Introduction to asynckit

Asynckit is a powerful Node.js utility module designed to facilitate asynchronous programming. It offers a variety of useful APIs that help developers manage asynchronous workflows efficiently.

doSeries

The doSeries method allows you to process items in a series, ensuring that each item is processed before the next one begins.

const asynckit = require('asynckit');

const tasks = [1, 2, 3, 4, 5];

asynckit.serial(tasks, (item, callback) => {
   setTimeout(() => {
     console.log('Processing item:', item);
     callback(null, item * 2);
   }, 1000);
}, (err, results) => {
   if (err) {
     console.error('Error:', err);
   } else {
     console.log('Results:', results);
   }
});

doParallel

The doParallel method enables you to run multiple tasks in parallel, improving performance when tasks can execute concurrently.

const tasks = [1, 2, 3, 4, 5];

asynckit.parallel(tasks, (item, callback) => {
   setTimeout(() => {
     console.log('Processing item:', item);
     callback(null, item * 2);
   }, 1000);
}, (err, results) => {
   if (err) {
     console.error('Error:', err);
   } else {
     console.log('Results:', results);
   }
});

doLimit

The doLimit method allows you to control the concurrency by limiting the number of simultaneous operations.

const tasks = [1, 2, 3, 4, 5];

asynckit.limit(tasks, 2, (item, callback) => {
   setTimeout(() => {
     console.log('Processing item:', item);
     callback(null, item * 2);
   }, 1000);
}, (err, results) => {
   if (err) {
     console.error('Error:', err);
   } else {
     console.log('Results:', results);
   }
});

mapSeries

The mapSeries method processes an array of items one by one and maps them to a new array, preserving the order of the original array.

const items = [1, 2, 3, 4, 5];

asynckit.mapSeries(items, (item, callback) => {
   setTimeout(() => {
     callback(null, item * 2);
   }, 1000);
}, (err, results) => {
   if (err) {
     console.error('Error:', err);
   } else {
     console.log('Mapped Results:', results);
   }
});

mapParallel

The mapParallel method maps items to a new array by processing multiple items concurrently.

const items = [1, 2, 3, 4, 5];

asynckit.mapParallel(items, (item, callback) => {
   setTimeout(() => {
     callback(null, item * 2);
   }, 1000);
}, (err, results) => {
   if (err) {
     console.error('Error:', err);
   } else {
     console.log('Mapped Results:', results);
   }
});

Example Application

Let’s create an example application using asynckit to demonstrate the power of these APIs. Assume we have a list of URLs that we need to fetch and process:

const asynckit = require('asynckit');
const fetch = require('node-fetch');

const urls = [
   'https://api.example.com/data1',
   'https://api.example.com/data2',
   'https://api.example.com/data3',
];

asynckit.parallel(urls, (url, callback) => {
   fetch(url)
     .then(response => response.json())
     .then(data => callback(null, data))
     .catch(err => callback(err));
}, (err, results) => {
   if (err) {
     console.error('Error fetching data:', err);
   } else {
     console.log('Fetched data:', results);
   }
});

This application demonstrates how to asynchronously fetch data from multiple URLs in parallel using asynckit, providing an efficient solution for I/O-bound tasks.

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