Sorry to show up late but just wanted to point out that shipping this feature with the ! symbol would break TypeScript, which has this operator but only at compile time for forcing the compiler to believe that a nullable value will be non-null at the time of execution (assuming you have some information the compiler doesn't). It has no runtime effect of creating objects.
Le mar. 5 mai 2020 07 h 36, Tobias Buschor <[email protected]> a écrit : > I think that would work, but the many nested brackets bother me. > > Am Mo., 27. Apr. 2020 um 14:23 Uhr schrieb Naveen Chawla < > [email protected]>: > >> Can someone confirm if the following nullish coalescing assignment >> operator proposal example would work for this, or would it produce some >> other kind of result?: >> >> ```js >> (((table ??= {}).user ??= {}).id ??= {}).type = 'int' >> ``` >> Regardless, I'm not a TC39 member but I would definitely be against >> forcing a type during assignment if "not already that type", as recommended >> in the original post. I think this could be a source of serious bugs in >> particular when an existing type structure has been miscalculated by the >> person using that "force type" operator. So regardless, I would prefer any >> shorthand to only assign to object/array etc. "if nullish". This would >> raise errors if already of an unexpected type, but I would much prefer that >> over forcing a new structure where an existing one already exists (and >> overwriting data). >> >> On Mon, 27 Apr 2020 at 10:17, Max Fechner <[email protected]> wrote: >> >>> How about something like >>> >>> >>> >>> table{}.user{}.id{}.type = ‘int’ >>> >>> >>> >>> this syntax could be used for arrays, too: >>> >>> >>> >>> table{}.userList[].push(‘Jane Doe’) >>> >>> >>> >>> >>> >>> >>> >>> *From: *es-discuss <[email protected]> on behalf of Jacob >>> Bloom <[email protected]> >>> *Date: *Monday, 27April, 2020 at 02:23 >>> *To: *es-discuss <[email protected]> >>> *Subject: *Re: Proposal: Forced Chaining Operator "!." >>> >>> >>> >>> (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 >>> [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 >> > > > -- > Freundliche Grüsse > Tobias Buschor > > schwups GmbH > Hauptstr. 33 > 9424 Rheineck/SG > > +41 76 321 23 21 > _______________________________________________ > 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
