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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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| <!-- |
| |Linux|Windows|MacOS| |
| |-|-|-| |
| |[](https://dev.azure.com/caolanmcmahon/async/_build/latest?definitionId=1&branchName=master) | [](https://dev.azure.com/caolanmcmahon/async/_build/latest?definitionId=1&branchName=master) | [](https://dev.azure.com/caolanmcmahon/async/_build/latest?definitionId=1&branchName=master)| --> |
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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. An ESM/MJS version is included in the main `async` package that should automatically be used with compatible bundlers such as Webpack and Rollup. |
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| A pure ESM version of Async is available as [`async-es`](https://www.npmjs.com/package/async-es). |
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| For Documentation, visit <https://caolan.github.io/async/> |
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| *For Async v1.5.x documentation, go [HERE](https://github.com/caolan/async/blob/v1.5.2/README.md)* |
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| ```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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