| 05:36 | <rkirsling> | wait I don't think I realized that it's legal to return random crap from a constructor |
| 05:37 | <rkirsling> | so class C { foo() { return 3; } constructor() { return [1]; } } is an uninstantiable class then?(in the sense that you can call new C() but you can never get "a C", so foo could only be accessed via C.prototype) |
| 05:37 | <rkirsling> | does that have a non-illegitimate usage? |
| 15:15 | <Aapo Alasuutari> | so |
| 15:16 | <rkirsling> | it is valid code, yes, otherwise I wouldn't be talking about it lol |
| 15:19 | <bakkot> | depends on what you mean by "illegitimate". i believe the functionality is there so you could match es5-style "classes" which did the same thing. also lets you wrap the return value in a Proxy or whatever |
| 15:20 | <bakkot> | these days the only real use I see for it is to stamp private fields on existing objects (class id { constructor(x){ return x } }; class stamp { #priv; constructor(o){ super(o) } }; new stamp(foo); // foo now has .#priv |
| 15:20 | <bakkot> | the "return override trick" |
| 15:20 | <bakkot> | but this is hateful and you shouldn't do it |
| 15:41 | <shu> | loathsome return override |
| 16:01 | <rkirsling> | yeah by legitimate I meant not hateful/loathsome 😅 thanks for confirming |
| 16:01 | <rkirsling> | (I learned this from Shu's Shared Structs deck) |
| 16:17 | <Michael Ficarra> | I think it was used for like "decorating" a constructor back in the day |
| 16:17 | <Michael Ficarra> | something like C = doParameterValidation(C); |
| 16:20 | <Michael Ficarra> | but while that is a use case for return override in functions, it is not a use case for return override in class constructors |
| 16:20 | <Michael Ficarra> | that feature probably should've been left on the ES2015 cutting room floor |
| 19:03 | <Bradford Smith> | A factory function is better, but I have seen the "return from constructor" feature used to allow new Foo(x) to always return the same object for a given x value. |
| 19:04 | <shu> | that's high-level hating |
| 19:04 | <shu> | why would you want new to not be actually new |