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Return Promise if callback is not provided? #1515
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Historically, However, with the new |
I've thought about this, and experimented with it a bit. People are going to want to Also, some Async methods would be pretty silly with async/await, e.g. |
When using Async I sort of naturally assumed the return of a Promise. It was only at the dis-functioning of my code and my routine rtfm moment that I noticed the callback structure. The above would be very welcome since it would keep code as uniform ES7 as possible. |
I agree that this would be useful. In the interim, if anyone is stuck right now, I found this article good for explaining how to write a forEach loop with await. |
Finally dug out my old experiment: #1526 |
+1 |
function makeAsync() {
if (arguments.length < 3) return; // wrong params, not run or throw exception here!
let fixParams = {};
let paramLength = arguments.length;
let method = arguments[0];
for (let i = 1; i < arguments.length; i++) {
fixParams[(i - 1)] = arguments[i];
}
return new Promise((resolve, reject) => {
const callback = (err, result) => {
if (err) return reject(err);
return resolve(result);
};
fixParams[paramLength - 1] = callback;
fixParams.length = paramLength;
method.apply(null, fixParams);
});
} example1: await makeAsync(async.each, openFiles, async (file) => {
await asyncOperation(file);
}); example2: const foo = async () => {
const arr = Array.from({ length: 1000 }, (v, i) => i);
const transformedArr = await makeAsync(async.mapLimit, arr, 100, async (v) => {
return await Promise.resolve(v * 2);
});
console.log(transformedArr);
} |
@tritoanst, your promisify function is overhead. It may be easier: function promisify(original) {
return function (...args) {
return new Promise((resolve, reject) => {
args.push((err, result) => {
if (err) {
reject(err);
} else {
resolve(result);
}
});
original.apply(this, args);
});
};
}
const foo = async () => {
const arr = Array.from({ length: 1000 }, (v, i) => i);
const transformedArr = await promisify(async.mapLimit)(arr, 100, async (v) => {
return v * 2; // `return await` is redundant
});
console.log(transformedArr);
}; |
Nice to have in ES2017 async/await development
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