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It is analog of [Bluebird.map with concurency](http://bluebirdjs.com/docs/api/promise.map.html) But with [correct start order](https://github.com/petkaantonov/bluebird/issues/847).
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function ownMap(arr, cb, {concurrency} = {}) { | |
if (!concurrency || concurrency < 1) { | |
return ownMap(arr, cb, {concurrency: Number.POSITIVE_INFINITY}) | |
} | |
const arrLength = arr.length; | |
const batchPromises = new Array(arrLength); | |
let currentTaskNumber = 0; | |
return new Promise((resolve, reject) => { | |
function endOneMore(result) { | |
if (currentTaskNumber === arrLength) { | |
Promise.all(batchPromises) | |
.then(resolve); | |
} | |
if (currentTaskNumber < arrLength) { | |
startOneMore(); | |
} | |
return result; | |
} | |
function startOneMore() { | |
batchPromises[currentTaskNumber] = cb(arr[currentTaskNumber]) | |
.then(endOneMore, reject); | |
currentTaskNumber++; | |
} | |
arr.slice(0, concurrency) | |
.map((v, i) => startOneMore(i)); | |
}); | |
} | |
// test | |
const array = (new Array(10)).fill(0).map((v, k) => k); | |
ownMap( | |
array, | |
(numb) => { | |
console.error(numb, 'started', numb); | |
const time = Math.round(Math.random() * 900) + 100; | |
return (new Promise(resolve => setTimeout(resolve, time))) | |
// .then(() => console.error(numb, 'ended', numb)) | |
.then(() => `${numb} - ${time}`); | |
}, | |
{concurrency: 3} | |
).then((arr) => console.log('finished all', arr.length, arr)); |
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0 'started' 0 | |
1 'started' 1 | |
2 'started' 2 | |
3 'started' 3 | |
4 'started' 4 | |
5 'started' 5 | |
6 'started' 6 | |
7 'started' 7 | |
8 'started' 8 | |
9 'started' 9 | |
finished all 10 [ '0 - 284', | |
'1 - 327', | |
'2 - 316', | |
'3 - 900', | |
'4 - 643', | |
'5 - 167', | |
'6 - 708', | |
'7 - 622', | |
'8 - 870', | |
'9 - 536' ] |
Author
tomfun
commented
Sep 18, 2017
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