sg_asyncEach is like each, but async!

sg_asyncEach.demo.js

// //  //  //  //  //  //  //  //  //  //  //  //  //  //  //  //  //  //  // //

// works as a generic!
Array.sg_asyncEach([1, 2, 3],
	function(value, key, array) {
		console.log(value, key, array)
		return "eachFn result " + value
	},
	function(err, result) {
		console.log('sg_asyncEach callback', err && "Error!" || "Success!", result)
	}
)

// works as a method!
;[1, 2, 3].sg_asyncEach(
	function(value, key, array) {
		console.log(value, key, array)
		return "eachFn result " + value
	},
	function(err, result) {
		console.log('sg_asyncEach callback', err && "Error!" || "Success!", result)
	}
)

// error handling!
Array.sg_asyncEach([1, 2, 3]
	,function(){throw new Error("FAIL on purpose!")}
	,function(err){if (err) throw err}
)

// Works on objects and arrays!
Object.sg_asyncEach({a:'a', b:'b', c:'c'},
	function(value, key, array) {
		console.log(value, key, array)
		return "eachFn result " + value
	},
	function(err, result) {
		console.log('sg_asyncEach callback', err && "Error!" || "Success!", result)
	}
)

// //  //  //  //  //  //  //  //  //  //  //  //  //  //  //  //  //  //  // //

// Works on MooTools Elements collections if MooTools is in your environment!
if (typeof $$ != 'undefined'){

	new Element('div', {html:"<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol<p>Lol"})
	.inject(document.body)

	$$('p')
	.setStyle('color', '#f00')
	.sg_asyncEach(
		function(el, i, elements) {
			window.T = window.T || +new Date
			el.setStyle('color', '#0f0')
			return el
		},
		function(err, el) {
			el.appendText(' sg_asyncEach:' + (new Date - window.T) + 'ms')
		}
	)

}

sg_asyncEach.js

/*
---
name : sg_asyncEach
description : sg_asyncEach is like each, but async!

authors   : Thomas Aylott
copyright : © 2010 Thomas Aylott
license   : MIT

provides : [sg_asyncEach, Array.sg_asyncEach, Object.sg_asyncEach, Elements.sg_asyncEach]
...
*/

;(function(){

var call = Function.call

function sg_asyncEachItem
(	fn
,	value
,	key
,	object
,	callback
,	THIS
){
	if (THIS == null) THIS = this
	var result
	setTimeout(function(){
		try {
			result =
			call.call
			(	fn
			,	THIS
			,	value
			,	key
			,	object
			)
			callback(false, result, object)
		}
		catch (error){
			callback(error, result, object)
		}
	},
	0);
}


function Object_sg_asyncEach(object, fn, callback, THIS){
	for (var property in object)
	sg_asyncEachItem.call
	(	this
	,	fn
	,	object[property]
	,	property
	,	object
	,	callback
	,	THIS
	)
	return object
}

Object.sg_asyncEach = Object_sg_asyncEach


function Array_sg_asyncEach(array, fn, callback, THIS){
	for (var i = 0, l=array.length; i < l; ++i)
	sg_asyncEachItem.call
	(	this
	,	fn
	,	array[i]
	,	i
	,	array
	,	callback
	,	THIS
	)
	return array
}

Array.sg_asyncEach = Array_sg_asyncEach

Array.prototype.sg_asyncEach = function(fn, callback, THIS){
	return Array_sg_asyncEach.call(this, this, fn, callback, THIS)
}

if (Elements && Elements.implement)
	Elements.implement('sg_asyncEach', Array.prototype.sg_asyncEach)

}())

Demo: http://jsfiddle.net/Dvk7z/

I did an async invoke (it allows (a)sync) for benchmarkjs, waits for async testing to finish before going to the next benchmark and allows early exiting of the loop.
https://github.com/mathiasbynens/benchmark.js/blob/master/benchmark.js#L416-490

Not sure how handy setting the timeout to 0ms is though but async array methods are coo :D

Ahh, sweet, I'll check that out. Thanks!