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Async utilities for node and the browser

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Async is a utility module which provides straight-forward, powerful functions for working with asynchronous JavaScript. Although originally designed for use with Node.js and installable via

npm i async
, it can also be used directly in the browser. A ESM/MJS version is included in the main
package that should automatically be used with compatible bundlers such as Webpack and Rollup.

A pure ESM version of Async is available as


For Documentation, visit

For Async v1.5.x documentation, go HERE

// 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); });

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) })

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