silently (in > all code) do something entirely different than it did before. > > I do, however, like Axel's proposal[2] of adding .get() and .set() to > Array.prototype, and think that that'd be way less of a compatibility issue. > > > [1]: > https://mail.mozilla.org/pipermail/es-discuss/2013-July/thread.html#32185 > [2]: http://esdiscuss.org/topic/array-prototype-last#content-5 > I forgot about this, thanks for posting. I like get() much better as it can be a "first" or a "last" (or any in between) with less surface impact. Rick
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