I am not sure I understood: is not throwing and a silent failure preferred?
'cause that method won't be there anyway...
I need to write chapter 3 of my quadrilogy of posts related to descriptors
and inheritance* but you can "simply" avoid that problem via
`Object.defineProperty(Pony.prototype, 'toString', {value: function () {}})`
This will most likely work everywhere except in old mobile browsers such
Palm Pre and Android 2.2 or 2.3, cannot remember, where this bug will show
up:
```javascript
var hasConfigurableBug = !!function(O,d){
try {
O.create(O[d]({},d,{get:function(){
O[d](this,d,{value:d})
}}))[d];
} catch(e) {
return true;
}
}(Object, 'defineProperty');
```
Accordingly, with these browsers the following code will fail:
```javascript
Object.defineProperty(Function.prototype, 'test', {
get: function () {
return Object.defineProperty(this, 'test', {
value: 'OK'
}).test;
}
});
```
but not this one:
```javascript
var proto = {};
Object.defineProperty(proto, 'test', {
get: function () {
if (hasConfigurableBug) {
var descriptor = Object
.getOwnPropertyDescriptor(proto, 'test');
delete proto.test;
}
Object.defineProperty(this, 'test', {
value: 'OK'
});
if (hasConfigurableBug) {
Object.defineProperty(proto, 'test', descriptor);
}
return this.test;
}
});
```
The key is keep properties configurable so that these can be deleted and
put back later on ... although this goes against that feeling of security
`Object.freeze(Object.prototype)` or `Object.freeze(global)` gives us ...
but I still believe that few edge cases a part these operations should be
avoided.
Anyway, please update this thread whenever a decision has been taken so I
can point to this one in one of these posts.
* [part 1](
http://webreflection.blogspot.com/2014/03/what-books-wont-tell-you-about-es5.html
)
[part 2](
http://webreflection.blogspot.com/2014/03/what-books-didnt-tell-you-about-es5.html
)
part 3 with solutions to this problem coming soon
On Wed, Mar 26, 2014 at 11:24 AM, Jason Orendorff <jason.orendo...@gmail.com
> wrote:
> "use strict";
> function Pony() {}
> Object.freeze(Object.prototype);
> Pony.prototype.toString = function () { return "Pony"; };
>
> The last line here throws a TypeError in ES5 and ES6.* Can we change
> it? To me, it stands to reason that you should be able to freeze
> Object.prototype and not break your other code, as long as that code
> doesn't actually try to modify Object.prototype.
>
> This bit some Mozilla hackers in <http://bugzil.la/980752>.
>
> Compatibility: Changing from throwing to not-throwing is usually ok.
> In addition, I don't think Chrome implements this TypeError. So
> presumably the web can't be depending on the exception.
>
> Patch: Step 5.a of [[Set]] could be changed like from:
> a. If ownDesc.[[Writable]] is false, return false.
> to:
> a. If ownDesc.[[Writable]] is false and O and Receiver are the
> same object, return false.
>
> -j
>
>
> *Why I think it throws:
>
>
> http://people.mozilla.org/~jorendorff/es6-draft.html#sec-ordinary-object-internal-methods-and-internal-slots-set-p-v-receiver
>
> Pony.prototype.[[Set]] reaches step 4.c. and tail-calls
> Object.prototype.[[Set]], which reaches step 5.a. and returns false.
>
> The TypeError is thrown from step 6.d. of PutValue:
> http://people.mozilla.org/~jorendorff/es6-draft.html#sec-putvalue
>
> which is called from step 1.f. from AssignmentExpression Evaluation:
>
> http://people.mozilla.org/~jorendorff/es6-draft.html#sec-assignment-operators-runtime-semantics-
> _______________________________________________
> es-discuss mailing list
> es-discuss@mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
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