getify at gmail.com
Sat May 7 09:44:07 PDT 2011
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()`... or a call like
`Object.prototype.toString.call(window.opera) == "[object Opera]"` (a common
browser inference for Opera) is easily fake'able.
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