Hi Cyril,
With the syntax you propose what would be the way to to this:
```
const source = {foo: 1, bar: 2};
const result = {foo: source.foo, bar: source.bar, buzz: 3}
```
?ср, 29 мая 2019 г. в 20:14, Cyril Auburtin <[email protected]>: > What I'd like is this syntax: > > ```js > let o={a:1, b:2, c:3}; > o.{a, b} // would be {a: 1, b: 2} > ``` > > On Tue, May 28, 2019 at 9:13 PM Григорий Карелин <[email protected]> > wrote: > >> Here are another examples, where "destructuring picking" I suggest whould >> be helpful. >> ==1A Now (redux related) >> ``` >> function mapStateToProps({user: {firstName, lastName}, common: >> {currentPageURL: url}}) { >> return {firstName, lastName, url}; >> } >> ``` >> ==1B Proposal >> ``` >> function mapStateToProps(state) { >> return {{firstName, lastName from state.user}, {currentPageURL as url >> from state.common}}; >> } >> ``` >> >> Shorter! >> >> ==2A Now >> ``` >> async function saveNewUserName(name) { >> const {name} = await sendToServer({name}); >> >> return {ok: true, payload: {name}}; // oh wait, which name is it again? >> Argument or response? >> } >> ``` >> == 2B Proposal >> ``` >> async function saveNewUserName(name) { >> const resp = await sendToServer({name}); >> >> return {ok: true, {name from response}}; >> } >> ``` >> No accidental shadowing. >> >> I know, I know, you can achieve all that without new syntax, via naming >> your variables properly and using long explicit expressions. But I think >> some sugar won't hurt. >> After all, remember destructuring? There's no reason to use it other than >> it's cool and short and expressive. >> >> >> вт, 28 мая 2019 г. в 21:49, guest271314 <[email protected]>: >> >>> ``` >>>>> let obj = {otherData: "other data"}; >>>>> ({firstName:obj.firstName, lastName:obj.lastName} = user.profile); >>>>> ``` >>>> >>>> I don't understand this. >>>> >>>> >>> >>> https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment#Assigning_to_new_variable_names >>> >>> He's looking for a terser >>> >>> >>> Is the proposal to golf destructuring assignment? >>> >>> The proposed destructuring assignment syntax example is 25 characters >>> less than the non-destructing assignment example, which is terser. >>> >>> One observation about the proposed syntax is that the values set at the >>> target object would be set from the identifier on the left side of >>> ```from``` which is similar to >>> >>> ``` >>> var o = {x:1}; >>> console.log(o.x = 2); // 2 >>> ``` >>> >>> though how will the property name be set at the object at target object >>> instead of `{"2":2}`? How does the engine know when the expected result is >>> ```{"x":2}``` and not ```{"2":2}```? Certainly such functionality can be >>> designed, for example, using the proposed key word ```from```. >>> >>> If more terse code is one of the features that would be achieved, why >>> are the wrapping `{}` around ```from`` necessary? >>> >>> > moire elegant way to do it, >>> >>> "elegant" is subjective >>> >>> > which hopefully would be moire semantic, less bug-prone, more >>> type-checkable (for typed variants of the language), more reminiscent of >>> existing syntax such as deconstruction, and potentially more optimizable by >>> engines. >>> >>> What is bug prone about the code examples at OP? >>> >>> This proposal would resolve the issue of currently, in general, having >>> to write the property name twice. >>> >>> >>> >>> On Tue, May 28, 2019 at 2:47 PM Bob Myers <[email protected]> wrote: >>> >>>> ``` >>>>> let obj = {otherData: "other data"}; >>>>> ({firstName:obj.firstName, lastName:obj.lastName} = user.profile); >>>>> ``` >>>>> >>>> >>>> I don't understand this. >>>> >>>> >>>>> Alternatively there are various approaches which can be used to get >>>>> only specific properties from an abject and set those properties and >>>>> values >>>>> at a new object without using destructing assignment. >>>>> >>>>> Using object rest and ```reduce()``` >>>>> >>>>> ```let obj = {otherData: "other data", ...["firstName", >>>>> "lastName"].reduce((o, prop) => (o[prop] = user.profile[prop], o), >>>>> {})};``` >>>>> >>>>> `Object.assign()`, spread syntax and `map()` >>>>> >>>>> ```let obj = Object.assign({otherData: "other data"}, ...["firstName", >>>>> "lastName"].map(prop => ({[prop]:user.profile[prop]})));``` >>>>> >>>> >>>> As the words "syntactic sugar" in the subject of the thread make clear, >>>> the OP is not merely looking for ways to assign one object's property into >>>> another--there are many ways to do that. He's looking for a terser, moire >>>> elegant way to do it, which hopefully would be moire semantic, less >>>> bug-prone, more type-checkable (for typed variants of the language), more >>>> reminiscent of existing syntax such as deconstruction, and potentially more >>>> optimizable by engines. >>>> >>>> Bob >>>> _______________________________________________ >>>> 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 >>> >> >> >> -- >> С уважением, >> Карелин Григорий >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> > -- С уважением, Карелин Григорий
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