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