On Wed, Jul 10, 2013 at 12:52 PM, Domenic Denicola <[email protected]> wrote: > Woah, François, that seems pretty overcomplicated; why not replace everything > inside the constructor with `this.message = message`? It has the same effect > in the browsers I've seen. (Also don't forget > `SomeError.prototype.constructor = SomeError`.) > > Anyway, to Jonas's point: I think `DOMError` is actually pretty OK. One thing > I noticed is that the ES5 spec (and presumably ES6, although I haven't > checked) is careful to never throw simple `Error` objects, but instead > `TypeError`s or `RangeError`s or so on. I infer that they are leaving bare > `Error` for user cases. I think "the platform" should generally follow this > lead; that is, the DOM should leave bare `Error`s to the user, and throw > `DOMError`s or `TypeError`s or `RangeError`s for its own errors. > > To answer your more general question, authors are strongly discouraged from > ever throwing anything that is not `instanceof Error`, see e.g. Guillermo > Rauch's [A String is not an > Error](http://www.devthought.com/2011/12/22/a-string-is-not-an-error/). Also, > the `name` property is generally the same across all instances of a > particular error type, i.e. > > ```js > errInstance.name === errInstance.constructor.name === > errInstance.constructor.prototype.name === > Object.getPrototypeOf(errInstance).name > ``` > > (You can verify this for all the built-in ES5 errors.) Usually a `code` > property is used for more specific information, from what I've seen. But yes, > that has to be added manually with a bit of awkwardness, i.e. > > ```js > const e = new DOMError("The message"); > e.code = "TimeoutError"; > throw e; > ```
Note that (new DOMError) instanceof Error; returns false. So the DOM does do the "strongly discouraged" thing. Is this ok or bad? Also, the DOM does not create a new class for each different value of .name. I.e. you can get a DOMError whose .name is "NetworkError" or "AbortError". DOMError even has a constructor which allows setting .name to anything: new DOMError(name, message); In fact, there are no defined situations where the DOM creates DOMError objects whose .name is "DOMError". Again, is this ok or is it bad practice? / Jonas _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
