Irakli Gozalishvili wrote:
Few questions on this new arrow functions:
let foo = x => x * x
1. What is foo.prototype ?
2. What does new foo(y) does ?
The idea with arrow function syntax (as opposed to block-lambda revival)
was to be as close to "just syntax" for functions. Obviously we've made
early-error restrictions but this design goal still stands. So the
answers are:
1. Same as for any user-defined function (a fresh Object instance).
2. Same as for any user-defined function.
And Object.getPrototypeOf(() => {}) === Function.prototype.
The restriction in ECMA-262 Ed. 5.1 11.4.3, "The typeof Operator",
penultimate row in Table 20:
Object (native or host and does implement [[Call]]) "function"
holds, so typeof () => {} === "function".
These are functions, arrow-functions to be precise (so with new syntax
and some syntactic restrictions).
3. Is there going to be equivalent of Function for arrow functions ?
No, see above.
4. Is Function.create(foo) going to work ?
Function.create is not specified and in Harmony yet, right?
5. Will foo.call, foo.apply pass in the `this` ?
Yes, see above.
/be
Regards
--
Irakli Gozalishvili
Web: http://www.jeditoolkit.com/
On Thursday, 2012-03-29 at 07:15 , Brendan Eich wrote:
This is all moot now -- see meeting notes and followups. Thin arrow is
not going to make it, we want one arrow. The |this| parameter for opting
into dynamic rather than default-lexical |this| also died. Method
definition shorthand covers the only strong use-case, as Kevin's
analysis shows.
/be
Herby Vojčík wrote:
Brendan Eich wrote:
Kevin Smith wrote:
I hate the CoffeeScript deviation, though. It's just confusing for
anyone who ever learned that fat-arrow binds |this| and thin-arrow
doesn't.
True. On the other hand, "all arrows bind |this|" is also quite simple
and easy to remember.
Yes, and I kept the part of the proposal that allows |this| as a
leading
arrow formal parameter, including with parameter default value. This
suggests a slight variation on the strawman, per your suggestion:
x -> { return this.x; } // lexical this for thin arrow
x => this.x // as for fat arrow
(this, x) -> { return this.x; } // dynamic this, five letter syn-tax
(this, x) => this.x // ditto for the expression-body form
I like this very much. Clear, orthogonal, readable.
It would be nice if this could get through.
/be
Herby
P.S.: Dynamic this no-arg function could also use one-arg shorthand?
this => this.x
this -> { return this.x; }
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