The recent mention of the private names strawman [1] in the "Standardizing
__proto__" thread led me to re-read the proposal. After staring at it for far
too long, I had the "aha!" moment, but it left me with a question.
The "Conflict-Free Object Extension Using Private Names" section includes a
code example in which a function declares a private name `clone`, uses that
private name to define several extensions to built-ins, and then returns the
value of the private name so that it can be passed to another scope. The outer
scope uses that returned value to set the value of its own private name called
`clone`, and is then able to call [].clone, {}.clone, etc., and have them point
to the methods that were defined inside the function.
Here's my question: what happens if, sometime after that snippet of code, a
user writes code that declares a `clone` property? Something like:
var MyObj = {
clone: function() {
return new MyObj(this);
}
};
In other words: it appears that, in order to use the `clone` sugar given in the
example, a user must "taint" a given scope so that all further references to
"clone" (after . or before : at least) will refer to that private name. That's
likely not what the user intends. Once a private name is declared in a given
scope, can it ever be "reclaimed" as public later on?
Or, to use another example: let's say `MyObj` was defined in a different scope,
one in which `clone` was assumed to be a public name. Can I do this...
private clone = installCloneLibrary();
var twin = [{a:0}, {b:1}].clone();
var thing = MyObj.clone();
... and have it work the way I intend? In other words, once ES5 fails to find
something with the `clone` private name defined on `MyObj`, will it try to find
the property with the _public_ name of `clone` before it gives up? (If I'm
reading this right, it won't.)
I think it's great that we're trying to find ways to make built-in extension
safer without beating the dead horse of namespaces. But I fear that the
proposal, in its current form, would be too cumbersome for that purpose.
Cheers,
Andrew
[1] http://wiki.ecmascript.org/doku.php?id=strawman:private_names
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