love the token/Halt idea +1 easy to polyfill too However, and this is for David, some and every are *not* the opposite. With some, you return true only when you want to exit, with every you have to return true or false accordingly.
So, the return true in Array#some() is the equivalent of a break, while no return false is necessary. This is not the case of every, where the first time you don't return true, you are out. You know that but I just wonder how come you think these methods are confusing, I think these are OK. br On Tue, Mar 5, 2013 at 10:00 AM, Tab Atkins Jr. <[email protected]>wrote: > On Tue, Mar 5, 2013 at 9:38 AM, Kevin Gadd <[email protected]> wrote: > > Maybe I'm overlooking some past discussion on this, but if you want to > > be able to generally terminate iteration in constructs like > > Array.forEach (this seems like a pretty real world use-case), why not > > introduce an additional argument to the forEach/etc callbacks, for an > > 'iteration token'? > > > > I.e. if forEach currently passes 'item, index, array' to the callback, > > it can pass 'item, index, array, token'. token can be an object, such > > that: > > > > token.stopIteration(); // probably a better name for this > > > > terminates iteration. > > > > This has some upsides: > > You can mechanically detect a conforming implementation by looking for > > the token object via arguments[3] > > There's no risk of code written for a conforming implementation > > causing weird side effects (like an uncaught StopIteration) in a > > non-conforming iteration; it'll fail meaningfully > > The token is conceptually easy to understand and the implementation cost > is low > > Additional upside: we can canonically call the argument "halt", thus > finally completing Brendan's name in forEach's signature: > forEach(Element, Index, Collection, Halt). ^_^ > > ~TJ > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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