/
index.js
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/
index.js
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'use strict';
const AggregateError = require('aggregate-error');
const pMap = (iterable, mapper, options) => new Promise((resolve, reject) => {
options = Object.assign({
concurrency: Infinity,
stopOnError: true
}, options);
if (typeof mapper !== 'function') {
throw new TypeError('Mapper function is required');
}
const {concurrency, stopOnError} = options;
if (!(typeof concurrency === 'number' && concurrency >= 1)) {
throw new TypeError(`Expected \`concurrency\` to be a number from 1 and up, got \`${concurrency}\` (${typeof concurrency})`);
}
const ret = [];
const errors = [];
const iterator = iterable[Symbol.iterator]();
let isRejected = false;
let isIterableDone = false;
let resolvingCount = 0;
let currentIndex = 0;
const next = () => {
if (isRejected) {
return;
}
const nextItem = iterator.next();
const i = currentIndex;
currentIndex++;
if (nextItem.done) {
isIterableDone = true;
if (resolvingCount === 0) {
if (!stopOnError && errors.length !== 0) {
reject(new AggregateError(errors));
} else {
resolve(ret);
}
}
return;
}
resolvingCount++;
Promise.resolve(nextItem.value)
.then(element => mapper(element, i))
.then(
value => {
ret[i] = value;
resolvingCount--;
next();
},
error => {
if (stopOnError) {
isRejected = true;
reject(error);
} else {
errors.push(error);
resolvingCount--;
next();
}
}
);
};
for (let i = 0; i < concurrency; i++) {
next();
if (isIterableDone) {
break;
}
}
});
module.exports = pMap;
// TODO: Remove this for the next major release
module.exports.default = pMap;