index.js
function each(arr, callback) {
		var wrapper = this;
		if (this.isAsync) {
			return async.each(arr, function(item, cb) {
				wrapper.call(item, cb);
			}, callback);
		} else {
			arr.each(function(item) {
				wrapper.call(item);
			});
			if (callback) { callback(); }
		}
	}
function each(arr, callback) {
		var wrapper = this;
		if (this.isAsync) {
			return async.each(arr, function(item, cb) {
				wrapper.call(item, cb);
			}, callback);
		} else {
			arr.each(function(item) {
				wrapper.call(item);
			});
			if (callback) { callback(); }
		}
	}
Applies the function iterator to each item in arr, in parallel.

The context of the function will be the current item in the array.

@param  {Array} arr
@param  {Function} callback