On Thu, Dec 16, 2010 at 11:40 PM, Yu-Hsuan Lai <rainco...@gmail.com> wrote:
> I read "Good Parts", and it use Object#beget to implement prototypal
> inheritance.
Try using (ES5) `Object.create` instead, when available. And preferably not
the one that Doug recommends ;)
> beget = function (o) {
>
Undeclared assignment. That's something to avoid; Oh, and a ReferenceError
in ES5 strict mode.
> f = function () {};
>
Another undeclared assignment, leaking `f` to the global scope. Prepend
`var` (to make it a function expression) or change to `function f(){}`
(function declaration). Also consider taking `f` outside of "beget" for
performance reasons (idea originally introduced by Cornford few years ago):
var beget = (function() {
function F(){ };
return function(o) {
F.prototype = o;
return new F;
};
})();
(you can even give returning function a "name", turning it into a fancy NFE
(named function expression)):
var beget = (function() {
function F(){ };
return function beget(o) {
F.prototype = o;
return new F;
};
})();
> f.prototype = o;
> return new f();
> }
>
> a = {... object literal ...};
> b = Object.beget(a);
>
> It can build a prototype link when a object is created.
> But if I want to dynamically change the prototype link of a object?
>
"prototype link" that you're talking about — which I would rather refer to
as [[Prototype]], to stick to proper terminology — is not something that you
can change after object creation. Not in standard ES3 or ES5. You can do it
in a non-standard way. One of them is "__proto__" property, in
implementations which expose [[Prototype]] through it, and which allow
[[Prototype]] to be modified via __proto__ assignment.
[...]
--
kangax
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