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- 'use strict';
- const pLimit = require('p-limit');
-
- class EndError extends Error {
- constructor(value) {
- super();
- this.value = value;
- }
- }
-
- // the input can also be a promise, so we `Promise.all()` them both
- const finder = el => Promise.all(el).then(val => val[1] === true && Promise.reject(new EndError(val[0])));
-
- module.exports = (iterable, tester, opts) => {
- opts = Object.assign({
- concurrency: Infinity,
- preserveOrder: true
- }, opts);
-
- const limit = pLimit(opts.concurrency);
-
- // start all the promises concurrently with optional limit
- const items = Array.from(iterable).map(el => [el, limit(() => Promise.resolve(el).then(tester))]);
-
- // check the promises either serially or concurrently
- const checkLimit = pLimit(opts.preserveOrder ? 1 : Infinity);
-
- return Promise.all(items.map(el => checkLimit(() => finder(el))))
- .then(() => {})
- .catch(err => err instanceof EndError ? err.value : Promise.reject(err));
- };
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