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| // Here is an example of a plain old function that returns a promise. | |
| // Nothing magic about that. | |
| function sleep(sec) { | |
| return new Promise(function (resolve, reject) { | |
| setTimeout(function () { | |
| resolve(undefined); | |
| }, sec * 1000); | |
| }); | |
| } | |
| // Now, as requested, a generator that we're converting into a | |
| // function-that-returns-a-promise using the decorator co(). | |
| var g = co(function* () { | |
| yield sleep(0.3); | |
| console.log("at 0.3sec"); | |
| yield sleep(0.2); | |
| console.log("at 0.5sec"); | |
| yield sleep(0.4); | |
| console.log("done"); | |
| return "squeamish ossifrage"; | |
| }); | |
| // When we call g(), it returns a promise for | |
| // the generator's eventual return value. | |
| g().then(function (result) { | |
| console.log("promise resolved! the magic words are:", result); | |
| }); | |
| // And here is the definition of co(). | |
| function co(g) { | |
| return function(...args) { | |
| return new Promise(function (resolve, reject) { | |
| var gen = g(...args); | |
| function next(value) { | |
| var result; | |
| try { | |
| result = gen.next(value); | |
| } catch (exc) { | |
| reject(exc); | |
| return; | |
| } | |
| if (result.done) { | |
| resolve(result.value); | |
| return; | |
| } | |
| result.value.then(next, reject); | |
| } | |
| setTimeout(() => next(undefined), 0); | |
| }); | |
| }; | |
| } |
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