foreachasync.js/README.md

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forEachAsync
===
Analogous to `[].forEach`, but handles items asynchronously with a final callback passed to `then`.
This is the most essential piece of the [`ArrayAsync`](https://github.com/FuturesJS/ArrayAsync) package.
For cases where you want to loop through batches of items at once (as opposed to strictly one-by-one as forEachAsync does), check out [`forAllAsync`](https://github.com/FuturesJS/forAllAsync) and [`lateral`](https://github.com/FuturesJS/lateral).
For cases where you want to loop through all items at once and we able to know when they're all done see [`join`](https://github.com/FuturesJS/join)
v5.x
----
We jumped from 3.x to 5.x because I'm considering creating a backwards-and-forwards compatible 4.x that
uses AngularJS-style function introspection to allow for having the next param.
Straight up, that's probably a bad idea and waste of time so I hope I don't actually do it.
Screencast
---
<http://youtu.be/O7egvEz4scA>
Usage
-----
```javascript
// EXAMPLE ASYNC FUNCTION
function getPicsAsync(animal) {
var flickerApi = "http://api.flickr.com/services/feeds/photos_public.gne?tagmode=any&format=json&tags=" + animal;
return requestAsync({ url: flickerApi });
}
```
```javascript
forEachAsync(['dogs', 'cats', 'octocats'], function (element) {
return getPicsAsync(element);
}).then(function () {
// then after all of the elements have been handled
// the final callback fires to let you know it's all done
console.log('All requests have finished');
});
```
### Supplying your own Promises Implementation
If native ES6 promises are not available, then you should supply your own Promises/A+
implementation like so:
```javascript
forEachAsync = forEachAsync.create(window.Promise || require('bluebird'));
```
Browser Installation
===
You can install from bower:
```bash
bower install --save forEachAsync@5.x
```
Or download the raw file from <https://raw.github.com/FuturesJS/forEachAsync/master/forEachAsync.js>:
```bash
wget https://raw.github.com/FuturesJS/forEachAsync/master/forEachAsync.js
```
```javascript
(function () {
'use strict';
var forEachAsync = window.forEachAsync
;
// do stuff ...
}());
```
**Note**: If you need both 3.x/4.x and 5.x version of `forEachAsync` in the browser... good luck with that...
Node Installation
===
```bash
npm install --save forEachAsync@5.x
```
API
===
**`forEachAsync(array, callback[, thisArg])`**
Parameters
* `array` Array of elements to iterate over
* `callback` Function to execute for each element, takes 4 arguments
* `element` a single element of the aforementioned array
* `index` the index of the current element
* `array` the same array mentioned above
* `thisArg` Object to use as `this` when executing `callback`
**`forEachAsync#then(done)`**
Parameters
* `then` is in the return value of `forEachAsync` and accepts a final `done` callback.
* `done` called after `forEachAsync` is complete, takes no arguments
Internal API
===
`forEachAsync.__BREAK`
This is used internally for the purposes of the `ArrayAsync` library.
Please don't `break` stuff; use [`ArrayAsync`](https://github.com/FuturesJS/ArrayAsync)`.someAsync` or [`ArrayAsync`](https://github.com/FuturesJS/ArrayAsync)`.everyAsync` instead.