caolan/async

---

caolan/async.json

{
  "createdAt": "2010-06-01T21:01:30Z",
  "defaultBranch": "master",
  "description": "Async utilities for node and the browser",
  "fullName": "caolan/async",
  "homepage": "http://caolan.github.io/async/",
  "language": "JavaScript",
  "name": "async",
  "pushedAt": "2025-11-24T15:28:33Z",
  "stargazersCount": 28219,
  "topics": [
    "async",
    "callbacks",
    "javascript"
  ],
  "updatedAt": "2025-11-23T09:48:21Z",
  "url": "https://github.com/caolan/async"
}

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. An ESM/MJS version is included in the main async package that should automatically be used with compatible bundlers such as Webpack and Rollup.

A pure ESM version of Async is available as async-es.

For Documentation, visit https://caolan.github.io/async/

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)
})