Async concurrent iterator (async forEach)

Sindre Sorhus

Last update: Oct 21, 2022

Related tags

Control Flow each-async

Overview

each-async

Async concurrent iterator (async forEach)

Like async.each(), but tiny.

I often use async.each() for doing async operations when iterating, but I almost never use the other gadzillion methods in async.

Async iteration is one of the most used async control flow patterns.

I would strongly recommend using promises instead. You could then use the built-in Promise.all(), or p-map if you need concurrency control.

Install

$ npm install --save each-async

Usage

const eachAsync = require('each-async');

eachAsync(['foo','bar','baz'], (item, index, done) => {
	console.log(item, index);
	done();
}, error => {
	console.log('finished');
});
//=> 'foo 0'
//=> 'bar 1'
//=> 'baz 2'
//=> 'finished'

API

eachAsync(input, callback, [finishedCallback])

input

Type: Array

Array you want to iterate.

callback(item, index, done)

Type: Function

Called for each item in the array with the following arguments:

item: the current item in the array
index: the current index
done([error]): call this when you're done with an optional error. Supplying anything other than undefined/null will stop the iteration.

Note that order is not guaranteed since each item is handled concurrently.

finishedCallback(error)

Type: Function

Called when the iteration is finished or on the first error. First argument is the error passed from done() in the callback.

License

MIT © Sindre Sorhus

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Comments

Concurrency option

Just the same, but in series.

What do you think to add an extra param to do this action? like:

js
const concurrency = 1;

eachAsync(['foo','bar','baz'], concurrency, (item, index, done) => {
    console.log(item, index);
    done();
}, error => {
    console.log('finished');
}

enhancement help wanted

opened by Kikobeats 4

EJSONPARSE - @0.1.3

When i'm running the yeoman generator for angular i get the following error:

I've checked the package.json in the 0.1.3-tag, but everything seems to be ok.

opened by timoweiss 3
is necessary to ensure async iterator?

I want to know, if using this package, need to be sure that the iterator function that you put in the method need to be ensure async.

I really don't know if this is a problem about how internally async works or if is a JS/Node behaviour.

can you clarify this?

standalone async.ensureAsync => https://github.com/Kikobeats/ensure-async#ensure-async

opened by Kikobeats 2
fix test

Is this what you really wanted to do?

Also, I have a question: is this really a parallel-each? I mean, the next callback is called in order for every array element and since javascript is single threaded, every call will be executed sequentially and in order. The closest thing to a parallel execution that one could do (it's really just an async execution, anyway) is passing a callback that wraps all its content in a setTimeout so that the callbacks will be executed asynchronously (like you've done in the first test) but this is up to the user of the each-async, it's not done automatically by the utility. Am I right?

opened by redaemn 1