1  'use strict';
 2  const pLimit = require('p-limit');
 3  
 4  class EndError extends Error {
 5  	constructor(value) {
 6  		super();
 7  		this.value = value;
 8  	}
 9  }
10  
11  // The input can also be a promise, so we await it
12  const testElement = async (element, tester) => tester(await element);
13  
14  // The input can also be a promise, so we `Promise.all()` them both
15  const finder = async element => {
16  	const values = await Promise.all(element);
17  	if (values[1] === true) {
18  		throw new EndError(values[0]);
19  	}
20  
21  	return false;
22  };
23  
24  const pLocate = async (iterable, tester, options) => {
25  	options = {
26  		concurrency: Infinity,
27  		preserveOrder: true,
28  		...options
29  	};
30  
31  	const limit = pLimit(options.concurrency);
32  
33  	// Start all the promises concurrently with optional limit
34  	const items = [...iterable].map(element => [element, limit(testElement, element, tester)]);
35  
36  	// Check the promises either serially or concurrently
37  	const checkLimit = pLimit(options.preserveOrder ? 1 : Infinity);
38  
39  	try {
40  		await Promise.all(items.map(element => checkLimit(finder, element)));
41  	} catch (error) {
42  		if (error instanceof EndError) {
43  			return error.value;
44  		}
45  
46  		throw error;
47  	}
48  };
49  
50  module.exports = pLocate;
51  // TODO: Remove this for the next major release
52  module.exports.default = pLocate;