domenic at domenicdenicola.com (2013-11-15T18:54:03.843Z)
On Sun, Nov 10, 2013 at 11:33 PM, Corey Frang <gnarf37 at gmail.com> wrote: > Just to provide another way of working around it: That is excellent! Has all the upsides of the best of the other proposals and none of the downsides.
That is excellent! Has all the upsides of the best of the other proposals and none of the downsides. On Sun, Nov 10, 2013 at 11:33 PM, Corey Frang <gnarf37 at gmail.com> wrote: > Just to provide another way of working around it: > > var empty = {}; // or even a symbol? > > function splice(start = empty, count = 0, ...items) { > if (start === empty) { ... > } > > > On Mon, Nov 11, 2013 at 1:22 AM, Jonas Sicking <jonas at sicking.cc> wrote: > >> On Mon, Nov 11, 2013 at 2:12 AM, Allen Wirfs-Brock >> <allen at wirfs-brock.com> wrote: >> > One of the the few remaining uses of a function's 'arguments' binding >> is to >> > determine the actual number of passed arguments. This is necessary in >> some >> > overloading scenarios where a function has different behavior when an >> > argument is completely absent then it has when undefined (or any other >> > default value) is explicitly passed in that parameter position. That >> > situation occurs in a number of DOM APIs and even a few ES library >> > functions. >> >> I think the number is very low. I think I've heard of a total of four >> DOM functions which currently treat "not passed" as different from >> "explicitly passed undefined". And we're working on changing those so >> that the two are treated the same. Unclear if we'll be able to change >> all of them. >> >> So from the DOM point of view, I don't see a lot of reason to add >> convenience capabilities for detecting that difference. >> >> And in none of the cases in the DOM, does function.length become a >> problem. This is because in all of the cases the argument truly is >> optional, which means that .length does not include it. So for example >> for XMLHttpRequest.open you could write a JS implementation that looks >> like: >> >> function open(verb, url, ...args) { >> let [async, username, passwd] = args; >> if (args.length == 0) { >> async = true; >> } >> ... more code here ... >> } >> >> It is surprising to me that that is not the case in the ECMAScript >> APIs, but seems like that is history. >> >> / Jonas >> _______________________________________________ >> es-discuss mailing list >> es-discuss at mozilla.org >> https://mail.mozilla.org/listinfo/es-discuss >> > > > _______________________________________________ > es-discuss mailing list > es-discuss at mozilla.org > https://mail.mozilla.org/listinfo/es-discuss > > -- Cheers, --MarkM -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20131111/ea34173e/attachment.html>