Another pattern it could be useful in is with, say, nosql dbs where
something might be an object or id reference:
```
const fooId = foo<?.id;
```
On Thu, 5 Sep 2019, 23:03 Andrea Giammarchi, <andrea.giammar...@gmail.com>
wrote:
> Another use case that I believe will be common is the following one:
>
> ```js
> // current state of the art
> const result = dbQuery(data)?.rows ?? 'did it just failed or what?';
>
> // VS the "mice operator"
> const result = dbQuery(data)<?.rows;
>
> // if it was rows
> if (Array.isArray(result))
> console.log(result);
> else if (result instanceof Error)
> console.error(result.message);
> else
> console.warn(`unexpected result: ${result}`);
> ```
>
> Ideally, the "mice" should grant chaining up to its latest presence, but I
> wouldn't know right now how to reference to it ...
>
> ```js
> // if no ?? is needed, this might work
> const result = dbQuery(data)<?.rows?.data?.entry;
>
> // if ?? is needed, no idea how to back-reference the latest successfull
> "mice" result
> ```
>
>
>
>
> On Thu, Sep 5, 2019 at 11:44 PM Tab Atkins Jr. <jackalm...@gmail.com>
> wrote:
>
>> On Thu, Sep 5, 2019 at 2:39 PM Andrea Giammarchi
>> <andrea.giammar...@gmail.com> wrote:
>> >
>> > This is basically a solution to a common problem we have these days,
>> where modules published in the wild might have a `default` property, to
>> support ESM logic, or not.
>> >
>> > ```js
>> > // current optional chaining logic
>> > const imported = exported?.default ?? exported;
>> >
>> > // my "mice operator" proposal
>> > const imported = exported<?.default;
>> > ```
>> >
>> > Semantically speaking, not only `<?` actually looks like a mice, it
>> also points at its previous value in case the chaining didn't work.
>> >
>> > Beside the basic example, the "mice operator" might save CPU cycles
>> when it comes to involving more complex expressions, i.e.
>> >
>> > ```js
>> > // current "solution"
>> > const thing = require('thing')?.default ?? require('thing');
>> >
>> > // mice operator
>> > const thing = require('thing')<?.default;
>> > ```
>> >
>> > This is also easily tranpilable, so kinda a no-brainer for modern dev
>> tools to bring in.
>> >
>> > TL;DR specially for cases where an accessed property should fallback to
>> its source, this operator might save both typing and CPU time whenever it's
>> needed.
>>
>> I find it a rather curious pattern, that I'd never seen before! Is it
>> used in anything besides this ESM-compat thing you're talking about?
>>
>> (Saving CPU cycles is not a convincing argument; it's trivial to write
>> such a line over two declarations and avoid any expensive
>> recomputations.)
>>
>> ~TJ
>>
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