Feature Request: Managed Objects - nodejs

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Message from discussion Feature Request: Managed Objects
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Subject: Re: [nodejs] Re: Feature Request: Managed Objects
From: Nick Husher <nhus...@gmail.com>
In-Reply-To: <922cbe6c-e951-4307-8a38-168e688de...@q18g2000vbm.googlegroups.com>
Date: Fri, 17 Dec 2010 15:00:49 -0500
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Message-Id: <20726C81-1691-4C16-A134-AED89E9EE...@gmail.com>
References: <b593565f-f3ae-4202-aaec-24a536a03...@l24g2000vby.googlegroups.com> <922cbe6c-e951-4307-8a38-168e688de...@q18g2000vbm.googlegroups.com>
To: nodejs@googlegroups.com

I believe ECMAScript5 object and property descriptors API is the desired =
way to do what you're after:

http://ejohn.org/blog/ecmascript-5-objects-and-properties/



As far as I know, v8 has reasonably good ES5 object and property =
support. Last time I checked, though, they had one bug that may or may =
not apply to you:

Let's say you have a native object (say a DOM element in a web browser) =
and it has a property on it with an internal setter. For example, =
"innerHTML."

As you may know, you can do myDomElement.innerHTML =3D someString, and =
it will update the innards of the element with the browser-evaluated =
string. Clearly there's magic happening here beyond just setting a =
property. The problem is that if you try to get a pointer that getter or =
setter method in v8, it will return undefined:

var d =3D Object.getOwnPropertyDescriptor(myDomElement, "innerHTML");

d.getter // undefined
d.setter // undefined

This makes it impossible to intercept native property assignments. If =
you wanted to toss an event any time content was assigned to innerHTML, =
you would be unable in v8.

Testing in firefox indicates that its JS engine *does* hand back a =
pointer to a native function. In that browser it's possible to shim =
property assignments.

Last I checked, bugs filed about this get flagged as "not a bug."


Nick
____________________

Nicholas Husher
nhus...@gmail.com
http://nickol.us

On 17 Dec 2010, at 1:37 PM, Shimon Doodkin wrote:

> http://ejohn.org/blog/javascript-getters-and-setters/
>=20
> On Dec 17, 5:39 pm, ollym <oliver.mor...@kohark.com> wrote:
>> Would it be possible to add something like this:
>> It would obviously need some C++ implementation, but would be useful
>> for clever OEM/datastore implementations.
>>=20
>> var ManagedObject =3D require('util').ManagedObject;
>>=20
>> var obj =3D new ManagedObject({
>>    get: function(key) { console.log('GET: ' + key); return true; }
>>    set: function(key, value) { console.log('SET: ' + key + '=3D' +
>> value }
>>=20
>> });
>>=20
>> obj.value; // returns true
>> // Output:
>> // GET: value
>>=20
>> obj.value =3D false;
>> // Output:
>> // SET: value=3Dfalse
>>=20
>> obj.value; // returns true (still)
>> // Output:
>> // GET: value
>=20
> --=20
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>=20
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