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[](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.jsdelivr.com/package/npm/async)
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Async 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.
A pure ESM version of Async is available as [`async-es`](https://www.npmjs.com/package/async-es).
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)
})
```
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