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13
14Async is a utility module which provides straight-forward, powerful functions for working with [asynchronous JavaScript](http://caolan.github.io/async/v3/global.html). Although originally designed for use with [Node.js](https://nodejs.org/) and installable via `npm i async`, it can also be used directly in the browser.  A ESM/MJS version is included in the main `async` package that should automatically be used with compatible bundlers such as Webpack and Rollup.
15
16A pure ESM version of Async is available as [`async-es`](https://www.npmjs.com/package/async-es).
17
18For Documentation, visit <https://caolan.github.io/async/>
19
20*For Async v1.5.x documentation, go [HERE](https://github.com/caolan/async/blob/v1.5.2/README.md)*
21
22
23```javascript
24// for use with Node-style callbacks...
25var async = require("async");
26
27var obj = {dev: "/dev.json", test: "/test.json", prod: "/prod.json"};
28var configs = {};
29
30async.forEachOf(obj, (value, key, callback) => {
31    fs.readFile(__dirname + value, "utf8", (err, data) => {
32        if (err) return callback(err);
33        try {
34            configs[key] = JSON.parse(data);
35        } catch (e) {
36            return callback(e);
37        }
38        callback();
39    });
40}, err => {
41    if (err) console.error(err.message);
42    // configs is now a map of JSON data
43    doSomethingWith(configs);
44});
45```
46
47```javascript
48var async = require("async");
49
50// ...or ES2017 async functions
51async.mapLimit(urls, 5, async function(url) {
52    const response = await fetch(url)
53    return response.body
54}, (err, results) => {
55    if (err) throw err
56    // results is now an array of the response bodies
57    console.log(results)
58})
59```
60