 [](https://travis-ci.org/caolan/async) [](https://www.npmjs.com/package/async) [](https://coveralls.io/r/caolan/async?branch=master) [](https://gitter.im/caolan/async?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [](https://www.libhive.com/providers/npm/packages/async) [](https://www.jsdelivr.com/package/npm/async) Async is a utility module which provides straight-forward, powerful functions for working with [asynchronous JavaScript](http://caolan.github.io/async/global.html). Although originally designed for use with [Node.js](https://nodejs.org/) and installable via `npm install --save async`, it can also be used directly in the browser. This version of the package is optimized for the Node.js environment. If you use Async with webpack, install [`async-es`](https://www.npmjs.com/package/async-es) instead. For Documentation, visit <https://caolan.github.io/async/> *For Async v1.5.x documentation, go [HERE](https://github.com/caolan/async/blob/v1.5.2/README.md)* ```javascript // for use with Node-style callbacks... var async = require("async"); var obj = {dev: "/dev.json", test: "/test.json", prod: "/prod.json"}; var configs = {}; async.forEachOf(obj, (value, key, callback) => { fs.readFile(__dirname + value, "utf8", (err, data) => { if (err) return callback(err); try { configs[key] = JSON.parse(data); } catch (e) { return callback(e); } callback(); }); }, err => { if (err) console.error(err.message); // configs is now a map of JSON data doSomethingWith(configs); }); ``` ```javascript var async = require("async"); // ...or ES2017 async functions async.mapLimit(urls, 5, async function(url) { const response = await fetch(url) return response.body }, (err, results) => { if (err) throw err // results is now an array of the response bodies console.log(results) }) ```