Articles Tagged JavaScript

Page reloads are a thing. Sometimes we refresh a page when we think it’s unresponsive, or believe that new content is available. Sometimes we’re just mad at the dang site and rage-refresh to let it know we’re displeased.

Wouldn’t be nice to know when a user refreshes the page? Not just that, but how many times? That data can help us trigger some sort of behavior after a certain number of reloads.

A sports site is a good example. If … Read article “One Way to Break Users Out of the Habit of Reloading Too Much”

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></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, have … Read article “What is super() in JavaScript?”

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. … Read article “Comparing the Different Types of Native JavaScript Popups”

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 ““Off The Main Thread””

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.… Read article “Model-Based Testing in React with State Machines”

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 there are fancy helper APIs. Sometimes there isn’t.… Read article “Working with Attributes on DOM Elements”

Date is weird in JavaScript. It gets on our nerves so much that we reach for libraries (like Date-fns and Moment) the moment (ha!) we need to work with date and time.

But we don’t always need to use libraries. Date can actually be quite simple if you know what to watch out for. In this article, I’ll walk you through everything you need to know about the Date object.… Read article “Everything You Need to Know About Date in JavaScript”

Sorting is a super handy JavaScript method that can display the values of an array in a certain order. Whether that’s real estate listings by price, burger joints by distance, or best nearby happy hours by rating, sorting arrays of information is a common need.

If you’re already doing this with JavaScript on a project, you are will likely using the built-in array .sort method, which is in the same family of array methods that includes .filter, .map and … Read article “Level up your .sort game”

JavaScript (or ECMAScript) is the programming language that powers the web. Created in May 1995 by Brendan Eich, it’s found its place as a widely-used and versatile technology. Despite its success, it’s been met with its fair share of criticism, especially for idiosyncrasies. Things like objects being casted to string form when used as indices, 1 == "1" returning true, or the notoriously confusing this keyword. A particularly interesting quirk though, is the existence of various techniques for variable privacy.… Read article “Implementing Private Variables In JavaScript”

Events are used to respond when a user clicks somewhere, focuses on a link with their keyboard, and changes the text in a form. When I first started learning JavaScript, I wrote complicated event listeners. More recently, I’ve learned how to reduce both the amount of code I write and the number of listeners I need.

Let’s start with a simple example: a few draggable boxes. We want to show the user which colored box they dragged.… Read article “The Thinking Behind Simplifying Event Handlers”