Re: EcmaScript Proposal – Private methods and fields proposals.

[kai zhu]

as a javascript web-developer, can someone educate me on how private
class methods/fields would make one's life easier (rather than harder)
in getting web-projects shipped?

```
/*
 * how is this cited example better than using a plain object in a web-project?
 * can someone give actual common problems in
 * debugging/integrating/shipping web-projects,
 * that private methods/fields could help simplify (rather than complicate)?
 */
class HashTable {
  constructor() {
    private[Symbol.for('length')] = 0
  }
  set(key, value) {
    private[key] = value
  }
  get(key) {
    return private[key]
  }
}
```


On 4/17/18, Sultan <thysultan at gmail.com> wrote:
>>An instance has a fixed set of private fields which get created at object
> creation time.
>
> The implications of this alternative does not necessarily limit the
> creation of private fields to creation time, for example writing to a
> private field in the constructor or at any arbitrary time within the
> lifecycle of the instance.
>
> class HashTable {
>   constructor() {
>     private[Symbol.for('length')] = 0
>   }
>   set(key, value) {
>     private[key] = value
>   }
>   get(key) {
>     return private[key]
>   }
> }
>
>>How do you deal with inner nested classes wanting to refer to outer
> classes' private fields?
>
> Not sure i understood what you mean by this?
>
>
> On Tue, Apr 17, 2018 at 1:43 AM, Waldemar Horwat <waldemar at google.com>
> wrote:
>
>> On 04/13/2018 09:41 PM, Sultan wrote:
>>
>>>  >Writing your private field to an object that's not an instance of your
>>> class.
>>>  >and then invoking the above write method with a this value that's not
>>> an instance of A, such as a proxy.
>>>
>>> Given:
>>>
>>> class A {
>>>    private id = 0;
>>>    private method(value) {
>>>      return value;
>>>    }
>>>    write(value) {
>>>      private(this)["id"] = private["method"](value);
>>>    }
>>> }
>>>
>>> I imagine this means trying to do something along the lines of:
>>>
>>> (new A()).write.call({}, 'pawned');
>>>
>>> This would fail. The private syntax call site would be scoped to the
>>> provider class. For example imagine the current possible transpilation
>>> of
>>> this:
>>>
>>> ;(function (){
>>>    var registry = WeakMap();
>>>
>>>    function A () {
>>>      registry.set(this, {id: 0})
>>>    }
>>>    A.prototype.write: function () {
>>>      registry.get(this)["id"] =
>>> registry.get(this.constructor)["method"].call(this,
>>> value);
>>>    }
>>>
>>>    // shared(i.e private methods)
>>>    registry.set(A, {
>>>      method: function (value) {
>>>        return value;
>>>      }
>>>    });
>>>
>>>    return A
>>> })();
>>>
>>> Trying to do the the afore-mentioned forge here would currently fail
>>> along the lines of cannot read property "id" of  "undefined".
>>>
>>
>> OK, so that aspect of the proposal looks the same as the existing private
>> proposals — an instance has a fixed set of private fields which get
>> created
>> at object creation time.  There are tricky additional wrinkles when it
>> comes to inheritance, but you can look them up in the existing proposals.
>>
>> Are the only significant changes the different property naming syntax and
>> that you provide a way to map strings to private slots?  How do you deal
>> with inner nested classes wanting to refer to outer classes' private
>> fields?
>>
>>     Waldemar
>>
>