I'd prefer to have it in slice-notation https://github.com/tc39/proposal-slice-notation/issues/1#issuecomment-522227270
```js [...0:8] // [0,1,2,3,4,5,6,7] ``` On Mon, Aug 19, 2019 at 9:34 AM Naveen Chawla <naveen.c...@gmail.com> wrote: > I like it. I might prefer it in square brackets e.g. [ x ... y ] ? > > On Sun, 18 Aug 2019 at 23:24, Artem Kobzar <a.kobzar....@gmail.com> wrote: > >> ### Proposal: Range Expression >> >> The proposal based on one of the worst things in JavaScript Arrays. >> >> If i as developer want to make sequence of some numbers or characters >> then i need to use weird methods like `Array.from`, manual filling or >> imperative-style array filling. >> >> ```js >> const group1 = [1, 2, 3, 4, 5, ...]// manual filling >> const group2= Array.from({ length: 15 }).map((_, i) => i + 1); >> const group3 = []; >> for (let i = 0; i < 15; i++) group3[i] = i + 1; >> ``` >> >> This ways to describe range sequence is huge and unreadable. >> >> >> So, my proposal is: range expression which help to create lazy iterable >> range sequence in declarative way. >> >> ```js >> const group0 = 1...15; // from 1 to 15 >> const group1 = 15...1; // from 15 to 1 >> const group2 = 1n...15n // from 'a' to 'z' >> const group3 = 'a'...'z' // from 'a' to 'z' >> const group4 = 82... // lazy collection of numbers >> >> for (const odd of 1...85) { >> // ... >> } >> >> // in combination with https://github.com/tc39/proposal-iterator-helpers >> const allEven = (1...100).filter(isEven); >> ``` >> >> So, this operator is syntax sugar for the next generator which create >> lazy iterable sequence: >> >> ```js >> function* range(start, end, second) { >> validate(start, end, second)// type assertion of start, second and end >> const step = difference(start, second); // difference calculation >> let current = start; >> while(isNotEnd(current, end)) { // logic for negative step and >> different types >> yield current; >> current = next(current, step); // function which change current >> number | bigint | string by difference >> } >> } >> ``` >> _______________________________________________ >> es-discuss mailing list >> es-discuss@mozilla.org >> https://mail.mozilla.org/listinfo/es-discuss >> > _______________________________________________ > es-discuss mailing list > es-discuss@mozilla.org > https://mail.mozilla.org/listinfo/es-discuss >
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