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createAsyncFunction.js · GitHub
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function createAsyncFunction(fn) { | |
return function () { | |
var gen = fn.apply(this, arguments); | |
return new Promise(function (resolve, reject) { | |
function step(key, arg) { | |
try { | |
var info = gen[key](arg); | |
var value = info.value; | |
} catch (error) { | |
reject(error); | |
return; | |
} | |
if (info.done) { | |
resolve(value); | |
} else { | |
return Promise.resolve(value).then(function (value) { | |
step("next", value); | |
}, function (err) { | |
step("throw", err); | |
}); | |
} | |
} | |
return step("next"); | |
}); | |
}; | |
} |
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Hello Jake!
I don't even know how I got to this function (I've got dozens of tabs open while I research asynchronous javascript). At first I found it quite cryptic, but I took figuring it out as a challenge.
So after a few days tinkering with it I believe It takes a generator function, then returns a function that accepts arguments that might be used by such generator function to craft an Iterable. Then it creates said iterable (as a generator object), then returns a pending promise that will start an iteration sequence and only settle when an iteration throws an error, returns a rejected promise, or is the last one.
Now here's the motivation for this comment: I believe the return statements on lines 23 and 16 are both unnecessary/inert. The reasoning being:
For line 23:
For line 16:
TL;DR: For didactic purposes I removed the return statements in lines 16 & 23, kept the returned expressions. Code worked the same.
I don't even think you'll be bothered with this, but still serves me as an exercise, though.
Loved your event loop talk in JSConf.Asia!
Cheers