(Sorry for the triple-post, I keep pondering this proposal) Come to think
of it, you could do something pretty similar with the `??=` operator from
the logical assignments proposal:
```javascript
(((table ??= {}).user ??= {}).id ??= {}).type = 'int';
```
The main difference being that it tests for nullishness instead of whether
the LHS is a non-null object, but I think that's within the spirit of the
original proposal. It also lets you set a custom default value (like the
"getsert" function above). The shortfall of course is the accumulating
parentheses
On Sat, Apr 25, 2020 at 8:08 PM Jacob Bloom <[email protected]>
wrote:
> Is the Perl syntax opt-in like the proposed operator? Or does it happen on
> all accesses to nulls? If it's opt-in in JS, then it doesn't seem to me
> that it'd cause too much unexpected behavior, though it could be argued
> that it's ripe for abuse by new devs trying to avoid errors.
>
> Something that might be a more generalized middle ground (and could later
> assist in transpiling the !. operator) is a "getsert" (?) method in the
> standard library that takes a default value and sets it on the parent
> object if that property is currently unset:
>
> ```javascript
> Object.getsert = (obj, identifier, defaultvalue) => {
> if (!(identifier in obj)) obj[identifier] = defaultvalue;
> return obj[identifier];
> }
>
> const table = {};
> console.log('before getsert:', table.user); // undefined
> console.log('during getsert:', Object.getsert(table, 'user', 5)); // 5
> console.log('after getsert:', table.user); // 5
> ```
>
> ...I have concerns about such a method's usability though, since a getsert
> is far more verbose than a normal get. It'd be more convenient on
> Object.prototype (e.g. `table.getsert('user', 5)` ), but I assume that's a
> no-go.
>
> Oh also, I think the proposed syntax would collide with
> TypeScript's non-null assertion operator
> https://www.typescriptlang.org/docs/handbook/release-notes/typescript-2-0.html#non-null-assertion-operator
> --
> I don't know to what degree that's a concern when proposing new JS syntax
>
> On Sat, Apr 25, 2020 at 3:00 PM Joe Eagar <[email protected]> wrote:
>
>>
>> Anyone have ideas on more examples? It’s tempting to make a transpiler
>> plugin to see how it works in practice, but I’d like to see more examples
>> first. Thanks
>>
>> On Sat, Apr 25, 2020 at 1:12 PM Jacob Bloom <[email protected]>
>> wrote:
>>
>>> Maybe it would be less footgunny to support autovivification in a more
>>> class-based way, like Python does?
>>>
>>> ```javascript
>>> class AutoVivArray extends Array {
>>> [Symbol.getMissing](identifier) {
>>> /* if we're here, identifier is not an ownProperty
>>> * and is nowhere on the prototype chain */
>>> this[identifier] = new Whatever();
>>> return this[identifier];
>>> }
>>> }
>>> ```
>>>
>>> Though I can't see how that's much more useful than Proxies besides
>>> saving you a little boilerplate
>>>
>>> On Fri, Apr 24, 2020 at 3:23 PM Thomas Shinnick <[email protected]>
>>> wrote:
>>>
>>>> You are describing Perl's autovivification feature. Also possible (in
>>>> that syntax) for arrays and mixed object/array chains. I liked it, but many
>>>> saw it as a footgun. There was even a compile time module to turn off the
>>>> feature, if the coder wanted more caution. Having mentioned Perl I will
>>>> assume this is DOA?
>>>>
>>>> On Fri, Apr 24, 2020, 14:36 Tobias Buschor <[email protected]>
>>>> wrote:
>>>>
>>>>> Since we now have the "Optional Chaninig Operator" , perhaps a "Forced
>>>>> Chaining Operator" would also be worth considering.
>>>>> I, personally, could use it:
>>>>>
>>>>> let table;
>>>>> table!.user!.id!.type = 'int'
>>>>>
>>>>> will evaluate to:
>>>>>
>>>>> let table;
>>>>> if ( ! ( table instanceOf Object) ) table = {};
>>>>> if ( ! ( table.user instanceOf Object) ) table.user = {};
>>>>> if ( ! ( table.user.id instanceOf Object) ) table.user.id = {};
>>>>> table.user.id.type = 'int';
>>>>>
>>>>> Also to be noted:
>>>>> Sometimes a fallback to `Object.create(null)` or something other might
>>>>> be desirable.
>>>>> But since `{}` is syntactical sugar for
>>>>> `Object.create(Object.prototype)`, this would be consistent.
>>>>>
>>>>> _______________________________________________
>>>>> es-discuss mailing list
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>>>>> https://mail.mozilla.org/listinfo/es-discuss
>>>>>
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>>
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