So you should do the same with Promise methods but then you'll see overall a quite consistent performance drop when using all these subclasses.
We've been trying for about 10 years now ( http://dean.edwards.name/weblog/2006/11/hooray/ ) and yet we don't have a working and performing solution, which I guess is why somebody still pollutes global prototypes, everything becomes easier, including the ability to still use common literals to define objects or lists. Oh well :-) Best Regards On Fri, Apr 24, 2015 at 3:26 PM, Alex Kocharin <[email protected]> wrote: > > True, but it should be your responsibility (as a person who implements a > subclass) to resolve those issues. > > Thankfully, it's easily done: > > ``` > function MyArray(...args) { > var self = Array.apply(null, args) > Object.setPrototypeOf(self, MyArray.prototype) > return self > } > > Object.setPrototypeOf(MyArray.prototype, Array.prototype) > > ;[ 'slice', 'map', 'concat' /* whatever else */ ].forEach(function > (method) { > MyArray.prototype[method] = function (...args) { > var result = Array.prototype[method].apply(this, args) > Object.setPrototypeOf(result, MyArray.prototype) > return result > } > }) > > console.log(MyArray(1).slice(1) instanceof MyArray) > // true > ``` > > > 24.04.2015, 14:13, "Andrea Giammarchi" <[email protected]>: > > Not exactly ... if it's an Array, as example, the moment you > slice/map/splice/concat, etc will return an instanceof Array, not an > instance of whatever you have sublcassed. > > Regards > > On Fri, Apr 24, 2015 at 10:24 AM, Alex Kocharin <[email protected]> wrote: > > > I believe you can subclass anything using code like this: > > function MyPromise(executor) { > var self = new Promise(executor) > self.setPrototypeOf(self, MyPromise.prototype) > return self > } > Object.setPrototypeOf(MyPromise, Promise) > > > ... and it can be easily subclassed itself in the same way. > > > 24.04.2015, 04:02, "C. Scott Ananian" <[email protected]>: > > Is there any way to access `new.target` using ES5 syntax? > > It appears that the "correct" way to create a subclass using ES5 syntax is: > ``` > function MyPromise(executor) { > var self = Reflect.construct(Promise, [executor], new.target); > return self; > } > Object.setPrototypeOf(MyPromise, Promise); > ``` > But since `new.target` isn't accessible, we have to do something like: > ``` > function MyPromise(executor) { > var self = Reflect.construct(Promise, [executor], MyPromise); // <-- THIS > return self; > } > Object.setPrototypeOf(MyPromise, Promise); > ``` > which works for only a single level of subclassing. That is, it allows us > to create and instantiate MyPromise, but now nobody can subclass > MyPromise. That's too bad. > > Is there any way around this? > --scott > > ps. Use case: My `prfun` package on npm subclasses `Promise` in order to > add all the useful utility helpers without stomping on the global `Promise` > object. I'd like to do so in a way which is compatible with both native > ES6 promises (if they are available) and properly-written ES5 shims. > , > > _______________________________________________ > es-discuss mailing list > [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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