I've created a gist with a more realistic example and a way to do this today: https://gist.github.com/mariusGundersen/985189540541189ca80f60b59fa343ac
Notice that the `with` keyword is followed by an expression, it's not limited to a variable binding. This is similar to how a `for(let i=0; i<10; i++)` statement has the `i<10` expression as a test. On Mon, Aug 21, 2017 at 1:07 PM, Michał Wadas <[email protected]> wrote: > Communication by mutating shared variables is not a solution. > > On 21 Aug 2017 12:47 pm, "Naveen Chawla" <[email protected]> wrote: > >> Currently you can set one or more variables outside the scope of the >> generator function during iteration, which the generator function can read. >> Is this so bad? >> >> On Mon, 21 Aug 2017 at 15:24 Marius Gundersen <[email protected]> >> wrote: >> >>> Generators today can both "send" a value and "receive" a value from >>> their consumer, so they can act as an interactive iterable. See for example >>> [fibonacci with reset](https://developer.mozil >>> la.org/en/docs/Web/JavaScript/Guide/Iterators_and_ >>> Generators#Advanced_generators) >>> >>> While generators are "producers" of values, the for-of statement acts as >>> a "consumer" of these values. But unfortunately the for-of cannot send >>> values back to the generator: >>> >>> ```js >>> for(const value of fibonacci()){ >>> console.log(value); >>> //no way to reset it :( >>> } >>> ``` >>> >>> I propose a for-of-with statement, like so: >>> >>> ```js >>> let feedback = false; >>> for(const value of fibonacci() with feedback){ >>> console.log(value) >>> feedback = value == 8; >>> } >>> ``` >>> >>> Note that the variable has to be defined before the for-of-with >>> statement, but the initial value will not be seen inside the generator >>> until [function.sent](https://github.com/allenwb/ESideas/blob/ >>> master/Generator%20metaproperty.md) is implemented. >>> >>> The babel output of the for-of-with statement would be the following: >>> >>> ```js >>> var reset = false; >>> var _iteratorNormalCompletion = true; >>> var _didIteratorError = false; >>> var _iteratorError = undefined; >>> >>> try { >>> for (var _iterator = fibonacci()[Symbol.iterator](), _step; >>> !(_iteratorNormalCompletion = (_step = _iterator.next(reset)).done); >>> _iteratorNormalCompletion = true) { >>> var value = _step.value; >>> >>> console.log(value); >>> reset = value == 8; >>> } >>> } catch (err) { >>> _didIteratorError = true; >>> _iteratorError = err; >>> } finally { >>> try { >>> if (!_iteratorNormalCompletion && _iterator.return) { >>> _iterator.return(); >>> } >>> } finally { >>> if (_didIteratorError) { >>> throw _iteratorError; >>> } >>> } >>> } >>> ``` >>> >>> Marius Gundersen >>> _______________________________________________ >>> 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
