Kevin that "from somewhere else" has same problems cross-realm `instanceof` would have, you can't always trust that and if you want to map identities just do it instead of adding extra code ;-)
On Wed, Aug 10, 2016 at 5:24 PM, Kevin Reid <[email protected]> wrote: > [no quotes because I'm not replying to anyone in particular] > > An advantage that has not been mentioned yet, of having a canonical > function instance for particular behaviors, is that it allows for some > library-level optimization by being able to know what a function does > (which is otherwise opaque). For a simple example: > > SomeKindOfImmutableCollection.prototype.map = function (f) { > if (f === Function.IDENTITY) { > return this; > } > ...build a new collection with f applied to elements and return it... > }; > > Of course, it would be silly to write coll.map(Function.IDENTITY), but a > caller might be passing the function from somewhere else. > > (I only intend to point out this one benefit, not to claim it justifies > the feature entirely.) > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > >
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