This message seems to have disappeared from the archive and since I referred to it in http://wiki.ecmascript.org/doku.php?id=strawman:default_operator I wanted to make sure a record existed.
Rick ---------- Forwarded message ---------- From: Ryan Florence <[email protected]> Date: Tue, Jun 12, 2012 at 11:45 AM Subject: Re: ||= is much needed? To: Rick Waldron <[email protected]> Cc: David Bruant <[email protected]>, [email protected] 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 On Jun 12, 2012, at 9:06 AM, Rick Waldron wrote: ahah, I asked the same question very recently [1]. Answer by Brendan Eich > [2]. > 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? > > David > > [1] https://twitter.com/DavidBruant/status/210654806732324864 > [2] https://twitter.com/BrendanEich/status/210750515808706561 > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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