for-each-async

ForEachAsync 
===========

Asynchronous Array.forEach. The [forEach()][external_mdn_foreach] method executes a provided function once per array element.

*

$3

``bash
$ npm install for-each-async
`

$3

`
forEachAsync(array, iteratee, done[, thisArg])
`

Parameters

array Array* - The array to iterate through.

iteratee Function* - The function to execute on each value in the array, taking four arguments:
val Any* - The current element being processed in the array.

n Integer* - The index of the current element being processed in the array.

arr Array* - The array forEachAsync was called upon.

next Function* - The function to call when you are ready to advance to the next element in the array.

done Function* - The function called when the loop has finished.

thisArg Object* (Optional) - Value to use as this when executing callback.

[More information][external_mdn_foreach] on how forEach works.

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* Asynchronously print the contents of an array.

The following code logs a line for each element in an array:

`js
function logArrayElements(val, n, arr, next) {
console.log('a[' + n + '] = ' + val);
next();
}

// Notice that index 2 is skipped since there is no item at
// that position in the array.
forEachAsync([2, 5, , 9], logArrayElements, () => {
console.log('done');
});
// logs:
// a[0] = 2
// a[1] = 5
// a[3] = 9
// done
`

* Asynchronously using thisArg

The following (contrived) example updates an object's properties from each entry in the array:

`js
function Counter() {
this.sum = 0;
this.count = 0;
}

Counter.prototype.add = function (array) {
forEachAsync(array, function (val, n, arr, next) {
this.sum += entry;
++this.count;
next();
}, function () {
// Done
}, this);
// ^---- Note
};

var obj = new Counter();
obj.add([2, 5, 9]);
obj.count
// 3
obj.sum
// 16
`

Since the thisArg parameter (this) is provided to forEachAsync(), it is passed to callback each time it's invoked, for use as its this` value.

*

Authors
-------
* [Nathan Buchar]

License
-------
ISC

[external_mdn_foreach]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach

[Nathan Buchar]: mailto:hello@nathanbuchar.com