Pages with tag Asynchronous Programming

Asynchronous array operations in ES7 JavaScript async/await functions

A glaring problem with the most excellent async/await feature in JavaScript is all the existing coding structures that only work with synchronous code. In an async/await function it's trivially easy to write a simple "for" loop that contains whatever async/await calls you want. But as soon as you try "Array.forEach" with an async callback function it will fail miserably. That's because this function, like so many existing interfaces which take a callback function, assumes the callback is synchronous. Instead of waiting for the Promise to resolve, it plows on ahead executing the next iteration.
Avoid killing performance with asynchronous ES7 JavaScript async/await functions

While async functions in JavaScript are a gift from heaven, application performance can suffer if they're used badly. The straightforward approach in using async functions in some cases makes performance go down the drain. Some smart recoding can correct the problem, unfortunately at the cost of code clarity.  
Getting started with asynchronous read/write between Node.js 8 and MongoDB

Node.js and MongoDB work very well together, by marrying a JavaScript programming language with a JavaScript-oriented database engine. In this article we'll look at usage patterns for asynchronous coding in Node.js using async functions against the MongoDB database. Async functions are a powerful new feature in JavaScript, and we want to be sure to use them as widely as possible. Async functions gives cleaner database code because results plop into a convenient place.

How do function(err,data) callbacks work in Node? Those new to Node programming might find the callback function pattern a little difficult to understand.  For example how does the data get into the arguments to the function call, and how does the callback function get called?
Implementing worker queues for processing datasets in Node.js Processing large datasets can be done with a simple for loop. But, processing one data item at a time, eliminates possible efficiency gains from processing data in parallel. But, parallel processing is not scalable, since it can easily swamp CPU or memory resources. Worker queue packages help by constraining the number of parallel tasks executing at any one time.
New Book: Asynchronous JavaScript with Promises, Generators and async/await The JavaScript language is changing, and among the changes are three new features which will revolutionize the way we write asynchronous code in JavaScript. The problem with the old callback-oriented asynchronous coding practice is the Callback Hell resulting from stacking callbacks within callbacks within callbacks. Between Promises, Generators and the proposed async/await feature, JavaScript programmers can largely free themselves from Callback Hell, and write clean asynchronous code that's easier to write, easier to understand, easier to maintain, and more robust.
Node.js Script writers: Top-level async/await now available Async/await functions are a god-send to JavaScript programmers, simplifying writing asynchronous code. It turns difficult-to-write-and-debug pyramids of doom into clean clear code where the results and errors land in the natural place. It's been wonderful except for one thing, we could not use the await keyword in top-level code in Node.js. But, with Node.js 14.8 that's fixed.
Streamline Mocha/SuperTest REST tests with async functions

Mocha is an excellent unit testing framework for Node.js, and SuperTest is an excellent library for testing REST services. SuperTest is based on SuperAgent which makes it pretty darn easy to write code interfacing with a REST service. The problem with this combination is the test code can get pretty darn caught up in boilerplate callback functions, if you use Mocha and SuperTest the way its documented. Fortunately it's pretty easy to make SuperTest return a Promise, which then plays well with async functions, and Mocha is easily able to use an async function in a test scenario. So let's get started.
The advent of async/await for Node.js - Node.js v7 has now arrived

With today's first release of Node.js version 7, we now have async/await as a base feature of the platform. This is a significant milestone that wasn't even mentioned in the commit message. The async/await feature is so important that I'm preparing a short book to discuss JavaScript asynchronous programming patterns, that highly features async/await.

Troubles with Asynchronous code flows in JavaScript, and the async/await solution of ES-2017

Asynchronous coding is one of those powerful tools that can bite, if you're not careful. Passing around anonymous so-called "callback" functions is easy, and we do it all the time in JavaScript. Asynchronous callback functions are called, when needed, as needed, sometime in the future. The key result is that code execution is out-of-order with the order-of-appearance in the code.
Useful reading to understand the Promises, Generators and the async/await feature for Node.js/JavaScript

The long-awaited async/await feature for JavaScript promises to make our lives much easier. Instead of asynchronous JavaScript programming being tricky and error-prone, with async/await our code will look like regular synchronous code we write in other languages, but will accommodate asynchronous code execution while retaining the single-threaded nature of JavaScript. With this feature we declare async functions, and within their boundary magic occurs - we can put the "await" keyword in front of a function which produces a Promise, and automagically JavaScript will wait for the Promise to resolve and give us the result or else throw the error. What follows is a list of posts describing how to use async/await.