Angus Croll wrote:
Yes the thread needs wrapping up. Maybe I can attempt summarize the dilemma - with a question: Is call/apply just a remedy for non-lexical this assignment? Or is it a powerful feature in it own right. I'm with the second camp, but I think I'm in the minority in this list
The second, of course :-) Herby
On Tue, Jun 5, 2012 at 10:23 AM, Brendan Eich <[email protected] <mailto:[email protected]>> wrote: Russell Leggett wrote: On Tue, Jun 5, 2012 at 12:36 PM, Brendan Eich <[email protected] <mailto:[email protected]> <mailto:[email protected] <mailto:[email protected]>>> wrote: What I perceive from the JSFixed effort, and from Angus who is good enough to post here: people have a particular concern that fat-arrow is too sweet and it will lure the children into the witch's house: passing fat arrows to dynamic-this APIs. We have data suggesting that fat arrows address the dominant use-case, thanks to Kevin Smith and others. So fat arrows are in ES6, well and good. I think the particular concern about => being an attractive nuisance for some APIs such as Angus's mixin combinators, which rely on .call overriding |this|, can be addressed by adding -> too. Angus agrees, but -> is not on the boards for ES6 (yet). We could try to revive ->, but first, we should face the attractive nuisance argument squarely, instead of dancing around it with isBound abuses that try to "catch fat arrow going into the witch's house". I think that with ->, a similar problem will still crop up - specifically that => will be the more common use, and then in the rare case that -> is needed, people may still use =>. I agree. The problem we'll then see is anxiety over "which arrow?" -- the Paradox of Choice (Schwartz). Do we still need isBound to catch that error as well? Even with the choice of -> or =>, the person writing the code has to know which one to use and why. That means they have to understand the whole dynamic |this| problem. Agreed, so (while we are spiraling, no worries) this helps. We cannot remove the dynamic vs. bound |this| choice from JS. But we can avoid adding choice when shortening, based on use-case frequency analysis. This, we have done (many thanks to Kevin Smith again), and it is why => got into ES6. I think that the dynamic |this| behavior of jQuery is not something that should be encouraged. I understand it is probably mostly that way because of the dom event api, JQuery goes further, I think simply due to mimesis. The DOM binds |this| to the event target but in the context of the old DOM level 0, where the only way to attach an event handler was as a method of the target, this was not "wrong". JQuery goes much, much further down the path to crazy |this| dynamic binding. but that doesn't change the fact that it really has a bad smell to it. On this everyone agrees. No disrespect to JQuery, but it is important to know what *not* to imitate. We know now, so we shouldn't be using JQuery as a rationale for dynamic-this short forms or isBound as a general tool. CoffeeScript has ->, but if you look at the examples, none of them actually make use of dynamic |this| except for methods, and we're adding a nice method syntax, so it isn't really needed. Method syntax, and => should cover the majority of cases and lead people down the right path. This is the current ES6 state and rationale, indeed. I know this is going around in a circle, but my point is that adding -> doesn't fix the problem, which is devs not knowing when to use => and when to use function. It's a good point. I hope we can wrap this thread up. It has been helpful to disclose or emphasize the situation: 1. "soft-bind" breaks abstractions and won't fly with implementors. 2. isBound needs more discussion but it too breaks abstractions and it must be defined (Mark's definition) to work for all this-insensitive functions. 3. => covers the dominant use-case for functions not using |this| and functions capturing lexical |this| via .bind or var self=this. 4. Adding -> doesn't avoid confusion over whether to use => or function, it only adds a shorthand -- good for those who want this -- and at the same time (the paradox of choice) creates anxiety over "which arrow do I use?". We could add isBound. We could add -> too. Right now ES6 has => only, based on a weighting of the costs and benefits in 1-4. /be _________________________________________________ es-discuss mailing list [email protected] <mailto:[email protected]> https://mail.mozilla.org/__listinfo/es-discuss <https://mail.mozilla.org/listinfo/es-discuss>
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