+1 I desperately want this in the language.
AJ ONeal On Tue, Jun 12, 2012 at 11:14 AM, Rick Waldron <[email protected]>wrote: > > > On Tue, Jun 12, 2012 at 11:45 AM, Ryan Florence <[email protected]>wrote: > >> I use ||= very regularly in ruby and coffeescript, both of which have >> default arguments. >> >> I definitely agree that default arguments are a decent alternative. I >>> can't recall examples where it wouldn't be enough. Do you have use cases >>> where you would use ||= and default argument values couldn't be used? >>> >> >> Its super handy for caching and late/dynamic initialization of object >> properties. >> >> >> var events = { >> >> _callbacks: {}, >> >> on: function (topic, callback) { >> (this._callbacks[topic] ||= []).push(callback); >> ... >> }, >> ... >> }; >> >> >> It's also useful for settings object defaults, especially for expensive >> settings that you don't want to calculate in some `defaults` object that is >> merged into the settings. >> >> function ajaxWithError (settings) { >> settings.method ||= 'POST'; >> >> settings.elementPosition ||= this._getElementPositions(); >> >> settings.somethingWithInitialization ||= (function(){ >> var thing = new Thing(); >> thing.foo = settings.foo; >> return thing; >> })(); >> ... >> }; >> >> >> The ||= (function(){})() should remind any rubyist of `||= begin ... end` >> which is beloved by many. >> >> So yeah, I think its really useful outside of default arguments. >> >> - Ryan Florence >> >> > Forgive the dogpiling, but these are really excellent real-world use cases > that represent massive pain points in modern JavaScript programming. Thanks > for writing these up Ryan, I've added them to strawman: > http://wiki.ecmascript.org/doku.php?id=strawman:default_operator > > Rick > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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