| '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 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; |