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JavaScript ~~

9.12.2019
JavaScript is loaded with tiny syntax tricks to accomplish useful effects. For example, explore any codebase to see !! being used to convert a value to a boolean value. Have you seen ~~ before? Let’s have a look at what it does! We can employ ~~ to trigger a Math.floor operation with those...

Build your own React

20.11.2019
Wowza! Rodrigo Pombo’s article about how to build React from scratch is fantastic, not only because it’s well written, but because of the outstanding interaction design: each line in the code examples ge highlighted and explored in further detail as you scroll down the page. This makes it super...

React Hooks, které potřebujete znát

12.11.2019
React s verzí 16.8 přináší zásadní novinku, a tou jsou Hooks, které mají přinést řešení pro hned 3 největší problémy, se kterými se v Reactu potýkáme. Implementace komponent pomocí tříd, sdílení logiky, nepraktický způsob práce s životním cyklem komponent. Představíme vám React Hooks a na konci...

What is super() in JavaScript?

6.11.2019
What's happening when you see some JavaScript that calls super()?.In a child class, you use super() to call its parent’s constructor and super.<methodName> to access its parent’s methods. This article will assume at least a little familiarity with the concepts of constructors and child...

JavaScript waitForTime

6.11.2019
I write a lot of tests for new features within Firefox DevTools. We have hundreds of “mochitests” which open the browser and perform synthetic actions like clicking, typing, and other user actions. I’ve previously written about waitForever which essentially halts following actions...

Comparing the Different Types of Native JavaScript Popups

31.10.2019
JavaScript has a variety of built-in popup APIs that display special UI for user interaction. Famously: alert("Hello, World!"); The UI for this varies from browser to browser, but generally you’ll see a little window pop up front and center in a very show-stopping way that contains the message...

How to Create a QR Code

15.10.2019
QR codes aren’t everyone’s cup of tea but I quite like them. If I see something I want to remember or check out later, especially when on the road, it’s super easy to take a quick picture — it’s much easier than trying to remember a URL and much faster than typing...

Jaká byla Nordic.js 2019

14.10.2019
Série evropských JavaScriptových konferencí JSConf zaznamenala letos výraznou změnu, když její hlavní a zakládající berlínská odnož oznámila ukončení svého působení. Tíha zodpovědnosti se tak přesouvá na ostatní regionální organizátory

How to Detect an Ad Blocker

8.10.2019
One of the unspoken rules of the internet is that most content is “free”… at the cost of webpage being littered with advertisements and trackers. This was’t a big problem in the early internet days but trackers and advertisements have become so intrusive and unapologetically...

designMode

1.10.2019
Every once in a while I stumble upon an API or browser setting that I can’t believe ever existed. Such examples can be seen in the numerous String.prototype properties such as bold, italics, and even blink, which wrap given string text in their representative HTML tags. Bizarre. It...

“Off The Main Thread”

10.9.2019
JavaScript is what they call "single-threaded." As Brian Barbour puts it: This means it has one call stack and one memory heap. We all feel a symptom of that regularly in the form of performance jank and non-interactivity on elements or entire sites. If we give JavaScript lots of jobs and it gets...

How to Not Minify Source with webpack

10.9.2019
The webpack JavaScript utility has taken over the modern JavaScript landscape, so much so that it’s hard to be a JavaScript developer and not use it. JavaScript build utilities are the point where they do best practices implicitly, like minify code, caching, and more. I was recently debugging...

Stop Installing Packages Globally

9.9.2019
These days, most front-end projects are going to involve NPM packages of some kind. Occasionally, when browsing documentation for these packages, I’ll see a recommendation to install a package like this. yarn global add <package> Or like this. npm install --global <package> In both...

Model-Based Testing in React with State Machines

4.9.2019
Testing applications is crucially important to ensuring that the code is error-free and the logic requirements are met. However, writing tests manually is tedious and prone to human bias and error. Furthermore, maintenance can be a nightmare, especially when features are added or business logic...

Working with Attributes on DOM Elements

30.8.2019
The DOM is just a little weird about some things, and the way you deal with attributes is no exception. There are a number of ways to deal with the attributes on elements. By attributes, I mean things like the id in <div id="cool"></div>. Sometimes you need to set them. Sometimes...

Promises and Static Values

23.8.2019
Async can throw a real wrench into the cogs of our programming workflows, all despite the fact that async is the modern JavaScript pattern. While async/await helps, there’s sometimes confusion about the way to have a single function that returns a value whether it exists or needs a Promise...

then on Objects

5.8.2019
Promises were a revelation in JavaScript development, allowing us to enjoy async processing and avoid callback hell. Many new APIs like Battery API, Cache API, and others use the promise API. One fact you may not know is that you can add a then method to any object to make it Promise-like!...

Optional Chaining

29.7.2019
For all of the improvements that the JavaScript language has added over the past few years, like the spread operator, default argument values, and arrow functions, there are still a few features I’d love to see implemented. On such feature is optional chaining. Optional chaining allows...

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