All You Need to Know About async-each for Efficient Asynchronous Operations in JavaScript

Efficient handling of asynchronous operations is a core aspect of modern JavaScript development. The async-each library provides a simple yet robust solution for asynchronous iteration over collections. In this article, we’ll introduce async-each, explore its various APIs, and provide comprehensive examples to illustrate its usage.

What is async-each?

async-each is a small module for iterating arrays or objects asynchronously. It offers a pattern for performing parallel tasks with outstanding performance in many scenarios.

Installing async-each

npm install async-each --save

API Examples

each(array, iterator, callback)

Iterates over an array, applying an async function to each item in parallel.

  const each = require('async-each');
  
  each([1, 2, 3, 4], function (item, next) {
    console.log('Processing item: ' + item);
    setTimeout(next, 1000); // Simulate async work with setTimeout
  }, function (err) {
    if (err) throw err;
    console.log('All items processed successfully.');
  });

eachLimit(array, limit, iterator, callback)

Similar to each, but only a specific number of operations are executed in parallel.

  const eachLimit = require('async-each/limit');
  
  eachLimit([1, 2, 3, 4], 2, function (item, next) {
    console.log('Processing item: ' + item);
    setTimeout(next, 1000);
  }, function (err) {
    if (err) throw err;
    console.log('All items processed with limit.');
  });

eachSeries(array, iterator, callback)

Similar to each, but processes items in series, one at a time.

  const eachSeries = require('async-each/series');
  
  eachSeries([1, 2, 3, 4], function (item, next) {
    console.log('Processing item in series: ' + item);
    setTimeout(next, 1000);
  }, function (err) {
    if (err) throw err;
    console.log('All items processed in series.');
  });

Creating a Sample Application Using async-each

Let’s create a simple Node.js application that reads content from multiple files concurrently using async-each.

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

  const files = ['file1.txt', 'file2.txt', 'file3.txt'];

  each(files, function (file, next) {
    fs.readFile(file, 'utf8', function (err, content) {
      if (err) return next(err);
      console.log('Read content from: ' + file);
      next();
    });
  }, function (err) {
    if (err) console.error('An error occurred:', err);
    else console.log('Completed reading all files.');
  });

In this example, we use async-each to read contents from multiple files asynchronously and log their contents to the console. This illustrates a real-world scenario where async-each can streamline asynchronous tasks efficiently.

By incorporating async-each into your JavaScript applications, you can simplify the management of asynchronous operations, reduce complexity, and improve code readability.

For more information, visit the official async-each repository.

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