What is super() in JavaScript?

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 and parent classes. If that’s totally new, you may want to start with Mozilla’s article on Object-oriented JavaScript for beginners.

Super isn’t unique to Javascript — many programming languages, including Java and Python, … Read article

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Comparing the Different Types of Native JavaScript Popups

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 you just passed. Here’s Firefox and Chrome:

Native popups in Firefox (left) and Chrome (right). Note the additional UI preventing additional dialogs in Firefox from triggering it more than once. You can… Read article

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“Off The Main Thread”

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 really busy doing them, then it’s not doing other things, like, say, handling our event handlers quickly.

There has been an interesting point/counter-point combo recently along … Read article

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Model-Based Testing in React with State Machines

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 is changed. We’ll learn how model-based testing can eliminate the need to manually write integration and end-to-end tests, by automatically generating full tests that keep up-to-date with an abstract model for any app.

From unit … Read article

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Working with Attributes on DOM Elements

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 you need to get them. Sometimes you get fancy helpers. Sometimes you don’t.

For this article, I’ll assume el is a DOM element in your JavaScript. Let’s say … Read article

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