Journal tags: custom

I’ve been deep-diving into HTML web components over the past few weeks. I decided to refactor the JavaScript on The Session to use custom elements wherever it made sense.

I really enjoyed doing this, even though the end result for users is exactly the same as before. This was one of those refactors that was for me, and also for future me. The front-end codebase looks a lot more understandable and therefore maintainable.

Most of the JavaScript on The Session is good ol’ DOM scripting. Listen for events; when an event happens, make some update to some element. It’s the kind of stuff we might have used jQuery for in the past.

Chris invoked Betteridge’s law of headlines recently by asking Will Web Components replace React and Vue? I agree with his assessment. The reactivity you get with full-on frameworks isn’t something that web components offer. But I do think web components can replace jQuery and other approaches to scripting the DOM.

I’ve written about my preferred way to do DOM scripting: element.target.closest. One of the advantages to that approach is that even if the DOM gets updated—perhaps via Ajax—the event listening will still work.

Well, this is exactly the kind of thing that custom elements take care of for you. The connectedCallback method gets fired whenever an instance of the custom element is added to the document, regardless of whether that’s in the initial page load or later in an Ajax update.

So my client-side scripting style has updated over time:

1. Adding event handlers directly to elements.
2. Adding event handlers to the document and using event.target.closest.
3. Wrapping elements in a web component that handles the event listening.

None of these progressions were particularly ground-breaking or allowed me to do anything I couldn’t do previously. But each progression improved the resilience and maintainability of my code.

Like Chris, I’m using web components to progressively enhance what’s already in the markup. In fact, looking at the code that Chris is sharing, I think we may be writing some very similar web components!

A few patterns have emerged for me…

Naming custom elements

Naming things is famously hard. Every time you make a new custom element you have to give it a name that includes a hyphen. I settled on the convention of using the first part of the name to echo the element being enhanced.

If I’m adding an enhancement to a button element, I’ll wrap it in a custom element that starts with button-. I’ve now got custom elements like button-geolocate, button-confirm, button-clipboard and so on.

Likewise if the custom element is enhancing a link, it will begin with a-. If it’s enhancing a form, it will begin with form-.

The name of the custom element tells me how it’s expected to be used. If I find myself wrapping a div with button-geolocate I shouldn’t be surprised when it doesn’t work.

Naming attributes

You can use any attributes you want on a web component. You made up the name of the custom element and you can make up the names of the attributes too.

I’m a little nervous about this. What if HTML ends up with a new global attribute in the future that clashes with something I’ve invented? It’s unlikely but it still makes me wary.

So I use data- attributes. I’ve already got a hyphen in the name of my custom element, so it makes sense to have hyphens in my attributes too. And by using data- attributes, the browser gives me automatic reflection of the value in the dataset property.

Instead of getting a value with this.getAttribute('maximum') I get to use this.dataset.maximum. Nice and neat.

The single responsibility principle

My favourite web components aren’t all-singing, all-dancing powerhouses. Rather they do one thing, often a very simple thing.

Here are some examples:

• Jason’s aria-collapsable for toggling the display of one element when you click on another.
• David’s play-button for adding a play button to an audio or video element.
• Chris’s ajax-form for sending a form via Ajax instead of a full page refresh.
• Jim’s user-avatar for adding a tooltip to an image.
• Zach’s table-saw for making tables responsive.

All of those are HTML web components in that they extend your existing markup rather than JavaScript web components that are used to replace HTML. All of those are also unambitious by design. They each do one thing and one thing only.

But what if my web component needs to do two things?

I make two web components.

The beauty of custom elements is that they can be used just like regular HTML elements. And the beauty of HTML is that it’s composable.

What if you’ve got some text that you want to be a level-three heading and also a link? You don’t bemoan the lack of an element that does both things. You wrap an a element in an h3 element.

The same goes for custom elements. If I find myself adding multiple behaviours to a single custom element, I stop and ask myself if this should be multiple custom elements instead.

Take some of those button- elements I mentioned earlier. One of them copies text to the clipboard, button-clipboard. Another throws up a confirmation dialog to complete an action, button-confirm. Suppose I want users to confirm when they’re copying something to their clipboard (not a realistic example, I admit). I don’t have to create a new hybrid web component. Instead I wrap the button in the two existing custom elements.

Rather than having a few powerful web components, I like having lots of simple web components. The power comes with how they’re combined. Like Unix pipes. And it has the added benefit of stopping my code getting too complex and hard to understand.

Communicating across components

Okay, so I’ve broken all of my behavioural enhancements down into single-responsibility web components. But what if one web component needs to have awareness of something that happens in another web component?

Here’s an example from The Session: the results page when you search for sessions in London.

There’s a map. That’s one web component. There’s a list of locations. That’s another web component. There are links for traversing backwards and forwards through the locations via Ajax. Those links are in web components too.

I want the map to update when the list of locations changes. Where should that logic live? How do I get the list of locations to communicate with the map?

Events!

When a list of locations is added to the document, it emits a custom event that bubbles all the way up. In fact, that’s all this component does.

You can call the event anything you want. It could be a newLocations event. That event is dispatched in the connectedCallback of the component.

Meanwhile in the map component, an event listener listens for any newLocations events on the document. When that event handler is triggered, the map updates.

The web component that lists locations has no idea that there’s a map on the same page. It doesn’t need to. It just needs to dispatch its event, no questions asked.

There’s nothing specific to web components here. Event-driven programming is a tried and tested approach. It’s just a little easier to do thanks to the connectedCallback method.

I’m documenting all this here as a snapshot of my current thinking on HTML web components when it comes to:

• naming custom elements,
• naming attributes,
• the single responsibility principle, and
• communicating across components.

I may well end up changing my approach again in the future. For now though, these ideas are serving me well.

Those HTML web components I made for date inputs are very simple. All they do is slightly extend the behaviour of the existing input elements.

This would be the ideal use-case for the is attribute:

<input is="input-date-future" type="date">

Alas, Apple have gone on record to say that they will never ship support for customized built-in elements.

So instead we have to make HTML web components by wrapping existing elements in new custom elements:

<input-date-future>
  <input type="date">
<input-date-future>

The end result is the same. Mostly.

Because there’s now an additional element in the DOM, there could be unexpected styling implications. Like, suppose the original element was direct child of a flex or grid container. Now that will no longer be true.

So something I’ve started doing with HTML web components like these is adding something like this inside the connectedCallback method:

connectedCallback() {
    this.style.display = 'contents';
  …
}

This tells the browser that, as far as styling is concerned, there’s nothing to see here. Move along.

Or you could (and probably should) do it in your stylesheet instead:

input-date-future {
  display: contents;
}

Just to be clear, you should only use display: contents if your HTML web component is augmenting what’s within it. If you add any behaviours or styling to the custom element itself, then don’t add this style declaration.

It’s a bit of a hack to work around the lack of universal support for the is attribute, but it’ll do.

I had the opportunity to trim some code from The Session recently. That’s always a good feeling.

In this case, it was a progressive enhancement pattern that was no longer needed. Kind of like removing a polyfill.

There are a couple of places on the site where you can input a date. This is exactly what input type="date" is for. But when I was making the interface, the support for this type of input was patchy.

So instead the interface used three select dropdowns: one for days, one for months, and one for years. Then I did a bit of feature detection and if the browser supported input type="date", I replaced the three selects with one date input.

It was a little fiddly but it worked.

Fast forward to today and input type="date" is supported across the board. So I threw away the JavaScript and updated the HTML to use date inputs by default. Nice!

I was discussing date inputs recently when I was talking to students in Amsterdam:

They’re given a PDF inheritance-tax form and told to convert it for the web.

That form included dates. The dates were all in the past so the students wanted to be able to set a max value on the datepicker. Ideally that should be done on the server, but it would be nice if you could easily do it in the browser too.

Wouldn’t it be nice if you could specify past dates like this?

<input type="date" max="today">

Or for future dates:

<input type="date" min="today">

Alas, no such syntactic sugar exists in HTML so we need to use JavaScript.

This seems like an ideal use-case for HTML web components:

Instead of all-singing, all-dancing web components, it feels a lot more elegant to use web components to augment your existing markup with just enough extra behaviour.

In this case, it would be nice to augment an existing input type="date" element. Something like this:

 <input-date-past>
   <input type="date">
 </input-date-past>

Here’s the JavaScript that does the augmentation:

 customElements.define('input-date-past', class extends HTMLElement {
     constructor() {
         super();
     }
     connectedCallback() {
         this.querySelector('input[type="date"]').setAttribute('max', new Date().toISOString().substring(0,10));
     }
 });

That’s it.

Here’s a CodePen where you can see it in action along with another HTML web component for future dates called, you guessed it, input-date-future.

See the Pen Date input HTML web components by Jeremy Keith (@adactio) on CodePen.

Web components have been around for quite a while, but it feels like they’re having a bit of a moment right now.

It turns out that the best selling point for web components was “wait and see.” For everyone who didn’t see the benefit of web components over being locked into a specific framework, time is proving to be a great teacher.

It’s not just that web components are portable. They’re also web standards, which means they’ll be around as long as web browsers. No framework can make that claim. As Jake Lazaroff puts it, web components will outlive your JavaScript framework.

At this point React is legacy technology, like Angular. Lots of people are still using it, but nobody can quite remember why. The decision-makers in organisations who chose to build everything with React have long since left. People starting new projects who still decide to build on React are doing it largely out of habit.

Others are making more sensible judgements and, having been bitten by lock-in in the past, are now giving web components a go.

If you’re one of those people making the move from React to web components, there’ll certainly be a bit of a learning curve, but that would be true of any technology change.

I have a suggestion for you if you find yourself in this position. Try not to bring React’s mindset with you.

I’m talking about the way React components are composed. There’s often lots of props doing heavy lifting. The actual component element itself might be empty.

If you want to apply that model to web components, you can. Lots of people do. It’s not unusual to see web components in the wild that look like this:

<my-component></my-component>

The custom element is just a shell. All the actual power is elsewhere. It’s in the JavaScript that does all kinds of clever things with the shadow DOM, templates, and slots.

There is another way. Ask, as Robin does, “what would HTML do?”

Think about composibility with existing materials. Do you really need to invent an entirely new component from scratch? Or can you use HTML up until it reaches its limit and then enhance the markup?

Robin writes:

I don’t think we should see web components like the ones you might find in a huge monolithic React app: your Button or Table or Input components. Instead, I’ve started to come around and see Web Components as filling in the blanks of what we can do with hypertext: they’re really just small, reusable chunks of code that extends the language of HTML.

Dave talks about how web components can be HTML with superpowers. I think that’s a good attitude to have. Instead of all-singing, all-dancing web components, it feels a lot more elegant to use web components to augment your existing markup with just enough extra behaviour.

Where does the shadow DOM come into all of this? It doesn’t. And that’s okay. I’m not saying it should be avoided completely, but it should be a last resort. See how far you can get with the composibility of regular HTML first.

Eric described his recent epiphany with web components. He created a super-slider custom element that wraps around an existing label and input type="range":

You just take some normal HTML markup, wrap it with a custom element, and then write some JS to add capabilities which you can then style with regular CSS!  Everything’s of the Light Side of the Web.  No need to pierce the Vale of Shadows or whatever.

When you wrap some existing markup in a custom element and then apply some new behaviour with JavaScript, technically you’re not doing anything you couldn’t have done before with some DOM traversal and event handling. But it’s less fragile to do it with a web component. It’s portable. It obeys the single responsibility principle. It only does one thing but it does it well.

Jim created an icon-list custom element that wraps around a regular ul populated with li elements. But he feels almost bashful about even calling it a web component:

Maybe I shouldn’t be using the term “web component” for what I’ve done here. I’m not using shadow DOM. I’m not using the templates or slots. I’m really only using custom elements to attach functionality to a specific kind of component.

I think what Eric and Jim are doing is exemplary. See also Zach’s web components.

At the end of his post, Eric says he’d like a nice catchy term for these kinds of web components. In Dave’s catalogue of web components, they’re called “element extensions.” I like that. It’s pretty catchy.

Or we could call them “HTML web components.” If your custom element is empty, it’s not an HTML web component. But if you’re using a custom element to extend existing markup, that’s an HTML web component.

React encouraged a mindset of replacement: “forgot what browsers can do; do everything in a React component instead, even if you’re reinventing the wheel.”

HTML web components encourage a mindset of augmentation instead.

I had a lot of fun making the website for Patterns Day.

If you’re interested in the tech stack, here’s what I used:

1. HTML
2. CSS

Actually, technically it’s all HTML because the styles are inside a style element rather than a separate style sheet, but you know what I mean. Also, there is technically some JavaScript but all it does is register a service worker that takes care of caching and going offline.

I didn’t use any build tools. There was no pipeline. There is no node_modules folder filling up my hard drive. Nothing was automated. The website was hand-crafted the long hard stupid way.

I started with the content. I wrote out the words and marked them up with the most appropriate HTML elements.

Time to layer on the presentation.

For the design, I turned to Michelle for help. I gave her a brief, describing the vibe of the conference, and asked her to come up with an appropriate visual language.

Crucially, I asked her not to design a website. Instead I asked her to think about other places where this design language might be used: a poster, social media, anything but a website.

Partly I was doing this for my own benefit. If you give me a pixel-perfect design for a web page and tell me to code it up, either I won’t do it or I won’t enjoy it. I just don’t get any motivation out of that kind of direct one-to-one translation.

But give me guardrails, give me constraints, give me boundary conditions, and off I go!

Michelle was very gracious in dealing with such a finicky client as myself (“Can you try this other direction?”, “Hmm… I think I preferred the first one after all!”) She delivered a colour palette, a type scale, typeface choices, and some wonderful tiling patterns …it is Patterns Day after all!

With just a few extra lines of CSS, the basic typography was in place.

I started layering on the colours. Even though this was a one-page site, I still made liberal use of custom properties in the CSS. It just feels good to be able to update one value and see the results, well …cascade.

I had a lot of fun with the tiling background images. SVG was the perfect format for these. And because the tiles were so small in file size, I just inlined them straight into the CSS.

By this point, I felt like I was truly designing in the browser. Adjusting spacing, playing around with layout, and all that squishy stuff. Some of the best results came from happy accidents—the way that certain elements behaved at certain screen sizes would lead me into little experiments that yielded interesting results.

I’m not sure it’s possible to engineer that kind of serendipity in Figma. Figma was the perfect tool for exploring ideas around the visual vocabulary, and for handing over design decisions around colour, typography, and texture. But when it comes to how the content is going to behave on the World Wide Web, nothing beats a browser for fidelity.

By this point I was really sweating the details, like getting the logo just right and adjusting the type scale for different screen sizes. Needless to say, Utopia was a godsend for that.

I was also checking back in with Michelle to get her take on design decisions I was making.

I could’ve kept tinkering but the diminishing returns were a sign that it was time to put this out into the world.

It felt really good to work on a web page like this. It felt like I was getting my hands into the soil of the web. I don’t think it’s an accident that the result turned out to be very performant.

Getting hands-on like this stops me from getting rusty. And honestly, working with CSS these days is a joy. There’s such power to be had from using var() in combination with functions like calc() and clamp(). Layout is a breeze with flexbox and grid. Browser differences are practically non-existent. We’ve never had it so good.

Here’s something I noticed about my relationship to CSS; my brain has finally made the switch to logical properties. Now if I’m looking at some CSS and I see left, right, top, or bottom, it looks like a bug to me. Those directional properties feel loaded with assumptions whereas logical properties feel much more like working with the grain of the web.

I made the website for the Clearleft podcast last week. The design is mostly lifted straight from the rest of the Clearleft website. The main difference is the masthead. If the browser window is wide enough, there’s a background image on the right hand side.

I mostly added that because I felt like the design was a bit imbalanced without something there. On the home page, it’s a picture of me. Kind of cheesy. But the image can be swapped out. On other pages, there are different photos. All it takes is a different class name on that masthead.

I thought about having the image be completely random (and I still might end up doing this). I’d need to use a bit of JavaScript to choose a class name at random from a list of possible values. Something like this:

var names = ['jeremy','katie','rich','helen','trys','chris'];
var name = names[Math.floor(Math.random() * names.length)];
document.querySelector('.masthead').classList.add(name);

(You could paste that into the dev tools console to see it in action on the podcast site.)

Then I read something completely unrelated. Cassie wrote a fantastic article on her site called Making lil’ me - part 1. In it, she describes how she made the mouse-triggered animation of her avatar in the footer of her home page.

It’s such a well-written technical article. She explains the logic of what she’s doing, and translates that logic into code. Then, after walking you through the native code, she shows how you could use the Greeksock library to achieve the same effect. That’s the way to do it! Instead of saying, “Here’s a library that will save you time—don’t worry about how it works!”, she’s saying “Here’s it works without a library; here’s how it works with a library; now you can make an informed choice about what to use.” It’s a very empowering approach.

Anyway, in the article, Cassie demonstrates how you can use custom properties as a bridge between JavaScript and CSS. JavaScript reads the mouse position and updates some custom properties accordingly. Those same custom properties are used in CSS for positioning. Voila! Now you’ve got the position of an element responding to mouse movements.

That’s what made me think of the code snippet I wrote above to update a class name from JavaScript. I automatically thought of updating a class name because, frankly, that’s how I’ve always done it. I’d say about 90% of the DOM scripting I’ve ever done involves toggling the presence of class values: accordions, fly-out menus, tool-tips, and other progressive disclosure patterns.

That’s fine. But really, I should try to avoid touching the DOM at all. It can have performance implications, possibly triggering unnecessary repaints and reflows.

Now with custom properties, there’s a direct line of communication between JavaScript and CSS. No need to use the HTML as a courier.

This made me realise that I need to be aware of automatically reaching for a solution just because that’s the way I’ve done something in the past. I should step back and think about the more efficient solutions that are possible now.

It also made me realise that “CSS variables” is a very limiting way of thinking about custom properties. The fact that they can be updated in real time—in CSS or JavaScript—makes them much more powerful than, say, Sass variables (which are more like constants).

But I too have been guilty of underselling them. I almost always refer to them as “CSS custom properties” …but a lot of their potential comes from the fact that they’re not confined to CSS. From now on, I’m going to try calling them custom properties, without any qualification.

When I wrote about programming CSS to perform Sass colour functions I said this about the brilliant Lea Verou:

As so often happens when I’m reading something written by Lea—or seeing her give a talk—light bulbs started popping over my head (my usual response to Lea’s knowledge bombs is either “I didn’t know you could do that!” or “I never thought of doing that!”).

Well, it happened again. This time I was reading her post about hybrid positioning with CSS variables and max() . But the main topic of the post wasn’t the part that made go “Huh! I never knew that!”. Towards the end of her article she explained something about the way that browsers evaluate CSS custom properties:

The browser doesn’t know if your property value is valid until the variable is resolved, and by then it has already processed the cascade and has thrown away any potential fallbacks.

I’m used to being able to rely on the cascade. Let’s say I’m going to set a background colour on paragraphs:

p {
  background-color: red;
  background-color: color(display-p3 1 0 0);
}

First I’ve set a background colour using a good ol’ fashioned keyword, supported in browsers since day one. Then I declare the background colour using the new-fangled color() function which is supported in very few browsers. That’s okay though. I can confidently rely on the cascade to fall back to the earlier declaration. Paragraphs will still have a red background colour.

But if I store the background colour in a custom property, I can no longer rely on the cascade.

:root {
  --myvariable: color(display-p3 1 0 0);
}
p {
  background-color: red;
  background-color: var(--myvariable);
}

All I’ve done is swapped out the hard-coded color() value for a custom property but now the browser behaves differently. Instead of getting a red background colour, I get the browser default value. As Lea explains:

…it will make the property invalid at computed value time.

The spec says:

When this happens, the computed value of the property is either the property’s inherited value or its initial value depending on whether the property is inherited or not, respectively, as if the property’s value had been specified as the unset keyword.

So if a browser doesn’t understand the color() function, it’s as if I’ve said:

background-color: unset;

This took me by surprise. I’m so used to being able to rely on the cascade in CSS—it’s one of the most powerful and most useful features in this programming language. Could it be, I wondered, that the powers-that-be have violated the principle of least surprise in specifying this behaviour?

But a note in the spec explains further:

Note: The invalid at computed-value time concept exists because variables can’t “fail early” like other syntax errors can, so by the time the user agent realizes a property value is invalid, it’s already thrown away the other cascaded values.

Ah, right! So first of all browsers figure out the cascade and then they evaluate custom properties. If a custom property evaluates to gobbledygook, it’s too late to figure out what the cascade would’ve fallen back to.

Thinking about it, this makes total sense. Remember that CSS custom properties aren’t like Sass variables. They aren’t evaluated once and then set in stone. They’re more like let than const. They can be updated in real time. You can update them from JavaScript too. It’s entirely possible to update CSS custom properties rapidly in response to events like, say, the user scrolling or moving their mouse. If the browser had to recalculate the cascade every time a custom property didn’t evaluate correctly, I imagine it would be an enormous performance bottleneck.

So even though this behaviour surprised me at first, it makes sense on reflection.

I’ve probably done a terrible job explaining the behaviour here, so I’ve made a Codepen. Although that may also do an equally terrible job.

(Thanks to Amber for talking through this with me and encouraging me to blog about it. And thanks to Lea for expanding my mind. Again.)

I wrote recently about moving away from Sass to using native CSS features. I had this to say on the topic of mixins in Sass:

These can be very useful, but now there’s a lot that you can do just in CSS with calc(). The built-in darken() and lighten() mixins are handy though when it comes to colours.

I know we will be getting these in the future but we’re not there yet with CSS.

Anyway, I had all this in the back of my mind when I was reading Lea’s excellent feature in this month’s Increment: A user’s guide to CSS variables. She’s written about a really clever technique of combining custom properites with hsl() colour values for creating colour palettes. (See also: Una’s post on dynamic colour theming with pure CSS.)

As so often happens when I’m reading something written by Lea—or seeing her give a talk—light bulbs started popping over my head (my usual response to Lea’s knowledge bombs is either “I didn’t know you could do that!” or “I never thought of doing that!”).

I immediately set about implementing this technique over on The Session. The trick here is to use separate custom properties for the hue, saturation, and lightness parts of hsl() colour values. Then, when you want to lighten or darken the colour—say, on hover—you can update the lightness part.

I’ve made a Codepen to show what I’m doing.

Let’s say I’m styling a button element. I make custom propertes for hsl() values:

button {
  --button-colour-hue: 19;
  --button-colour-saturation: 82%;
  --button-colour-lightness: 38%;
  background-color: hsl(
    var(--button-colour-hue),
    var(--button-colour-saturation),
    var(--button-colour-lightness)
  );
}

For my buttons, I want the borders to be slightly darker than the background colour. When I was using Sass, I used the darken() function to this. Now I use calc(). Here’s how I make the borders 10% darker:

border-color: hsl(
  var(--button-colour-hue),
  var(--button-colour-saturation),
  calc(var(--button-colour-lightness) - 10%)
);

That calc() function is substracting a percentage from a percentage: 38% minus 10% in this case. The borders will have a lightness of 28%.

I make the bottom border even darker and the top border lighter to give a feeling of depth.

button

On The Session there’s a “cancel” button style that’s deep red.

cancel

Here’s how I set its colour:

.cancel {
  --button-colour-hue: 0;
  --button-colour-saturation: 100%;
  --button-colour-lightness: 40%;
}

That’s it. The existing button declarations take care of assigning the right shades for the border colours.

Here’s another example. Site admins see buttons for some actions only available to them. I want those buttons to have their own colour:

.admin {
  --button-colour-hue: 45;
  --button-colour-saturation: 100%;
  --button-colour-lightness: 40%;
}

admin

You get the idea. It doesn’t matter how many differently-coloured buttons I create, the effect of darkening or lightening their borders is all taken care of.

So it turns out that the lighten() and darken() functions from Sass are available to us in CSS by using a combination of custom properties, hsl(), and calc().

I’m also using this combination to lighten or darken background and border colours on :hover. You can poke around the Codepen if you want to see that in action.

I love seeing the combinatorial power of these different bits of CSS coming together. It really is a remarkably powerful programming language.

Trys and James recently unveiled their Utopia project. They’ve been tinkering away at it behind the scenes for quite a while now.

You can check out the website and read the blog to get the details of how it accomplishes its goal:

Elegantly scale type and space without breakpoints.

I may well be biased, but I really like this project. I’ve been asking myself why I find it so appealing. Here are a few of the attributes of Utopia that strike a chord with me…

It’s collaborative

Collaboration is at the heart of Clearleft’s work. I know everyone says that, but we’ve definitely seen a direct correlation: projects with high levels of collaboration are invariably more successful than projects where people are siloed.

The genesis for Utopia came about after Trys and James worked together on a few different projects. It’s all too easy to let design and development splinter off into their own caves, but on these projects, Trys and James were working (literally) side by side. This meant that they could easily articulate frustrations to one another, and more important, they could easily share their excitement.

The end result of their collaboration is some very clever code. There’s an irony here. This code could be used to discourage collaboration! After all, why would designers and developers sit down together if they can just pass these numbers back and forth?

But I don’t think that Utopia will appeal to designers and developers who work in that way. Born in the spirit of collaboration, I suspect that it will mostly benefit people who value collaboration.

It’s intrinsic

If you’re a control freak, you may not like Utopia. The idea is that you specify the boundaries of what you’re trying to accomplish—minimum/maximum font sizes, minumum/maximum screen sizes, and some modular scales. Then you let the code—and the browser—do all the work.

On the one hand, this feels like surrending control. But on the other hand, because the underlying system is so robust, it’s a way of guaranteeing quality, even in situations you haven’t accounted for.

If someone asks you, “What size will the body copy be when the viewport is 850 pixels wide?”, your answer would have to be “I don’t know …but I do know that it will be appropriate.”

This feels like a very declarative way of designing. It reminds me of the ethos behind Andy and Heydon’s site, Every Layout. They call it algorithmic layout design:

Employing algorithmic layout design means doing away with @media breakpoints, “magic numbers”, and other hacks, to create context-independent layout components. Your future design systems will be more consistent, terser in code, and more malleable in the hands of your users and their devices.

See how breakpoints are mentioned as being a very top-down approach to layout? Remember the tagline for Utopia, which aims for fluid responsive design?

Elegantly scale type and space without breakpoints.

Unsurprisingly, Andy really likes Utopia:

As the co-author of Every Layout, my head nearly fell off from all of the nodding when reading this because this is the exact sort of approach that we preach: setting some rules and letting the browser do the rest.

Heydon describes this mindset as automating intent. I really like that. I think that’s what Utopia does too.

As Heydon said at Patterns Day:

Be your browser’s mentor, not its micromanager.

The idea is that you give it rules, you give it axioms or principles to work on, and you let it do the calculation. You work with the in-built algorithms of the browser and of CSS itself.

This is all possible thanks to improvements to CSS like calc, flexbox and grid. Jen calls this approach intrinsic web design. Last year, I liveblogged her excellent talk at An Event Apart called Designing Intrinsic Layouts.

Utopia feels like it has the same mindset as algorithmic layout design and intrinsic web design. Trys and James are building on the great work already out there, which brings me to the final property of Utopia that appeals to me…

It’s iterative

There isn’t actually much that’s new in Utopia. It’s a combination of existing techniques. I like that. As I said recently:

I’m a great believer in the HTML design principle, Evolution Not Revolution:

It is better to evolve an existing design rather than throwing it away.

First of all, Utopia uses the idea of modular scales in typography. Tim Brown has been championing this idea for years.

Then there’s the idea of typography being fluid and responsive—just like Jason Pamental has been speaking and writing about.

On the code side, Utopia wouldn’t be possible without the work of Mike Reithmuller and his breakthroughs on responsive and fluid typography, which led to Tim’s work on CSS locks.

Utopia takes these building blocks and combines them. So if you’re wondering if it would be a good tool for one of your projects, you can take an equally iterative approach by asking some questions…

Are you using fluid type?

Do your font-sizes increase in proportion to the width of the viewport? I don’t mean in sudden jumps with @media breakpoints—I mean some kind of relationship between font size and the vw (viewport width) unit. If so, you’re probably using some kind of mechanism to cap the minimum and maximum font sizes—CSS locks.

I’m using that technique on Resilient Web Design. But I’m not changing the relative difference between different sized elements—body copy, headings, etc.—as the screen size changes.

Are you using modular scales?

Does your type system have some kind of ratio that describes the increase in type sizes? You probably have more than one ratio (unlike Resilient Web Design). The ratio for small screens should probably be smaller than the ratio for big screens. But rather than jump from one ratio to another at an arbitrary breakpoint, Utopia allows the ratio to be fluid.

So it’s not just that font sizes are increasing as the screen gets larger; the comparative difference is also subtly changing. That means there’s never a sudden jump in font size at any time.

Are you using custom properties?

A technical detail this, but the magic of Utopia relies on two powerful CSS features: calc() and custom properties. These two workhorses are used by Utopia to generate some CSS that you can stick at the start of your stylesheet. If you ever need to make changes, all the parameters are defined at the top of the code block. Tweak those numbers and watch everything cascade.

You’ll see that there’s one—and only one—media query in there. This is quite clever. Usually with CSS locks, you’d need to have a media query for every different font size in order to cap its growth at the maximum screen size. With Utopia, the maximum screen size—100vw—is abstracted into a variable (a custom property). The media query then changes its value to be the upper end of your CSS lock. So it doesn’t matter how many different font sizes you’re setting: because they all use that custom property, one single media query takes care of capping the growth of every font size declaration.

If you’re already using CSS locks, modular scales, and custom properties, Utopia is almost certainly going to be a good fit for you.

If you’re not yet using those techniques, but you’d like to, I highly recommend using Utopia on your next project.

Here’s a tiny lesson that I picked up from Trys that I’d like to share with you…

I was working on some upcoming changes to the Clearleft site recently. One particular component needed some SVG background images. I decided I’d inline the SVGs in the CSS to avoid extra network requests. It’s pretty straightforward:

.myComponent {
    background-image: url('data:image/svg+xml;utf8,<svg> ... </svg>');
}

You can basically paste your SVG in there, although you need to a little bit of URL encoding: I found that converting # to %23 to was enough for my needs.

But here’s the thing. My component had some variations. One of the variations had multiple background images. There was a second background image in addition to the first. There’s no way in CSS to add an additional background image without writing a whole background-image declaration:

.myComponent--variant {
    background-image: url('data:image/svg+xml;utf8,<svg> ... </svg>'), url('data:image/svg+xml;utf8,<svg> ... </svg>');
}

So now I’ve got the same SVG source inlined in two places. That negates any performance benefits I was getting from inlining in the first place.

That’s where Trys comes in. He shared a nifty technique he uses in this exact situation: put the SVG source into a custom property!

:root {
    --firstSVG: url('data:image/svg+xml;utf8,<svg> ... </svg>');
    --secondSVG: url('data:image/svg+xml;utf8,<svg> ... </svg>');
}

Then you can reference those in your background-image declarations:

.myComponent {
    background-image: var(--firstSVG);
}
.myComponent--variant {
    background-image: var(--firstSVG), var(--secondSVG);
}

Brilliant! Not only does this remove any duplication of the SVG source, it also makes your CSS nice and readable: no more big blobs of SVG source code in the middle of your style sheet.

You might be wondering what will happen in older browsers that don’t support CSS custom properties (that would be Internet Explorer 11). Those browsers won’t get any background image. Which is fine. It’s a background image. Therefore it’s decoration. If it were an important image, it wouldn’t be in the background.

Progressive enhancement, innit?

Cassie posted a neat tiny lesson that she’s written a reduced test case for.

Here’s the situation…

CSS custom properties are fantastic. You can drop them in just about anywhere that a property takes a value.

Here’s an example of defining a custom property for a length:

:root {
    --my-value: 1em;
}

Then I can use that anywhere I’d normally give something a length:

.my-element {
    margin-bottom: var(--my-value);
}

I went a bit overboard with custom properties on the new Patterns Day site. I used them for colour values, font stacks, and spacing. Design tokens, I guess. They really come into their own when you combine them with media queries: you can update the values of the custom properties based on screen size …without having to redefine where those properties are applied. Also, they can be updated via JavaScript so they make for a great common language between CSS and JavaScript: you can define where they’re used in your CSS and then update their values in JavaScript, perhaps in response to user interaction.

But there are a few places where you can’t use custom properties. You can’t, for example, use them as part of a media query. This won’t work:

@media all and (min-width: var(--my-value)) {
    ...
}

You also can’t use them in generated content if the value is a number. This won’t work:

:root {
    --number-value: 15;
}
.my-element::before {
    content: var(--number-value);
}

Fair enough. Generated content in CSS is kind of a strange beast. Eric delivered an entire hour-long talk at An Event Apart in Seattle on generated content.

But Cassie found a workaround if the value you want to put into that content property is numeric. The CSS counter value is a kind of generated content—the numbers that appear in front of ordered list items. And you can control the value of those numbers from CSS.

CSS counters work kind of like variables. You name them and assign values to them using the counter-reset property:

.my-element {
    counter-reset: mycounter 15;
}

You can then reference the value of mycounter in a content property using the counter value:

.my-element {
    content: counter(mycounter);
}

Cassie realised that even though you can’t pass in a custom property directly to generated content, you can pass in a custom property to the counter-reset property. So you can do this:

:root {
    --number-value: 15;
}
.my-element {
    counter-reset: mycounter var(--number-value);
    content: counter(mycounter);
}

In a roundabout way, this allows you to use a custom property for generated content!

I realise that the use cases are pretty narrow, but I can’t help but be impressed with the thinking behind this. Personally, I would’ve just read that generated content doesn’t accept custom properties and moved on. I would’ve given up quickly. But Cassie took a step back and found a creative pass-the-parcel solution to the problem.

I feel like this is a hack in the best sense of the word: a creatively improvised solution to a problem or limitation.

I was trying to display the numeric value stored in a CSS variable inside generated content… Turns out you can’t do that. But you can do this… codepen.io/cassie-codes/p… (not saying you should, but you could)

Adam Onishi has written up his thoughts on web components and progressive enhancements, following on from a discussion we were having on Slack. He shares a lot of the same frustrations as I do.

Two years ago, I said:

I have conflicting feelings about Web Components. I am simultaneously very excited and very nervous.

I still feel that way. In theory, web components are very exciting. In practice, web components are very worrying. The worrying aspect comes from the treatment of backwards compatibility.

It all comes down to the way custom elements work. When you make up a custom element, it’s basically a span.

<fancy-select></fancy-select>

Then, using JavaScript with ShadowDOM, templates, and the other specs that together make up the web components ecosystem, you turn that inert span-like element into something all-singing and dancing. That’s great if the browser supports those technologies, and the JavaScript executes successfully. But if either of those conditions aren’t met, what you’re left with is basically a span.

One of the proposed ways around this was to allow custom elements to extend existing elements (not just spans). The proposed syntax for this was an is attribute.

<select is="fancy-select">...</select>

Browser makers responded to this by saying “Nah, that’s too hard.”

To be honest, I had pretty much given up on the is functionality ever seeing the light of day, but Monica has rekindled my hope:

@adactio I will go to every standards meeting until I get it done, because otherwise we are hosed for <form> and web components.

— Monica Dinosaurescu (@notwaldorf) June 16, 2016

Still, I’m not holding my breath for this kind of declarative extensibility landing in browsers any time soon. Instead, a JavaScript-based way of extending existing existing elements is currently the only way of piggybacking on all the accessible behavioural goodies you get with native elements.

class FancySelect extends HTMLSelectElement

But this imperative approach fails completely if custom elements aren’t supported, or if the JavaScript fails to execute. Now you’re back to having spans.

The presentation on web components at the Progressive Web Apps Dev Summit referred to this JavaScript-based extensibility as “progressively enhancing what’s already available”, which is a bit of a stretch, given how completely it falls apart in older browsers. It was kind of a weird talk, to be honest. After fifteen minutes of talking about creating elements entirely from scratch, there was a minute or two devoted to the is attribute and extending existing elements …before carrying as though those two minutes never happened.

But even without any means of extending existing elements, it should still be possible to define custom elements that have some kind of fallback in non-supporting browsers:

<fancy-select>
 <select>...</select>
</fancy-select>

In that situation, you at least get a regular ol’ select element in older browsers (or in modern browsers before the JavaScript kicks in and uplifts the custom element).

Adam has a great example of this in his post:

I’ve been thinking of a gallery component lately, where you’d have a custom element, say <o-gallery> for want of a better example, and simply populate it with images you want to display, with custom elements and shadow DOM you can add all the rest, controls/layout etc. Markup would be something like:

<o-gallery>
 <img src="">
 <img src="">
 <img src="">
</o-gallery>

If none of the extra stuff loads, what do we get? Well you get 3 images on the page. You still get the content, but just none of the fancy interactivity.

Yes! This, in my opinion, is how we should be approaching the design of web components. This is what gets me excited about web components.

Then I look at pretty much all the examples of web components out there and my nervousness kicks in. Hardly any of them spare a thought for backwards-compatibility. Take a look, for example, at the entire contents of the body element for the Polymer Shop demo site:

<shop-app unresolved="">SHOP</shop-app>

This seems really odd to me, because I don’t think it’s a good way to “sell” a technology.

Compare service workers to web components.

First of all, ask the question “who benefits from this technology?” In the case of service workers, it’s the end users. They get faster websites that handle network failure better. In the case of web components, there are no direct end-user benefits. Web components exist to make developers lives easier. That’s absolutely fine, but any developer convenience gained by the use of web components can’t come at the expense of the user—that price is too high.

The next question we usually ask when we’re evaluating a technology is “how well does it work?” Personally, I think it’s just as important to ask “how well does it fail?”

Service workers work well and fail well. If a browser supports service workers, the user gets all the benefits. If a browser doesn’t support service workers, the user get the same experience they would have always had.

Web components (will) work well, but fail badly. If a browser supports web components, the user gets the experience that the developer has crafted using these new technologies. If a browser doesn’t support web components, the user gets …probably nothing. It depends on how the web components have been designed.

It’s so much easier to get excited about implementing service workers. You’ve literally got nothing to lose and everything to gain. That’s not the case with web components. Or at least not with the way they are currently being sold.

See, this is why I think it’s so important to put some effort into designing web components that have some kind of fallback. Those web components will work well and fail well.

Look at the way new elements are designed for HTML. Think of complex additions like canvas, audio, video, and picture. Each one has been designed with backwards-compatibility in mind—there’s always a way to provide fallback content.

Web components give us developers the same power that, up until now, only belonged to browser makers. Web components also give us developers the same responsibilities as browser makers. We should take that responsibility seriously.

Web components are supposed to be the poster child for The Extensible Web Manifesto. I’m all for an extensible web. But the way that web components are currently being built looks more like an endorsement of The Replaceable Web Manifesto. I’m not okay with a replaceable web.

Here’s hoping that my concerns won’t be dismissed as “piffle and tosh” again by the very people who should be thinking about these issues.

Contrary to popular belief, web standards aren’t created by a shadowy cabal and then handed down to browser makers to implement. Quite the opposite. Browser makers come together in standards bodies and try to come to an agreement about how to collectively create and implement standards. That keeps them very busy. They don’t tend to get out very often, but when they do, the browser/standards makers have one message for developers: “We want to make your life better, so tell us what you want and that’s what we’ll work on!”

In practice, this turns out not to be the case.

Case in point: responsive images. For years, this was the number one feature that developers were crying out for. And yet, the standards bodies—and, therefore, browser makers—dragged their heels. First they denied that it was even a problem worth solving. Then they said it was simply too hard. Eventually, thanks to the herculean efforts of the Responsive Images Community Group, the browser makers finally began to work on what developers had been begging for.

Now that same community group is representing the majority of developers once again. Element queries—or container queries—have been top of the wish list of working devs for quite a while now. The response from browser makers is the same as it was for responsive images. They say it’s simply too hard.

Here’s a third example: web components. There are many moving parts to web components, but one of the most exciting to developers who care about accessibility and backwards-compatibility is the idea of extending existing elements:

It’s my opinion that, for as long as there is a dependence on JS for custom elements, we should extend existing elements when writing custom elements. It makes sense for developers, because new elements have access to properties and methods that have been defined and tested for many years; and it makes sense for users, as they have fallback in case of JS failure, and baked-in accessibility fundamentals.

So instead of having to create a whole new element from scratch like this:

<taco-button>Click me!</taco-button>

…you could piggy-back on an existing element like this:

<button is="taco-button">Click me!</button>

That way, you get the best of both worlds: the native semantics of button topped with all the enhancements you want to add with your taco-button custom element. Brilliant! Github is using this to extend the time element, for example.

I’m not wedded to the is syntax, but I do think it’s vital that there is some declarative mechanism to extend existing elements instead of creating every custom element from scratch each time.

Now it looks like that’s the bit of web components that isn’t going to make the cut. Why? Because browser makers say it’s simply too hard.

As Bruce points out, this is in direct conflict with the design principles that are supposed to be driving the creation and implementation of web standards.

It probably wouldn’t bother me so much except that browser makers still trot out the party line, “We want to hear what developers want!” Their actions demonstrate that this claim is somewhat hollow.

I don’t hold out much hope that we’ll get the ability to extend existing elements for web components. I think we can still find ways to piggy-back on existing semantics, but it’s going to take more work:

<taco-button><button>Click me!</button></taco-button>

That isn’t very elegant and I can foresee a lot of trickiness trying to sift the fallback content (the button tags) from the actual content (the “Click me!” text).

But I guess that’s what we’ll be stuck with. The alternative is simply too hard.

I’ve said it before, but I’m going to reiterate my conflicted feelings about Web Components:

I have conflicting feelings about Web Components. I am simultaneously very excited and very nervous.

There are broadly two ways that they could potentially be used:

1. Web Components are used by developers to incrementally add more powerful elements to their websites. This evolutionary approach feels very much in line with the thinking behind the extensible web manifesto. Or:
2. Web Components are used by developers as a monolithic platform, much like Angular or Ember is used today. The end user either gets everything or they get nothing.

The second scenario is a much more revolutionary approach—sweep aside the web that has come before, and usher in a new golden age of Web Components. Personally, I’m not comfortable with that kind of year-zero thinking. I prefer evolution over revolution:

Revolutions sometimes change the world to the better. Most often, however, it is better to evolve an existing design rather than throwing it away. This way, authors don’t have to learn new models and content will live longer. Specifically, this means that one should prefer to design features so that old content can take advantage of new features without having to make unrelated changes. And implementations should be able to add new features to existing code, rather than having to develop whole separate modes.

The evolutionary model is exemplified by the design of HTML 5.

The revolutionary model is exemplified by the design of XHTML 2.

I really hope that the Web Components model goes down the first route.

Up until recently, my inner Web Components pendulum was swinging towards the hopeful end of my spectrum of anticipation. That was mainly driven by the ability of custom elements to extend existing HTML elements.

So, for example, instead of creating a new element like this:

<taco-button>...</taco-button>

…you can piggyback off the existing semantics of the button element like this:

<button is="taco-button">...</button>

For a real-world example, see Github’s use of <time is="time-ago">.

I wrote about creating responsible Web Components:

That means we can use web components as a form of progressive enhancement, turbo-charging pre-existing elements instead of creating brand new elements from scratch. That way, we can easily provide fallback content for non-supporting browsers.

I’d like to propose that a fundamental principle of good web component design should be: “Where possible, extend an existing HTML element instead of creating a new element from scratch.”

Peter Gasston also has a great post on best practice for creating custom elements:

It’s my opinion that, for as long as there is a dependence on JS for custom elements, we should extend existing elements when writing custom elements. It makes sense for developers, because new elements have access to properties and methods that have been defined and tested for many years; and it makes sense for users, as they have fallback in case of JS failure, and baked-in accessibility fundamentals.

But now it looks like this superpower of custom elements is being nipped in the bud:

It also does not address subclassing normal elements. Again, while that seems desirable the current ideas are not attractive long term solutions. Punting on it in order to ship a v1 available everywhere seems preferable.

Now, I’m not particularly wedded to the syntax of using the is="" attribute to extend existing elements …but I do think that the ability to extend existing elements declaratively is vital. I’m not alone, although I may very well be in the minority.

Bruce has outlined some use cases and Steve Faulkner has enumerated the benefits of declarative extensibility:

I think being able to extend existing elements has potential value to developers far beyond accessibility (it just so happens that accessibility is helped a lot by re-use of existing HTML features.)

Bruce concurs:

Like Steve, I’ve no particularly affection (or enmity) towards the <input type="radio" is="luscious-radio"> syntax. But I’d like to know, if it’s dropped, how progressive enhancement can be achieved so we don’t lock out users of browsers that don’t have web components capabilities, JavaScript disabled or proxy browsers. If there is a concrete plan, please point me to it. If there isn’t, it’s irresponsible to drop a method that we can see working in the example above with nothing else to replace it.

He adds:

I also have a niggling worry that this may affect the uptake of web components.

I think he’s absolutely right. I think there are many developers out there in a similar position to me, uncertain exactly what to make of this new technology. I was looking forward to getting really stuck into Web Components and figuring out ways of creating powerful little extensions that I could start using now. But if Web Components turn out to be an all-or-nothing technology—a “platform”, if you will—then I will not only not be using them, I’ll be actively arguing against their use.

I really hope that doesn’t happen, but I must admit I’m not hopeful—my inner pendulum has swung firmly back towards the nervous end of my anticipation spectrum. That’s because I’m getting the distinct impression that the priorities being considered for Web Components are those of JavaScript framework creators, rather than web developers looking to add incremental improvements while maintaining backward compatibility.

If that’s the case, then Web Components will be made in the image of existing monolithic MVC frameworks that require JavaScript to do anything, even rendering content. To me, that’s a dystopian vision, one I can’t get behind.