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forEachAsync

| Sponsored by ppl

Analogous to [].forEach, but handles items asynchronously with a final callback passed to then.

This is the most essential piece of the 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 and 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

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

https://youtu.be/O7egvEz4scA

Usage

  // 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 });
  }

  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:

  forEachAsync = forEachAsync.create(window.Promise || require('bluebird'));

Browser Installation

You can install from bower:

bower install --save forEachAsync@5.x

Or download the raw file from https://git.coolaj86.com/coolaj86/foreachasync.js/raw/branch/master/foreachasync.js:

wget https://git.coolaj86.com/coolaj86/foreachasync.js/raw/branch/master/foreachasync.js

(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

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.someAsync or ArrayAsync.everyAsync instead.

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