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+![Async Logo](https://raw.githubusercontent.com/caolan/async/master/logo/async-logo_readme.jpg)
+
+[![Build Status via Travis CI](https://travis-ci.org/caolan/async.svg?branch=master)](https://travis-ci.org/caolan/async)
+[![NPM version](https://img.shields.io/npm/v/async.svg)](https://www.npmjs.com/package/async)
+[![Coverage Status](https://coveralls.io/repos/caolan/async/badge.svg?branch=master)](https://coveralls.io/r/caolan/async?branch=master)
+[![Join the chat at https://gitter.im/caolan/async](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/caolan/async?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+
+*For Async v1.5.x documentation, go [HERE](https://github.com/caolan/async/blob/v1.5.2/README.md)*
+
+Async is a utility module which provides straight-forward, powerful functions
+for working with asynchronous JavaScript. Although originally designed for
+use with [Node.js](https://nodejs.org/) and installable via `npm install --save async`,
+it can also be used directly in the browser.
+
+Async is also installable via:
+
+- [bower](http://bower.io/): `bower install async`
+- [component](https://github.com/componentjs/component): `component install caolan/async`
+- [jam](http://jamjs.org/): `jam install async`
+
+Async provides around 70 functions that include the usual 'functional'
+suspects (`map`, `reduce`, `filter`, `each`…) as well as some common patterns
+for asynchronous control flow (`parallel`, `series`, `waterfall`…). All these
+functions assume you follow the Node.js convention of providing a single
+callback as the last argument of your asynchronous function -- a callback which expects an Error as its first argument -- and calling the callback once.
+
+
+## Quick Examples
+
+```js
+async.map(['file1','file2','file3'], fs.stat, function(err, results){
+ // results is now an array of stats for each file
+});
+
+async.filter(['file1','file2','file3'], function(filePath, callback) {
+ fs.access(filePath, function(err) {
+ callback(null, !err)
+ });
+}, function(err, results){
+ // results now equals an array of the existing files
+});
+
+async.parallel([
+ function(callback){ ... },
+ function(callback){ ... }
+], function(err, results) {
+ // optional callback
+};
+
+async.series([
+ function(callback){ ... },
+ function(callback){ ... }
+]);
+```
+
+There are many more functions available so take a look at the docs below for a
+full list. This module aims to be comprehensive, so if you feel anything is
+missing please create a GitHub issue for it.
+
+## Common Pitfalls [(StackOverflow)](http://stackoverflow.com/questions/tagged/async.js)
+
+### Synchronous iteration functions
+
+If you get an error like `RangeError: Maximum call stack size exceeded.` or other stack overflow issues when using async, you are likely using a synchronous iteratee. By *synchronous* we mean a function that calls its callback on the same tick in the javascript event loop, without doing any I/O or using any timers. Calling many callbacks iteratively will quickly overflow the stack. If you run into this issue, just defer your callback with `async.setImmediate` to start a new call stack on the next tick of the event loop.
+
+This can also arise by accident if you callback early in certain cases:
+
+```js
+async.eachSeries(hugeArray, function iteratee(item, callback) {
+ if (inCache(item)) {
+ callback(null, cache[item]); // if many items are cached, you'll overflow
+ } else {
+ doSomeIO(item, callback);
+ }
+}, function done() {
+ //...
+});
+```
+
+Just change it to:
+
+```js
+async.eachSeries(hugeArray, function iteratee(item, callback) {
+ if (inCache(item)) {
+ async.setImmediate(function () {
+ callback(null, cache[item]);
+ });
+ } else {
+ doSomeIO(item, callback);
+ //...
+ }
+});
+```
+
+Async does not guard against synchronous iteratees for performance reasons. If you are still running into stack overflows, you can defer as suggested above, or wrap functions with [`async.ensureAsync`](#ensureAsync) Functions that are asynchronous by their nature do not have this problem and don't need the extra callback deferral.
+
+If JavaScript's event loop is still a bit nebulous, check out [this article](http://blog.carbonfive.com/2013/10/27/the-javascript-event-loop-explained/) or [this talk](http://2014.jsconf.eu/speakers/philip-roberts-what-the-heck-is-the-event-loop-anyway.html) for more detailed information about how it works.
+
+
+### Multiple callbacks
+
+Make sure to always `return` when calling a callback early, otherwise you will cause multiple callbacks and unpredictable behavior in many cases.
+
+```js
+async.waterfall([
+ function (callback) {
+ getSomething(options, function (err, result) {
+ if (err) {
+ callback(new Error("failed getting something:" + err.message));
+ // we should return here
+ }
+ // since we did not return, this callback still will be called and
+ // `processData` will be called twice
+ callback(null, result);
+ });
+ },
+ processData
+], done)
+```
+
+It is always good practice to `return callback(err, result)` whenever a callback call is not the last statement of a function.
+
+
+### Binding a context to an iteratee
+
+This section is really about `bind`, not about `async`. If you are wondering how to
+make `async` execute your iteratees in a given context, or are confused as to why
+a method of another library isn't working as an iteratee, study this example:
+
+```js
+// Here is a simple object with an (unnecessarily roundabout) squaring method
+var AsyncSquaringLibrary = {
+ squareExponent: 2,
+ square: function(number, callback){
+ var result = Math.pow(number, this.squareExponent);
+ setTimeout(function(){
+ callback(null, result);
+ }, 200);
+ }
+};
+
+async.map([1, 2, 3], AsyncSquaringLibrary.square, function(err, result){
+ // result is [NaN, NaN, NaN]
+ // This fails because the `this.squareExponent` expression in the square
+ // function is not evaluated in the context of AsyncSquaringLibrary, and is
+ // therefore undefined.
+});
+
+async.map([1, 2, 3], AsyncSquaringLibrary.square.bind(AsyncSquaringLibrary), function(err, result){
+ // result is [1, 4, 9]
+ // With the help of bind we can attach a context to the iteratee before
+ // passing it to async. Now the square function will be executed in its
+ // 'home' AsyncSquaringLibrary context and the value of `this.squareExponent`
+ // will be as expected.
+});
+```
+
+## Download
+
+The source is available for download from
+[GitHub](https://raw.githubusercontent.com/caolan/async/master/dist/async.min.js).
+Alternatively, you can install using npm:
+
+```bash
+$ npm install --save async
+```
+
+As well as using Bower:
+
+```bash
+$ bower install async
+```
+
+You can then `require()` async as normal:
+
+```js
+var async = require("async");
+```
+
+Or require individual methods:
+
+```js
+var waterfall = require("async/waterfall");
+var map = require("async/map");
+```
+
+__Development:__ [async.js](https://raw.githubusercontent.com/caolan/async/master/dist/async.js) - 29.6kb Uncompressed
+
+### In the Browser
+
+Async should work in any ES5 environment (IE9 and above).
+
+Usage:
+
+```html
+<script type="text/javascript" src="async.js"></script>
+<script type="text/javascript">
+
+ async.map(data, asyncProcess, function(err, results){
+ alert(results);
+ });
+
+</script>
+```
+
+### ES Modules
+
+We also provide async as a collection of ES2015 modules, in an alternative `async-es` package on npm.
+
+```bash
+$ npm install --save async-es
+```
+
+```js
+import waterfall from 'async-es/waterfall';
+import async from 'async-es';
+```
+