I apologize if the question I'm about to ask has already been "dealt
with", but I just ran across a nasty instance of it, and wanted to just
ping the topic to see what the language guardians have to say about it.
It's a well known fact that overwriting anything in Object.prototype (like
Object.prototype.toString, for instance) is a very bad idea, because it
breaks for-in looping. It also affects every single object, including even
natives/built-ins, often in unexpected ways.
So, a few questions:
1. Would it be possible to specify that changes to Object.prototype.* do
NOT affect any of the natives/built-ins?
2. Would it be possible for Object.prototype.* to be read-only for
ES-Harmony (or even just strict mode)?
3. By read-only, I mean that changes to it would just silently be
discarded. Alternatively (especially for strict mode), warnings/errors
could be thrown if attempting to override them?
I think that being able to override something like
Object.prototype.toString to "lie" about objects/values is a "security"
hole we should consider plugging. For instance, you can "lie" to
`document.location.href.toString()`
To clarify, you have to overwrite `String.prototype.toString` to "lie" in
this particular scenario. But the point is the same.
... or a call like `Object.prototype.toString.call(window.opera) ==
"[object Opera]"` (a common browser inference for Opera) is easily
fake'able.
--Kyle
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