+1 (to all sentiments in the message :) ________________________________ From: Nathan Wall<mailto:[email protected]> Sent: 12/3/2012 17:53 To: Andrea Giammarchi<mailto:[email protected]>; Rick Waldron<mailto:[email protected]> Cc: [email protected]<mailto:[email protected]> Subject: RE: (Map|Set|WeakMap)#set() returns `this` ?
I'm not a person of influence, but as a JS developer, I agree with Andrea on this. I think Map#set() should return the value. I would expect the same behavior as obj[key] = value. I find Andrea's use case (m.get(k) || m.set(k, v)) more compelling than the method chaining possibilities. Nathan ________________________________ Date: Mon, 3 Dec 2012 14:21:24 -0800 Subject: Re: (Map|Set|WeakMap)#set() returns `this` ? From: [email protected] To: [email protected] CC: [email protected] IMHO, a set(key, value) should return the value as it is when you address a value var o = m.get(k) || m.set(k, v); // o === v // equivalent of var o = m[k] || (m[k] = v); // o === v a set with a key that returns `this` is a non case so almost as useless as the void return is. Usefulness comes with use cases ... except this jQuery chainability thingy that works fine for jQuery structure ( an ArrayLike Collection ) who asked for map.set(k0, v0).set(k1, v1).set(k2, v2) ? Or even map.set(k0,v0).get(k1) ? what are use cases for this? I am honestly curious about them because I cannot think a single one ... specially with the Set s.add(k0).add(k1).add(k2) ... this code looks weird inlined like this ... Thanks for your patience On Mon, Dec 3, 2012 at 2:04 PM, Rick Waldron <[email protected]<mailto:[email protected]>> wrote: On Mon, Dec 3, 2012 at 4:28 PM, Andrea Giammarchi <[email protected]<mailto:[email protected]>> wrote: I wonder what was the use case that convinced TC39 to return `this` with these methods. Assuming you read the notes, I proposed the agenda item based on the best practice of ensuring meaningful returns, and in the case of mutation methods, |this| is a meaningful return. Accordingly, this will never work: var query = map.has('queried') ? map.get('queried') : map.set('queried', $('myquery')); Previously, map.set() had a useless void return... And it will be something like: var query = map.has('queried') ? map.get('queried') : map.set('queried', $('myquery')).get('queried'); which is ugly and I don't really understand where map.set(k0, v0).set(k1, v1).set(k2, v2) could be useful. Accessing the object post-mutation allows for more expressive use of the API. Rick Thanks for clarifications ( a use case would be already good ) br _______________________________________________ es-discuss mailing list [email protected]<mailto:[email protected]> https://mail.mozilla.org/listinfo/es-discuss _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
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