Try this... It will only seal if calling new. The subclasses will still
need to seal though.
```js
class Test {
constructor() {
this.x = 1;
if(new.target === Test) {
Object.seal(this);
}
}
}
```
On Fri, Mar 18, 2016 at 9:57 AM, Brian Barnes <[email protected]> wrote:
> Great, glad to hear that's coming! I think sealing is a fine solution,
> it'll do what I want and doesn't cause fits for the engine makers.
>
> That said, it has one problem -- base classes. You can't seal them
> because the constructor in the extended class would fail (I tried it) and
> so the base classes would always have to remain unsealed which means you
> either (1) understand that or (2) always use an extended class if you care
> for level of code safety.
>
> [>] Brian
>
>
> On 3/18/2016 11:50 AM, kdex wrote:
>
>> Brian, Your first example isn't too far from ES2017. Leave away the
>> `let`s and seal it, and you got:
>>
>> ```js
>> "use strict";
>> class Test {
>> x = 1;
>> y = 2;
>> constructor() {
>> Object.seal(this);
>> this.z = 3; // TypeError
>> }
>> }
>> ```
>> You can already use this using transpilers (at least babel supports it).
>>
>> On 18.03.2016 15:39, Brian Barnes wrote:
>>
>>> Ugh, well, I guess I typed a lot of stuff for nothing! And by the
>>> look of their experiment, what I wanted was actually one of the major
>>> blockers.
>>>
>>> It seems classes will really need a more standard type of syntax (non
>>> static) before you could actually achieve this, and might be a bridge
>>> too far for javascript:
>>>
>>> class test
>>> {
>>> let x=1;
>>> let y=2;
>>> constructor() {}
>>> func() { this.z=2; } // syntax error
>>> }
>>>
>>> Though it could be kind of faked by some kind of reverse hoisting,
>>> i.e., rebuilding the code inside the engine:
>>>
>>> class test
>>> {
>>> constructor()
>>> {
>>> this.x=1;
>>> this.y=2;
>>> // stuff that was in the constructor
>>> Object.seal(this);
>>> }
>>> ...
>>> }
>>>
>>> [>] Brian
>>>
>>> On 3/18/2016 10:04 AM, Sébastien Doeraene wrote:
>>>
>>>> Hi,
>>>>
>>>> The Strong Mode experiment was canceled:
>>>> https://groups.google.com/forum/#!topic/strengthen-js/ojj3TDxbHpQ
>>>>
>>>> Cheers,
>>>> Sébastien
>>>>
>>>> On Fri, Mar 18, 2016 at 3:59 PM, kdex <[email protected]
>>>> <mailto:[email protected]>> wrote:
>>>>
>>>> Already considered and to be implemented via strong mode IIRC.
>>>>
>>>> On 18.03.2016 14:36, Brian Barnes wrote:
>>>>
>>>> I know properties on classes are getting a look over for the
>>>> next iteration (last I checked) and I understand javascript is
>>>> obviously a different language then other oo languages with a
>>>> different foundation, but I bring this up for it's usage in
>>>> producing stricter code that reduces errors and is easier to
>>>> analyze. A vote for this if anybody considered it!
>>>>
>>>> class Test
>>>> {
>>>>
>>>> constructor()
>>>> {
>>>> this.x=1;
>>>> }
>>>>
>>>> func1()
>>>> {
>>>> this.y=2;
>>>> }
>>>>
>>>> func2()
>>>> {
>>>> console.log(this.x+','+this.y);
>>>> }
>>>> }
>>>>
>>>> var test1=new Test();
>>>> test1.func1();
>>>> test2.func2(); // outputs 1,2
>>>>
>>>> var test2=new Test();
>>>> test2.func(); // outputs 1,undefined
>>>>
>>>> I know classes contents are meant to be in strict mode, and I
>>>> thinking that only allowing properties to be created in the
>>>> constructor (or eventually static properties on the class
>>>> itself) would make a system less prone to the conditions like
>>>> you see above. Basically, func1() would produce a error when
>>>> run.
>>>>
>>>> I can see why this type of initialization of properties could be
>>>> desired, though, especially as it reflect the way it would have
>>>> worked if you used a function instead of a class.
>>>>
>>>> [>] Brian
>>>> _______________________________________________
>>>> es-discuss mailing list
>>>> [email protected] <mailto:[email protected]>
>>>> https://mail.mozilla.org/listinfo/es-discuss
>>>>
>>>>
>>>> _______________________________________________
>>>> es-discuss mailing list
>>>> [email protected] <mailto:[email protected]>
>>>> https://mail.mozilla.org/listinfo/es-discuss
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> es-discuss mailing list
>>>> [email protected]
>>>> https://mail.mozilla.org/listinfo/es-discuss
>>>>
>>>> _______________________________________________
>>> es-discuss mailing list
>>> [email protected]
>>> https://mail.mozilla.org/listinfo/es-discuss
>>>
>>
>> _______________________________________________
>> es-discuss mailing list
>> [email protected]
>> https://mail.mozilla.org/listinfo/es-discuss
>>
> _______________________________________________
> es-discuss mailing list
> [email protected]
> https://mail.mozilla.org/listinfo/es-discuss
>
_______________________________________________
es-discuss mailing list
[email protected]
https://mail.mozilla.org/listinfo/es-discuss
