On Wed, Jun 11, 2014 at 1:37 PM, Domenic Denicola < [email protected]> wrote:
> It's also deceptive: it makes you think `Array.of` and `Array.from` are > functions, when in reality they are definitely methods. > Yes, you're right. What about Array subclasses? `from` and `of` are "inherited" when Array is subclassed, so these: 22.1.2.3 4 & 5 ( http://people.mozilla.org/~jorendorff/es6-draft.html#sec-array.of) 22.1.2.1 8.a & 8.b ( http://people.mozilla.org/~jorendorff/es6-draft.html#sec-array.from) 22.1.2.1 13 & 14 Which are are how `from` and `of` determine what to construct, will be replaced with a single step, being one of: Let A be the result of calling the [[Construct]] internal method of C with an empty argument list. Let A be the result of calling the [[Construct]] internal method of C with an argument list containing the single item len. But surely this step will also have to be guarded by IsCallable(this), which that means this: If IsConstructor(C) is true, then Let A be the result of calling the [[Construct]] internal method of C with an empty argument list. Else, Let A be ArrayCreate(0). Becomes: If IsCallable(C) is true, then Let A be the result of calling the [[Construct]] internal method of C with an empty argument list. Else, Let A be ArrayCreate(0). Or maybe that's not necessary? Is it preferable to just throw when someone writes any of these: let of = Array.of; of(1,2,3,4); let from = Array.from; from(arrayLikeOrIterable); let List = { of: Array.of }; List.of(1, 2, 3, 4); (Note that `Array.isArray` doesn't cease to work correctly when aliased) With the IsConstructor or IsCallable guard, these "just work"; without any guard, they'll throw TypeError exceptions: "object is not a function" or "undefined is not a function" (in strict mode). Neither of these errors are very obvious. Of course this can all be fixed with .bind() or a "bind" operator, but it just seems unfortunate to throw out something that's not harming the spec in favor something that might be problematic in end user code. Rick
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