in that way you are avoiding benefits provided by WeakMap + objects from
other realms are not instanceof Object + Object.create(null) instanceof
Object is false.
You probably want to use the WeakMap with anything that is typeof "object"
or typeof "function" and for everything else you can use the value itself
as unique identity for itself.
```js
const identities = new WeakMap();
let OBJECT_ID = 0;
function getObjectIdentity(obj) {
switch (typeof obj) {
case 'object':
case 'function':
let id = identities.get(obj);
if (!id) {
identities.set(obj, (id = ++OBJECT_ID));
}
return id;
default:
return obj;
}
}
```
Watch out collisions with possible integers or throw whenever the typeof is
number. You could use `this` only in "use strict" capable environment
otherwise primitives are going to be converted at runtime as objects with
every single time a different identity.
Regards
On Thu, Sep 10, 2015 at 8:02 PM, Michael McGlothlin <
mike.mcgloth...@gmail.com> wrote:
> One issue I did notice with WeakMaps is that because it can't use
> primative values as keys that they'll throw errors unless otherwise
> handled. Checking if they are an instanceof Object and if not using a Map
> instead seems to work.
>
> I wouldn't think using primatives as WeakMap keys would be an issue.
>
>
> const identities = new WeakMap();
> const primatives = new Map();
> let OBJECT_ID = 0;
>
> function getObjectIdentity() {
> if ( this instanceof Object ) {
> if ( !identities.has( this ) ) {
> identities.set( this, ++OBJECT_ID );
> }
> return identities.get( this );
> }
>
> if ( !primatives.has( this ) ) {
> primatives.set( this, ++OBJECT_ID );
> }
> return primatives.get( this );
> }
>
>
> On Wed, Sep 9, 2015 at 8:14 AM, Michael McGlothlin <
> mike.mcgloth...@gmail.com> wrote:
>
>> I think using WeakMaps is a good idea. Using a Symbol will keep from
>> cluttering the namespace with names others might want to use (id,label,etc)
>> and seems more consistent than some external means of accessing the id.
>> When I tried defining the value before I ran into issues with the prototype
>> chain which is why I was using get and a second 'hidden' property. Using
>> WeakMap seems like it'd fix the issue.
>>
>> Can't say I've used Object.assign much - will have to experiment with it.
>>
>> Thanks,
>> Michael McGlothlin
>> Sent from my iPhone
>>
>> On Sep 9, 2015, at 7:34 AM, Andrea Giammarchi <
>> andrea.giammar...@gmail.com> wrote:
>>
>> Well, to start with, you don't hide symbols, these are all exposed
>> through `Object.getOwnPropertySymbols` or Reflect.ownKeys so for your use
>> case looks like using just a non enumerable property would do as well.
>> And btw, even if Symbols don't show up in for/in and Object.keys, these
>> are by default also enumerable so Object.assign will copy them around
>> (reason I've used defineProperty with the value instead of just setting the
>> symbol, so it's non enumerable by default).
>>
>> As summary: do you want to be sure that object has a unique "lable" or
>> "id" associated with it? Use WeakMaps, otherwise be prepared to possible
>> clones around if some library uses Object.assign thinking that's a good way
>> to copy properties around.
>>
>> I still suggest the Labeler approach that Mark previously indicated.
>>
>> Regards
>>
>>
>>
>>
>> On Wed, Sep 9, 2015 at 1:15 PM, Michael McGlothlin <
>> mike.mcgloth...@gmail.com> wrote:
>>
>>> Using frozen objects and such seems a lot more complex to me than just
>>> using a property. Using a symbol to hide the property from cluttering seems
>>> to go along with how other things are being done. And it's my understanding
>>> that other than hiding it that using a Symbol for a name is nothing special
>>> - does it have some negative factor that should make using it less
>>> attractive?
>>>
>>> 📱 Michael McGlothlin
>>>
>>> On Sep 9, 2015, at 5:36 AM, Andrea Giammarchi <
>>> andrea.giammar...@gmail.com> wrote:
>>>
>>> That's similar to the Labeler proposed by Mark, except it needs to
>>> search for the thing twice (wm.has + wm.get instead of just wm.get which
>>> would be just fine as check if you count from 1 instead of 0 ;-) )
>>>
>>> Although I need to understand if you have a wm why wouldn't you just use
>>> that instead of a Symbol ... so the Labeler seems again a more appropriate
>>> pattern for this problem.
>>>
>>> Just my thoughts
>>>
>>> On Wed, Sep 9, 2015 at 10:51 AM, Michał Wadas <michalwa...@gmail.com>
>>> wrote:
>>>
>>>> Following solution will work:
>>>>
>>>> (function(){
>>>> const wm = new WeakMap();
>>>> Symbol.identity = Symbol( 'Symbol.identity' );
>>>> let i = 0;
>>>> Object.defineProperty(
>>>> Object.prototype,
>>>> Symbol.identity,
>>>> {
>>>> get: function () {
>>>> if (wm.has(this)) return wm.get(this);
>>>> wm.set(this, Symbol(i++));
>>>> return wm.get(this);
>>>> }
>>>> }
>>>> );
>>>> })()
>>>>
>>>>
>>>> 2015-09-08 23:29 GMT+02:00 Andrea Giammarchi <
>>>> andrea.giammar...@gmail.com>:
>>>>
>>>>> as side note, that's just a lazy assignment that doesn't need two
>>>>> symbols and a constant get invoke ...
>>>>>
>>>>> ```js
>>>>> Symbol.identity = Symbol( 'Symbol.identity' );
>>>>> var OBJECT_ID = 0;
>>>>> Object.defineProperty(
>>>>> Object.prototype,
>>>>> Symbol.identity,
>>>>> {
>>>>> get: function () {
>>>>> // first time this is invoked ... and no more ...
>>>>> Object.defineProperty(this, Symbol.identity, {value:
>>>>> ++OBJECT_ID});
>>>>> // from now own, direct property access \m/
>>>>> return this[Symbol.identity];
>>>>> }
>>>>> }
>>>>> );
>>>>> ```
>>>>>
>>>>> Regards
>>>>>
>>>>> On Tue, Sep 8, 2015 at 9:57 PM, Michael McGlothlin <
>>>>> mike.mcgloth...@gmail.com> wrote:
>>>>>
>>>>>> I try to keep it pretty simple. It's not fancy but the times you want
>>>>>> fast and dirty information like this are the same times you don't want to
>>>>>> have to define it manually.
>>>>>>
>>>>>> Symbol.identity = Symbol( 'Symbol.identity' );
>>>>>> const identity = Symbol( 'identity' );
>>>>>> var OBJECT_ID = 0;
>>>>>> Object.defineProperty( Object.prototype, Symbol.identity, {
>>>>>> get: () => {
>>>>>> if ( !Object.hasOwnProperty.call( this, identity ) ) {
>>>>>> this[ identity ] = ++OBJECT_ID;
>>>>>> }
>>>>>> return this[ identity ];
>>>>>> }
>>>>>> } );
>>>>>>
>>>>>> On Tue, Sep 8, 2015 at 1:44 PM, Mark S. Miller <erig...@google.com>
>>>>>> wrote:
>>>>>>
>>>>>>> See Labeler at
>>>>>>>
>>>>>>> http://wiki.ecmascript.org/doku.php?id=harmony:weak_maps#unique_labeler
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On Tue, Sep 8, 2015 at 11:16 AM, joe <joe...@gmail.com> wrote:
>>>>>>>
>>>>>>>> Didn't send to list, something is wrong with my reply all. Sorry
>>>>>>>> about that. Stupid mobile gmail.
>>>>>>>> ---------- Forwarded message ----------
>>>>>>>> From: "joe" <joe...@gmail.com>
>>>>>>>> Date: Sep 8, 2015 11:15 AM
>>>>>>>> Subject: Re: Object id, hash, etc?
>>>>>>>> To: "Garrett Smith" <dhtmlkitc...@gmail.com>
>>>>>>>> Cc:
>>>>>>>>
>>>>>>>> I agree with this request. This is the logical complement to
>>>>>>>> valueof, I think. And yes, for most ID use cases this isn't a good
>>>>>>>> fit, but
>>>>>>>> we're not talking about the general case, just the cases where a python
>>>>>>>> style id() function *is* appropriate.
>>>>>>>>
>>>>>>>> Joe
>>>>>>>> On Sep 8, 2015 9:08 AM, "Garrett Smith" <dhtmlkitc...@gmail.com>
>>>>>>>> wrote:
>>>>>>>>
>>>>>>>>> On 9/8/15, Michael McGlothlin <mike.mcgloth...@gmail.com> wrote:
>>>>>>>>> > Is there a reason not to provide an object id and hash value as
>>>>>>>>> other
>>>>>>>>> > languages often do? I find myself defining an identity symbol on
>>>>>>>>> objects
>>>>>>>>> > with a value from a simple global counter. It makes it easier to
>>>>>>>>> debug if I
>>>>>>>>> > can just look at a log and see what objects and functions were
>>>>>>>>> active.
>>>>>>>>> >
>>>>>>>>> > Likewise a hash value would simplify a lot of comparisons and
>>>>>>>>> make it easier
>>>>>>>>> > to debug.
>>>>>>>>> >
>>>>>>>>> > I especially find the ID useful when working with bound
>>>>>>>>> functions as they
>>>>>>>>> > can be difficult to tell apart. I like to change toString() to
>>>>>>>>> provide the
>>>>>>>>> > ID followed by the code (flattened to one line).
>>>>>>>>> >
>>>>>>>>> >
>>>>>>>>>
>>>>>>>>> NFE's are safe to use where IE8 support isn't needed*.
>>>>>>>>> (function aa(){}).name; // "aa"
>>>>>>>>>
>>>>>>>>> As for using Object IDs and Object Pooling, lexically-scoped values
>>>>>>>>> have benefits over global ID generators (as your counter). The
>>>>>>>>> values
>>>>>>>>> can be passed in as a parameter to the Factory (useful with Private
>>>>>>>>> Proxy). There other benefits to this pattern regarding memory
>>>>>>>>> management and application design. Contact me if you'd like to
>>>>>>>>> learn
>>>>>>>>> more.
>>>>>>>>>
>>>>>>>>> * https://kangax.github.io/nfe/
>>>>>>>>> --
>>>>>>>>> Garrett
>>>>>>>>> @xkit
>>>>>>>>> ChordCycles.wordpress.com
>>>>>>>>> garretts.github.io
>>>>>>>>> personx.tumblr.com
>>>>>>>>> _______________________________________________
>>>>>>>>> es-discuss mailing list
>>>>>>>>> es-discuss@mozilla.org
>>>>>>>>> https://mail.mozilla.org/listinfo/es-discuss
>>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> es-discuss mailing list
>>>>>>>> es-discuss@mozilla.org
>>>>>>>> https://mail.mozilla.org/listinfo/es-discuss
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> --
>>>>>>> Cheers,
>>>>>>> --MarkM
>>>>>>>
>>>>>>> _______________________________________________
>>>>>>> es-discuss mailing list
>>>>>>> es-discuss@mozilla.org
>>>>>>> https://mail.mozilla.org/listinfo/es-discuss
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> es-discuss mailing list
>>>>>> es-discuss@mozilla.org
>>>>>> https://mail.mozilla.org/listinfo/es-discuss
>>>>>>
>>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> es-discuss mailing list
>>>>> es-discuss@mozilla.org
>>>>> https://mail.mozilla.org/listinfo/es-discuss
>>>>>
>>>>>
>>>>
>>>
>>
>
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