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- 'use strict';
- const pMap = (iterable, mapper, options) => new Promise((resolve, reject) => {
- options = Object.assign({
- concurrency: Infinity
- }, options);
- if (typeof mapper !== 'function') {
- throw new TypeError('Mapper function is required');
- }
- const {concurrency} = 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 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) {
- resolve(ret);
- }
- return;
- }
- resolvingCount++;
- Promise.resolve(nextItem.value)
- .then(element => mapper(element, i))
- .then(
- value => {
- ret[i] = value;
- resolvingCount--;
- next();
- },
- error => {
- isRejected = true;
- reject(error);
- }
- );
- };
- 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;
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