Skip to main content

Tagged “javascript”

Tabs: truth, fiction and practical measures

My colleague Anda and I just had a good conversation about tabs, and specifically the company’s tabs component. I’ve mentioned before that our tabs are unconventional and potentially confusing, and Anda was interested to hear more.

Editable table cells

Yesterday the Design System team received a tentative enquiry regarding making table cells editable. I’m not yet sure whether or not this is a good idea – experience and spidey sense tell me it’s not – but regardless I decided to start exploring so as to base my answer on facts and avoid being overly cautious.

How we think about browsers, on GitHub’s blog

Keith Cirkel of Github has written about how they think about browsers and it’s interesting. In summary Github achieve:

  • improved performance;
  • exploiting new native technologies; and
  • universal user access/inclusion

…via a progressive enhancement strategy that ensures a basic experience for all but delivers an enhanced experience to most. Their tooling gets a bit deep/exotic in places but I think the basic premise is:

  1. decide on what our basic experience is, then use native HTML combined with a bare minimum of other stuff to help old browsers deliver that; and
  2. exploit new JS features in our enhanced experience (the one most people will get) to make it super lean and fast

Pretty cool.

Refactoring a modal dialogue in 2022

My team will soon be refactoring our modal dialogue component. Ours has a few deficiencies, needs better developer experience and documentation, is not built to our Design System component standards, and could use a resilience boost from some progressive enhancement.

My first Web Component: a disclosure widget

After a couple of years of reading about web components (and a lot of head-scratching), I’ve finally got around to properly creating one… or at least a rough first draft!

Building a toast component (by Adam Argyle)

Great tutorial (with accompanying video) from Adam Argyle which starts with a useful definition of what a Toast is and is not:

Toasts are non-interactive, passive, and asynchronous short messages for users. Generally they are used as an interface feedback pattern for informing the user about the results of an action. Toasts are unlike notifications, alerts and prompts because they're not interactive; they're not meant to be dismissed or persist. Notifications are for more important information, synchronous messaging that requires interaction, or system level messages (as opposed to page level). Toasts are more passive than other notice strategies.

Web animation tips

Warning: this entry is a work-in-progress and incomplete. That said, it's still a useful reference to me which is why I've published it. I’ll flesh it out soon!

There are lots of different strands of web development. You try your best to be good at all of them, but there’s only so much time in the day! Animation is an area where I know a little but would love to know more, and from a practical perspective I’d certainly benefit from having some road-ready solutions to common challenges. As ever I want to favour web standards over libraries where possible, and take an approach that’s lean, accessible, progressively-enhanced and performance-optimised.

Here’s my attempt to break down web animation into bite-sized chunks for ocassional users like myself.

Front-end architecture for a new website (in 2021)

Just taking a moment for some musings on which way the front-end wind is blowing (from my perspective at least) and how that might practically impact my approach on the next small-ish website that I code.

Resources for learning front-end web development

A designer colleague recently asked me what course or resources I would recommend for learning front-end web development. She mentioned React at the beginning but I suggested that it’d be better to start by learning HTML, CSS, and JavaScript. As for React: it’s a subset or offshoot of JavaScript so it makes sense to understand vanilla JS first.

For future reference, here are my tips.

Collapsible sections, on Inclusive Components

It’s a few years old now, but this tutorial from Heydon Pickering on how to create an accessible, progressively enhanced user interface comprised of multiple collapsible and expandable sections is fantastic. It covers using the appropriate HTML elements (buttons) and ARIA attributes, how best to handle icons (minimal inline SVG), turning it into a web component and plenty more besides.

Buttons and links: definitions, differences and tips

Some of the web’s design and development practices have led to buttons and links becoming conceptually bundled together and misunderstood. Practitioners can fall into the trap of seeing the surface-level commonality that “you click the thing, then something happens” and mistakenly thinking the two elements are interchangeable. Some might even consider them as a single “button component” without considering the distinctions underneath. However this mentality causes our users problems and is harmful for effective web development. In this post I’ll address why buttons and links are different and exist separately, and when to use each.

HTML with Superpowers (from Dave Rupert)

Here’s a great new presentation by Dave Rupert (of the Shop Talk show) in which he makes a compelling case for adopting Web Components. Not only do they provide the same benefits of encapsulation and reusability as components in proprietary JavaScript frameworks, but they also bring the reliability and portability of web standards, work without build tools, are suited to progressive enhancement, and may pave the way for a better web.

How to debug event listeners with your browser’s developer tools (on Go Make Things)

On the page, right-click the element you want to debug event listeners for, then click Inspect Element. In chromium-based browsers like MS Edge and Google Chrome, click the Event Listeners tab in Developer Tools. There, you’ll see a list of all of the events being listened to on that element. If you expand the event, you can see what element they’re attached to and click a link to open up the actual event listener itself in the JavaScript.

Testing ES modules with Jest

Here are a few troubleshooting tips to enable Jest, the JavaScript testing framework, to be able to work with ES modules without needing Babel in the mix for transpilation. Let’s get going with a basic set-up.

Harry Roberts says “Get Your Head Straight”

Harry Roberts (who created ITCSS for organising CSS at scale but these days focuses on performance) has just given a presentation about the importance of getting the content, order and optimisation of the <head> element right, including lots of measurement data to back up his claims. Check out the slides: Get your Head Straight

Practical front-end performance tips

I’ve been really interested in the subject of Web Performance since I read Steve Souders’ book High Performance Websites back in 2007. Although some of the principles in that book are still relevant, it’s also fair to say that a lot has changed since then so I decided to pull together some current tips. Disclaimer: This is a living document which I’ll expand over time. Also: I’m a performance enthusiast but not an expert. If I have anything wrong, please let me know.

Progressively enhanced burger menu tutorial by Andy Bell

Here’s a smart and comprehensive tutorial from Andy Bell on how to create a progressively enhanced narrow-screen navigation solution using a custom element. Andy also uses Proxy for “enabled” and “open” state management, ResizeObserver on the custom element’s containing header for a Container Query like solution, and puts some serious effort into accessible focus management.


Astro looks very interesting. It’s in part a static site builder (a bit like Eleventy) but it also comes with a modern (revolutionary?) developer experience which lets you author components as web components or in a JS framework of your choice but then renders those to static HTML for optimal performance. Oh, and as far as I can tell theres no build pipeline!

Astro lets you use any framework you want (or none at all). And if most sites only have islands of interactivity, shouldn’t our tools optimize for that?


Lean, hackable, extensible slide deck framework

I’ve been on the lookout for a lightweight, web standards based slide deck solution for a while and this one from Lea Verou could well be perfect.

Container Queries in Web Components | Max Böck

Max’s demo is really clever and features lots of interesting web component related techniques.

I came up with this demo of a book store. Each of the books is draggable and can be moved to one of three sections, with varying available space. Depending on where it is placed, different styles will be applied to the book.

Ruthlessly eliminating layout shift on, by Zach Leatherman

I love hearing about clever front-end solutions which combine technologies and achieve multiple goals. In Zach’s post we hear how Netlify’s website suffered from layout shift when conditionally rendering dismissible promo banners, and how he addressed this by rethinking the problem and shifting responsibilities around the stack.

Here’s my summary of the smart ideas covered in the post:

  • decide on the appropriate server-rendered content… in this case showing rather than hiding the banner, making the most common use case faster to load
  • have the banner “dismiss” button’s event handling script store the banner’s href in the user’s localStorage as an identifier accessible on return visits
  • process lightweight but critical JavaScript logic early in the <head>… in this case a check for this banner’s identifier existing in localStorage
  • under certain conditions – in this case when the banner was previously seen and dismissed – set a “state” class (banner--hide) on the <html> element, leading to the component being hidden seamlessly by CSS
  • build the banner as a web component, the first layer of which being a custom element <announcement-banner> and the second a JavaScript class to enhance it
  • delegate responsibility for presenting the banner’s “dismiss” button to the same script responsible for the component’s enhancements, meaning that a broken button won’t be presented if that script were to break.

So much to like in there!

Here are some further thoughts the article provoked.

Web components FTW

It feels like creating a component such as this one as a web component leads to a real convergence of benefits:

  • tool-free, async loading of the component JS as an ES module
  • fast, native element discovery (no need for a document.querySelector)
  • enforces using a nice, idiomatic class providing encapsulation and high-performing native callbacks
  • resilience and progressive enhancement by putting all your JS-dependent stuff into the JS class and having that enhance your basic custom element. If that JS breaks, you still have the basic element and won’t present any broken elements.

Even better, you end up with framework-independent, standards-based component that you could share with others for reuse elsewhere, just like Zach did.

Multiple banners

I could see there being a case where there are multiple banners during the same time period. I guess in that situation the localStorage banner value could be a stringified object rather than a simple, single-URL string.

Setting context on the root

It’s really handy to have a way to exert just-in-time control over the display of a server-rendered element in a way that avoids flashes of content… and adding a class to the <html> element offers that. In this approach, we run the small amount of JavaScript required to test a local condition (e.g. checking for a value in localStorage) really early. That lets us process our conditional logic before the element is rendered… although this also means that it’s not yet available in the DOM for direct manipulation. But adding a class to the HTML element means that we can pre-prepare CSS to use that class as a contextual selector for hiding the element.

We’re already familiar with the technique of placing classes on the root element from libraries like modernizr and some font-loading approaches, but this article serves as a reminder that we can employ it whenever we need it.

Handling the close button

Zach’s approach to handling the banner’s dismiss button was interesting. He makes sure that it’s not shown unless the web component’s JavaScript runs successfully which is great, but rather than inject it with JavaScript he includes it in the initial HTML but hidden with CSS, and his method of hiding is opacity.

We use opacity to toggle the close button so that it doesn’t reflow the component when it’s enabled via JavaScript.

I think what Zach’s saying is that the alternatives – inserting the button with JS, or toggling the hidden attribute or its CSS counterpart display:none – would affect geometry causing the browser to perform layout… whereas modifying opacity does not.

I love that level of diligence! Typically I prefer to delegate responsibility for inserting JS-dependent buttons to JavaScript because in comparison to including a button in the server-rendered HTML then hiding it, it feels more resilient and a more maintainable separation of concerns. However as always the best solution depends on the situation.

If I were going down Zach’s route I think I’d replace opacity with visibility since the latter hiding method removes the hidden element from the document which feels more accessible, while still avoiding triggering the reflow that display would.


In a server-side scripted application – one using Rails or PHP, for example – you could alternatively handle persisting state with cookies rather than localStorage… allowing you to test for the presence of the cookie on the server then handle conditional rendering of the banner on the server too, rather than needing classes which trigger hiding. I can see an argument for that. Thing is though, not everyone’s working in that environment. Zach has provided a standalone solution.


Observer APIs in a nutshell

I’ve played with the various HTML5 Observer APIs (IntersectionObserver, ResizeObserver and MutationObserver) a little over the last few years—for example using ResizeObserver in a container query solution for responsive grids. But in all honesty their roles, abilities and differences haven’t yet fully stuck in my brain. So I’ve put together a brief explainer for future reference.

Front-of-the-front-end and back-of-the-front-end web development (by Brad Frost)

The Great Divide between so-called front-end developers is real! Here, Brad Frost proposes some modern role definitions.

A front-of-the-front-end developer is a web developer who specializes in writing HTML, CSS, and presentational JavaScript code.

A back-of-the-front-end developer is a web developer who specializes in writing JavaScript code necessary to make a web application function properly.

Vanilla JS List

Here’s Chris Ferdinandi’s curated list of organisations which use vanilla JS to build websites and web apps.

You don’t need a heavyweight JavaScript framework, and vanilla JS does scale.

Accessible interactions (on Adactio)

Jeremy Keith takes us through his thought process regarding the choice of link or button when planning accessible interactive disclosure elements.

Progressively enhanced JavaScript In Real Life

Over the last couple of days I’ve witnessed a good example of progressive enhancement “In Real Life”. And I think it’s good to log and share these validations of web development best practices when they happen so that their benefits can be seen as real rather than theoretical.

Newsletters, by Robin Rendle

A fantastic so-called “Scroll Story” from Robin Rendle. In his own words it’s “an elaborate blog post where I rant about a thing” however given the beautiful typography, layout and illustrations on show I think he’s selling it a little short!

Browser Support Heuristics

In web development it’s useful when we can say “if the browser supports X, then we know it also supports Y”.

Minimalist Container Queries

Scott Jehl’s experimental take on a container/element query aimed at letting us set responsive styles for our elements based on their immediate context rather than that of the viewport.

I made a quick and minimal take on approximating Container/Element Queries using a web component and basic CSS selectors.

Sets in JavaScript

I don’t often store things in a Set in JavaScript, but maybe I should. The fact it will only store unique values makes it pretty handy.

Cheating Entropy with Native Web Technologies (on Jim Nielsen’s Weblog)

This is why, over years of building for the web, I have learned that I can significantly cut down on the entropy my future self will have to face by authoring web projects in vanilla HTML, CSS, and JS. I like to ask myself questions like:

  • Could this be done with native ES modules instead of using a bundler?
  • Could I do this with DOM scripting instead of using a JS framework?
  • Could I author this in CSS instead of choosing a preprocessor?

Introducing Rome

We’re excited to announce the first beta release and general availability of the Rome linter for JavaScript and TypeScript. This is the beginning of an entire suite of tools. Rome is not only a linter, but also a compiler, bundler, test runner, and more, for JavaScript, TypeScript, HTML, JSON, Markdown, and CSS. We aim to unify the entire frontend development toolchain.

Three CSS Alternatives to JavaScript Navigation (on CSS-Tricks)

In general this is a decent article on non-JavaScript-based mobile navigation options, but what I found most interesting is the idea of having a separate page for your navigation menu (at the URL /menu, for example).

Who said navigation has to be in the header of every page? If your front end is extremely lightweight or if you have a long list of menu items to display in your navigation, the most practical method might be to create a separate page to list them all.

Color Theme Switcher (on

Max shows us how to build a colour theme switcher to let users customise your website. He uses a combination of Eleventy, JSON, Nunjucks with macros, a data attribute on the html element, CSS custom properties and a JavaScript based switcher.

Debouncing vs. throttling with vanilla JS (on Go Make Things)

Chris explains how debouncing and throttling are two related but different techniques for improving performance and user experience when working with frequently invoked JavaScript event handlers.

With throttling, you run a function immediately, then wait a specified amount of time before running it again. Any additional attempts to run it before that time period is over are ignored.

With debouncing, after the relevant event fires a specified time period must pass uninterrupted in order for your function to run. When the time period has passed uninterrupted, that last attempt to run the function is the one that runs, with any previous attempts ignored.

Striking a Balance Between Native and Custom Select Elements (on CSS-Tricks)

We’re not going to try to replicate everything that the browser does by default with a native select element. We’re going to literally use a select element when any assistive tech is used. But when a mouse is being used, we’ll show the styled version and make it function as a select element.

JavaScript Arrow Functions

JavaScript arrow functions are one of those bits of syntax about which I occasionally have a brain freeze. Here’s a quick refresher for those moments.

We’ve ruined the Web. Here’s how we fix it. (This is HCD podcast)

During the COVID situation, people have an urgent need to access critical information online. But in 2020, the average webpage is rammed full of large JavaScript files, huge images etc, and as a result is slow to load. This problem is likely to be most keenly felt by those who don’t have the luxury of fast internet – potentially the same people who need access to that critical information the most.

Here’s a brilliant discussion between Gerry McGovern and Jeremy Keith on that problem, suggesting tactics to help fix things such as performance budgets, introducing tactics at the design stage to mimic slow connections and other access constraints, optimising for return visits, progressive enhancement and more.

I have to reluctanctly agree on this one. I’ve interviewed quite a few candidates for “front-end developer” (or similarly named) positions over recent years and the recurring pattern is that they are strong on JavaScript (though not necessarily the right time to use it) and weak on HTML, CSS and the “bigger picture”.

Multiplayer Crosswords (

I wanted there to be an easy way to complete crosswords together that didn’t need people to pass a phone back and forth or for a copy of the crossword to be made in a shared Google Spreadsheet.

In the same vein as Jeremy Keith’s recent blog post, Hydration, which calls out some of the performance and user experience problems associated with current Server Side Rendering approaches, I think Jake Archibald is absolutely bang on the money here.

BBC GEL Inclusive Components Technical Guide

The BBC Global Experience Language (GEL) Technical Guides are a series of framework-agnostic, code-centric recommendations and examples for building GEL design patterns in websites. They illustrate how to create websites that comply with all BBC guidelines and industry best practice, giving special emphasis to accessibility.

You Don't Need

A nice list of tips and tools on how to use simpler browser standards and APIs to avoid the added weight of unnecessary JavaScript and libraries.

Hydration (Adactio: Journal)

The situation we have now is the worst of both worlds: server-side rendering followed by a tsunami of hydration. It has a whiff of progressive enhancement to it (because there’s a cosmetic separation of concerns) but it has none of the user benefits.

Testing Stimulus Controllers

Stimulus JS is great but doesn’t provide any documentation for testing controllers, so here’s some of my own that I’ve picked up.

Required 3rd-party libraries

Basic Test

// hello_controller.test.js
import { Application as StimulusApp } from "stimulus";
import HelloController from "path/to/js/hello_controller";

describe("HelloController", () => {
beforeEach(() => {
// Insert the HTML and register the controller
document.body.innerHTML = `
<div data-controller="hello">
<input data-target="" type="text">
<button data-action="click->hello#greet">
<span data-target="hello.output">
StimulusApp.start().register('hello', HelloController);

it("inserts a greeting using the name given", () => {
const helloOutput = document.querySelector("[data-target='hello.output']");
const nameInput = document.querySelector("[data-target='']");
const greetButton = document.querySelector("button");
// Change the input value and click the greet button
nameInput.value = "Laurence";;
// Check we have the correct greeting
expect(helloOutput).toHaveTextContent("Hello, Laurence!");

When should you add the defer attribute to the script element? (on Go Make Things)

For many years I’ve placed script elements just before the closing body tag rather than in the <head>. Since a standard <script> element is render-blocking, the theory is that by putting it at the end of the document – after the main content of the page has loaded – it’s no longer blocking anything, and there’s no need to wrap it in a DOMContentLoaded event listener.

It turns out that my time-honoured default is OK, but there is a better approach.

Async and Await

My notes and reminders for handling promises with async and await In Real Life.

Modest JS Works

Pascal Laliberté has written a short, free, web-based book which advocates a modest and layered approach to using JavaScript.

I make the case for The JS Gradient, a principle whereby your app can have multiple coexisting modern JS approaches, starting from the global sprinkles to spot view-models to, yes, an SPA if that’s really necessary. At each point in the gradient, you’ll see when it’s a good idea to go a step further toward heavier JavaScript, or not.

How to manage JavaScript dependencies

Managing JavaScript dependencies is about as much fun as a poke in the eye. However even if—like me—you prefer to keep things lean and dependency-free as far as possible, it’s something you’re going to need to do either in large work projects or as your personal side-project grows. In this post I tackle it head-on to reduce the problem to some simple concepts and practical techniques.

Webfont loading strategies

When it comes to webfonts, if you want to serve an accessible and high performance experience across device types it’s not as straightforward as just specifying your fonts in CSS then hoping for the best.

$$ in the DevTools Console

I learned something new today when developing in the Firefox Dev Tools console (although this applies to Chrome too)—something which was really useful and which I thought I’d share.

Basically, type $$('selector') into the console (replacing selector as desired) and it’ll give you back all matching elements on the page.

Stuffing the front end

Here’s Bridget Stewart, a developer from Ohio, with some thoroughly enjoyable “curmudgeonly” thoughts on why your website doesn’t necessarily need a Javascript framework.

Accessible modal dialogues in 2019

I previously noted Keith J Grant’s article on the HTML dialog element which promised a native means of handling popups and modal dialogues. I’ve not yet used dialog in production, partly because of spotty browser support (although there is a polyfill) but also partly because—for reasons I couldn’t quite put my finger on after reading the spec—it just didn’t feel like the finished article.

Promises in JavaScript

A brief explainer (for future-me and anyone else it helps) on what promises are and how to use them. Note: this is not an official definition, but rather one that works for me.

See all tags.

External Link Bookmark Note Entry Search