60 lines
3.1 KiB
Markdown
60 lines
3.1 KiB
Markdown
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[](https://www.npmjs.com/package/async)
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[](https://coveralls.io/r/caolan/async?branch=master)
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[](https://gitter.im/caolan/async?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
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[](https://www.jsdelivr.com/package/npm/async)
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<!--
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|Linux|Windows|MacOS|
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|[](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
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// for use with Node-style callbacks...
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var async = require("async");
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var obj = {dev: "/dev.json", test: "/test.json", prod: "/prod.json"};
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var configs = {};
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async.forEachOf(obj, (value, key, callback) => {
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fs.readFile(__dirname + value, "utf8", (err, data) => {
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if (err) return callback(err);
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try {
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configs[key] = JSON.parse(data);
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} catch (e) {
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return callback(e);
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}
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callback();
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});
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}, err => {
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if (err) console.error(err.message);
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// configs is now a map of JSON data
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doSomethingWith(configs);
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});
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```
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```javascript
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var async = require("async");
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// ...or ES2017 async functions
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async.mapLimit(urls, 5, async function(url) {
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const response = await fetch(url)
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return response.body
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}, (err, results) => {
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if (err) throw err
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// results is now an array of the response bodies
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console.log(results)
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})
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```
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