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| ; | |
| const pLimit = require('p-limit'); | |
| class EndError extends Error { | |
| constructor(value) { | |
| super(); | |
| this.value = value; | |
| } | |
| } | |
| // The input can also be a promise, so we await it | |
| const testElement = async (element, tester) => tester(await element); | |
| // The input can also be a promise, so we `Promise.all()` them both | |
| const finder = async element => { | |
| const values = await Promise.all(element); | |
| if (values[1] === true) { | |
| throw new EndError(values[0]); | |
| } | |
| return false; | |
| }; | |
| const pLocate = async (iterable, tester, options) => { | |
| options = { | |
| concurrency: Infinity, | |
| preserveOrder: true, | |
| ...options | |
| }; | |
| const limit = pLimit(options.concurrency); | |
| // Start all the promises concurrently with optional limit | |
| const items = [...iterable].map(element => [element, limit(testElement, element, tester)]); | |
| // Check the promises either serially or concurrently | |
| const checkLimit = pLimit(options.preserveOrder ? 1 : Infinity); | |
| try { | |
| await Promise.all(items.map(element => checkLimit(finder, element))); | |
| } catch (error) { | |
| if (error instanceof EndError) { | |
| return error.value; | |
| } | |
| throw error; | |
| } | |
| }; | |
| module.exports = pLocate; | |
| // TODO: Remove this for the next major release | |
| module.exports.default = pLocate; | |