Snippets

These snippets are my attempt to save and organize various bits of code, best practices, and resources relating to web development and design. They also function as a to do list of sorts, for things I want to implement in my own code, but haven’t yet. The concept is inspired by Jeremy Keith’s links and CSS-Tricks, among other things. Enjoy.

An Inclusive Content Slider (Carousel)

Carousels (or ‘content sliders’) are like men. They are not literally all bad — some are even helpful and considerate. But I don’t trust anyone unwilling to acknowledge a glaring pattern of awfulness. Also like men, I appreciate that many of you would rather just avoid dealing with carousels, but often don’t have the choice. Hence this article.

Carousels don’t have to be bad, but we have a culture of making them bad. It is usually the features of carousels, rather than the underlying concept that is at fault. As with many things inclusive, the right solution is often not what you do but what you don’t do in the composition of the component.

[…]

  • Use list markup to group the slides together. Then screen reader users in ‘browse’ mode can use list navigation shortcuts to traverse them.
  • Provide a reasonable experience in HTML with CSS, then feature detect when enhancing with JavaScript.
  • Don’t preload content users are not likely to see. Defer until they perform an action to see it.
  • Provide generous touch targets for touch users on mobile / small screens.
  • If in doubt of a control’s (or widget’s) affordance, spell it out with instructions
  • If you are a man and got past the first paragraph without being personally offended: Congratulations! You do not see men and women as competing teams.

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Prevent image loading with MutationObserver

It turns out that if you place a MutationObserver in the <head> (or presumably even in the <body> before any <img> elements), and have it start observing right away it will be able to remove the src before the browser downloads the image, thus allowing for lazy loading and other optimizations.

I put this in <head> and normal <img> tags in <body>. - No image requests visible in Firefox dev tools - Safari shows requests but 0 bytes transferred - Chrome seems to get 4 kb over the wire before calling it quits

Javascript

const observer = new MutationObserver(mutations => {
	mutations.forEach(mutation => {
		Array.from(mutation.addedNodes)
			.filter(node => node.tagName === 'IMG')
			.forEach(img => {
				img.dataset.src = img.src;
				img.src = '';
			});
	});
});
 
observer.observe(document.documentElement, {
	childList: true,
	subtree: true
});

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Introduction to HTML5 form validation

I recently embarked on improving the client-side form validation for a client. There were about 400 lines of form validation code stuffed inside a 1000 line form_helper.js. I looked for lightweight form validation scripts but after some hemming and hawing I decided to try my hand (again) at native HTML5 Form Validation.

If you’ve ever experimented with HTML5 Form Validation, you’ve probably been disappointed. The out-of-box experience isn’t quite what you want. Adding the required attribute to inputs works wonderfully. However the styling portion with input:invalid sorta sucks because empty inputs are trigger the :invalid state, even before the user has interacted with the page.

I finally sat down and spent a couple days trying to make HTML5 Form Validation work the way I want it. I had the following goals:

  1. Leverage browser-level feedback, free focus management and accessible labelling
  2. Only validate inputs on submit
  3. Styling with .error class

With this wishlist in hand, I set off and found a solution that works with only 6 lines of code.

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Network based image loading using the Network Information API in Service Worker

Recently, Chromium improved their implementation of navigator.connection by adding three new attributes: effectiveType, downlink and rtt.

Before that, the available attributes were downLinkMax and type. With these two attributes you couldn’t really tell if the connection was fast or slow. The navigator.connection.type may tell us a user is using WiFi, but this doesn’t say anything about the real connection speed, as they may be using a hot spot and the connection is in fact 2G.

With the addition of effectiveType we are finally able to get the real connection type. There are four different types (slow-2g, 2g, 3g and 4g) and they are described this way by the Web Incubator Community Group:

slow-2g: The network is suited for small transfers only such as text-only pages.
2g: The network is suited for transfers of small images.
3g: The network is suited for transfers of large assets such as high resolution images, audio, and SD video.
4g: The network is suited for HD video, real-time video, etc.

Let’s see how we can improve user experience by delivering images based on available connection speed.

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Vannevar Bush’s Memex

Every now and then, I like to revisit Vannevar Bush’s classic article from the July 1945 edition of the Atlantic Monthly called As We May Think in which he describes a theoretical machine called the memex.

A memex is a device in which an individual stores all his books, records, and communications, and which is mechanized so that it may be consulted with exceeding speed and flexibility. It is an enlarged intimate supplement to his memory.

It consists of a desk, and while it can presumably be operated from a distance, it is primarily the piece of furniture at which he works. On the top are slanting translucent screens, on which material can be projected for convenient reading. There is a keyboard, and sets of buttons and levers. Otherwise it looks like an ordinary desk.

1945! Apart from its analogue rather than digital nature, it’s a remarkably prescient vision. In particular, there’s the idea of “associative trails”:

Wholly new forms of encyclopedias will appear, ready made with a mesh of associative trails running through them, ready to be dropped into the memex and there amplified. The lawyer has at his touch the associated opinions and decisions of his whole experience, and of the experience of friends and authorities.

[…]

And now I’m using the World Wide Web, a hypermedia system that takes in the whole planet, to create an associative trail. In this post, I’m linking (without asking anyone for permission) to six different sources, and in doing so, I’m creating a unique associative trail. And because this post has a URL (that won’t change), you are free to take it and make it part of your own associative trail on your digital memex.

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How to Disable Links

The topic of disabling links popped up at my work the other day. Somehow, a “disabled” anchor style was added to our typography styles last year when I wasn’t looking. There is a problem though: there is no real way to disable an <a> link (with a valid href attribute) in HTML. Not to mention, why would you even want to? Links are the basis of the web.

At a certain point, it looked like my co-workers were not going to accept this fact, so I started thinking of how this could be accomplished. Knowing that it would take a lot, I wanted to prove that it was not worth the effort and code to support such an unconventional interaction, but I feared that by showing it could be done they would ignore all my warnings and just use my example as proof that it was OK. This hasn’t quite shaken out for me yet, but I figured we could go through my research.

First, things first:

Just don’t do it.

A disabled link is not a link, it’s just text. You need to rethink your design if it calls for disabling a link.

[…]

Surefire way: remove the href

If you have decided that you are going to ignore my warning and proceed with disabling a link, then removing the href attribute is the best way I know how.

Straight from the official Hyperlink spec:

The href attribute on a and area elements is not required; when those elements do not have href attributes they do not create hyperlinks.

An easier to understand definition from MDN:

This attribute may be omitted (as of HTML5) to create a placeholder link. A placeholder link resembles a traditional hyperlink, but does not lead anywhere.

See the source link on more complex stuff involving disabling click/tap/keyboard interactions via JavaScript.

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How many people have JavaScript disabled or unavailable?

In 2013, the UK’s Government Digital Service did an experiment to determine how many of their users weren’t receiving JavaScript. You might assume, as I did years ago, that the only two options were either that users would have JavaScript enabled, or have disabled it explicitly via their browser’s settings or an addon. Unfortunately, those aren’t the only two options. The majority of users that don’t receive JavaScript likely don’t do so by choice.

They found that 1.1% of users didn’t execute their JavaScript test. Of those, only 0.2% either explicitly disabled JavaScript or used a browser that didn’t support it. The remainingly 0.9% did not indicate they didn’t support JavaScript, but were not executing the test.

‘noscript’ tags will only be followed by browsers that explicitly have JavaScript disabled or don’t support JavaScript at all. So a significant number of people had a JavaScript enabled browser but still didn’t run the scripts successfully.

It’s hard to know exactly why these browsers didn’t run the JavaScript, but a number of possible reasons are:

  • corporate or local blocking or stripping of JavaScript elements
  • existing JavaScript errors in the browser (ie from browser add-ons, toolbars etc)
  • page being left between requesting the base image and the script/noscript image
  • browsers that pre-load pages they incorrectly predict you will visit
  • network errors, especially on mobile devices
  • any undoubtedly many more I haven’t even thought about…

The takeaway? Do not assume that everyone has JavaScript, or will have it execute reliably even if they haven’t disabled it.

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Using SVG as image placeholders

Two SVG-based placeholders composed of polygons in the rough shape of of a photo of a person. The first placeholder is very abstract with few polygons, while the second contains more polygons and looks closer to the real photo.

I’m passionate about image performance optimisation and making images load fast on the web. One of the most interesting areas of exploration is placeholders: what to show when the image hasn’t loaded yet.

During the last days I have come across some loading techniques that use SVG, and I would like to describe them in this post.

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