Tags: declarative

31

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Thursday, May 5th, 2022

Tim Brown: CSS forces

Some interesting thoughts from Tim here. What if CSS could “displace” design decisions from one area to another?

For example, a flexible line spacing value in one container could influence margins that surround the text block. That change in spaciousness may mean that nearby headings need size or spacing adjustments to stay feeling connected.

This feels like the complete opposite way that most people approach design systems—modular, componentised, and discrete—but very in-line with the way that CSS has been designed—interconnected, relational and cascading.

Wednesday, May 4th, 2022

Contextual Spacing For Intrinsic Web Design | Modern CSS Solutions

To complement her talk at Beyond Tellerrand, Stephanie goes through some of the powerful CSS features that enable intrinsic web design. These are all great tools for the declarative design approach I was talking about:

Tuesday, April 19th, 2022

Be the browser’s mentor, not its micromanager. - Build Excellent Websites

This one-page site that Andy has made to illustrate his talk at All Day Hey is exactly what I was talking about with declarative design.

Give the browser some solid rules and hints, then let it make the right decisions for the people that visit it, based on their device, connection quality and capabilities. This is how they will get a genuinely great user experience, rather than a fragmented, broken one.

Thursday, April 14th, 2022

Declarative design

I feel like in the past few years there’s been a number of web design approaches that share a similar mindset. Intrinsic web design by Jen; Every Layout by Andy and Heydon; Utopia by Trys and James.

To some extent, their strengths lie in technological advances in CSS: flexbox, grid, calc, and so on. But more importantly, they share an approach. They all focus on creating the right inputs rather than trying to control every possible output. Leave the final calculations for those outputs to the browser—that’s what computers are good at.

As Andy puts it:

Be the browser’s mentor, not its micromanager.

Reflecting on Utopia’s approach, Jim Nielsen wrote:

We say CSS is “declarative”, but the more and more I write breakpoints to accommodate all the different ways a design can change across the viewport spectrum, the more I feel like I’m writing imperative code. At what quantity does a set of declarative rules begin to look like imperative instructions?

In contrast, one of the principles of Utopia is to be declarative and “describe what is to be done rather than command how to do it”. This approach declares a set of rules such that you could pick any viewport width and, using a formula, derive what the type size and spacing would be at that size.

Declarative! Maybe that’s the word I’ve been looking for to describe the commonalities between Utopia, Every Layout, and intrinsic web design.

So if declarative design is a thing, does that also mean imperative design is also a thing? And what might the tools and technologies for imperative design look like?

I think that Tailwind might be a good example of an imperative design tool. It’s only about the specific outputs. Systematic thinking is actively discouraged; instead you say exactly what you want the final pixels on the screen to be.

I’m not saying that declarative tools—like Utopia—are right and that imperative tools—like Tailwind—are wrong. As always, it depends. In this case, it depends on the mindset you have.

If you agree with this statement, you should probably use an imperative design tool:

CSS is broken and I want my tools to work around the way CSS has been designed.

But if you agree with this statement, you should probably use a declarative design tool:

CSS is awesome and I want my tools to amplify the way that CSS had been designed.

If you agree with the first statement but you then try using a declarative tool like Utopia or Every Layout, you will probably have a bad time. You’ll probably hate it. You may declare the tool to be “bad”.

Likewise if you agree with the second statement but you then try using an imperative tool like Tailwind, you will probably have a bad time. You’ll probably hate it. You may declare the tool to be “bad”.

It all depends on whether the philosophy behind the tool matches your own philosophy. If those philosophies match up, then using the tool will be productive and that tool will act as an amplifier—a bicycle for the mind. But if the philosophy of the tool doesn’t match your own philosophy, then you will be fighting the tool at every step—it will slow you down.

Knowing that this spectrum exists between declarative tools and imperative tools can help you when you’re evaluating technology. You can assess whether a web design tool is being marketed on the premise that CSS is broken or on the premise that CSS is awesome.

I wonder whether your path into web design and development might also factor into which end of the spectrum you’d identify with. Like, if your background is in declarative languages like HTML and CSS, maybe intrisic web design really resonates. But if your background is in imperative languages like JavaScript, perhaps Tailwind makes more sense to you.

Again, there’s no right or wrong here. This is about matching the right tool to the right mindset.

Personally, the declarative design approach fits me like a glove. It feels like it’s in the tradition of John’s A Dao Of Web Design or Ethan’s Responsive Web Design—ways of working with the grain of the web.

Tuesday, April 12th, 2022

Thoughts on Exerting Control With Media Queries - Jim Nielsen’s Blog

Some thoughts on CSS, media queries, and fluid type prompted by Utopia:

We say CSS is “declarative”, but the more and more I write breakpoints to accommodate all the different ways a design can change across the viewport spectrum, the more I feel like I’m writing imperative code. At what quantity does a set of declarative rules begin to look like imperative instructions?

In contrast, one of the principles of Utopia is to be declarative and “describe what is to be done rather than command how to do it”. This approach declares a set of rules such that you could pick any viewport width and, using a formula, derive what the type size and spacing would be at that size.

Wednesday, March 9th, 2022

When should there be a declarative version of a JavaScript API?

I feel like it’s high time I revived some interest in my proposal for button type="share". Last I left it, I was gathering use cases and they seem to suggest that the most common use case for the Web Share API is sharing the URL of the current page.

If you want to catch up on the history of this proposal, here’s what I’ve previously written:

Remember, my proposal isn’t to replace the JavaScript API, it’s to complement it with a declarative option. The declarative option doesn’t need to be as fully featured as the JavaScript API, but it should be able to cover the majority use case. I think this should hold true of most APIs.

A good example is the Constraint Validation API. For the most common use cases, the required attribute and input types like “email”, “url”, and “number” have you covered. If you need more power, reach for the JavaScript API.

A bad example is the Geolocation API. The most common use case is getting the user’s current location. But there’s no input type="geolocation" (or button type="geolocation"). Your only choice is to use JavaScript. It feels heavy-handed.

I recently got an email from Taylor Hunt who has come up with a good litmus test for JavaScript APIs that should have a complementary declarative option:

I’ve been thinking about how a lot of recently-proposed APIs end up having to deal with what Chrome devrel’s been calling the “user gesture/activation budget”, and wondering if that’s a good indicator of when something should have been HTML in the first place.

I think he’s onto something here!

Think about any API that requires a user gesture. Often the documentation or demo literally shows you how to generate a button in JavaScript in order to add an event handler to it in order to use the API. Surely that’s an indication that a new button type could be minted?

The Web Share API is a classic example. You can’t invoke the API after an event like the page loading. You have to invoke the API after a user-initiated event like, oh, I don’t know …clicking on a button!

The Fullscreen API has the same restriction. You can’t make the browser go fullscreen unless you’re responding to user gesture, like a click. So why not have button type="fullscreen" in HTML to encapsulate that? And again, the fallback in non-supporting browsers is predictable—it behaves like a regular button—so this is trivial to polyfill. I should probably whip up a polyfill to demonstrate this.

I can’t find a list of all the JavaScript APIs that require a user gesture, but I know there’s more that I’m just not thinking of. I’d love to see if they’d all fit this pattern of being candidates for a new button type value.

The only potential flaw in this thinking is that some APIs that require a user gesture might also require a secure context (either being served over HTTPS or localhost). But as far as I know, HTML has never had the concept of features being restricted by context. An element is either supported or it isn’t.

That said, there is some prior art here. If you use input type="password" in a non-secure context—like a page being served over HTTP—the browser updates the interface to provide scary warnings. Perhaps browsers could do something similar for any new button types that complement secure-context JavaScript APIs.

Saturday, January 2nd, 2021

Loading and replacing HTML parts with HTML

I like this proposal for a declarative Ajax pattern. It’s relatively straightforward to polyfill, although backward-compatibility is an issue because of existing browser behaviour with the target attribute.

Tuesday, October 20th, 2020

Standards processing

I’ve been like a dog with a bone the way I’ve been pushing for a declarative option for the Web Share API in the shape of button type=“share”. It’s been an interesting window into the world of web standards.

The story so far…

That’s the situation currently. The general consensus seems to be that it’s probably too soon to be talking about implementation at this stage—the Web Share API itself is still pretty new—but gathering data to inform future work is good.

In planning for the next TPAC meeting (the big web standards gathering), Marcos summarised the situation like this:

Not blocking: but a proposal was made by @adactio to come up with a declarative solution, but at least two implementers have said that now is not the appropriate time to add such a thing to the spec (we need more implementation experience + and also to see how devs use the API) - but it would be great to see a proposal incubated at the WICG.

Now this where things can get a little confusing because it used to be that if you wanted to incubate a proposal, you’d have to do on Discourse, which is a steaming pile of crap that requires JavaScript in order to put text on a screen. But Šime pointed out that proposals can now be submitted on Github.

So that’s where I’ve submitted my proposal, linking through to the explainer document.

Like I said, I’m not expecting anything to happen anytime soon, but it would be really good to gather as much data as possible around existing usage of the Web Share API. If you’re using it, or you know anyone who’s using it, please, please, please take a moment to provide a quick description. And if you could help spread the word to get that issue in front of as many devs as possible, I’d be very grateful.

(Many thanks to everyone who’s already contributed to that issue—much appreciated!)

Monday, October 5th, 2020

The reason for a share button type

If you’re at all interested in what I wrote about a declarative Web Share API—and its sequel, a polyfill for button type=”share”—then you might be interested in an explainer document I’ve put together.

It’s a useful exercise for me to enumerate the reasoning for button type=“share” in one place. If you have any feedback, feel free to fork it or create an issue.

The document is based on my initial blog posts and the discussion that followed in this issue on the repo for the Web Share API. In that thread I got some pushback from Marcos. There are three points he makes. I think that two of them lack merit, but the third one is actually spot on.

Here’s the first bit of pushback:

Apart from placing a button in the content, I’m not sure what the proposal offers over what (at least one) browser already provides? For instance, Safari UI already provides a share button by default on every page

But that is addressed in the explainer document for the Web Share API itself:

The browser UI may not always be available, e.g., when a web app has been installed as a standalone/fullscreen app.

That’s exactly what I wanted to address. Browser UI is not always available and as progressive web apps become more popular, authors will need to provide a way for users to share the current URL—something that previously was handled by browsers.

That use-case of sharing the current page leads nicely into the second bit of pushback:

The API is specialized… using it to share the same page is kinda pointless.

But again, the explainer document for the Web Share API directly contradicts this:

Sharing the page’s own URL (a very common case)…

Rather than being a difference of opinion, this is something that could be resolved with data. I’d really like to find out how people are currently using the Web Share API. How much of the current usage falls into the category of “share the current page”? I don’t know the best way to gather this data though. If you have any ideas, let me know. I’ve started an issue where you can share how you’re using the Web Share API. Or if you’re not using the Web Share API, but you know someone who is, please let them know.

Okay, so those first two bits of pushback directly contradict what’s in the explainer document for the Web Share API. The third bit of pushback is more philosophical and, I think, more interesting.

The Web Share API explainer document does a good job of explaining why a declarative solution is desirable:

The link can be placed declaratively on the page, with no need for a JavaScript click event handler.

That’s also my justification for having a declarative alternative: it would be easier for more people to use. I said:

At a fundamental level, declarative technologies have a lower barrier to entry than imperative technologies.

But Marcos wrote:

That’s demonstrably false and a common misconception: See OWL, XForms, SVG, or any XML+namespace spec. Even HTML is poorly understood, but it just happens to have extremely robust error recovery (giving the illusion of it being easy). However, that’s not a function of it being “declarative”.

He’s absolutely right.

It’s not so much that I want a declarative option—I want an option that has robust error recovery. After all, XML is a declarative language but its error handling is as strict as an imperative language like JavaScript: make one syntactical error and nothing works. XML has a brittle error-handling model by design. HTML and CSS have extremely robust error recovery by design. It’s that error-handling model that gives HTML and CSS their robustness.

I’ve been using the word “declarative” when I actually meant “robust in handling errors”.

I guess that when I’ve been talking about “a declarative solution”, I’ve been thinking in terms of the three languages parsed by browsers: HTML, CSS, and JavaScript. Two of those languages are declarative, and those two also happen to have much more forgiving error-handling than the third language. That’s the important part—the error handling—not the fact that they’re declarative.

I’ve been using “declarative” as a shorthand for “either HTML or CSS”, but really I should try to be more precise in my language. The word “declarative” covers a wide range of possible languages, and not all of them lower the barrier to entry. A declarative language with a brittle error-handling model is as daunting as an imperative language.

I should try to use a more descriptive word than “declarative” when I’m describing HTML or CSS. Resilient? Robust?

With that in mind, button type=“share” is worth pursuing. Yes, it’s a declarative option for using the Web Share API, but more important, it’s a robust option for using the Web Share API.

I invite you to read the explainer document for a share button type and I welcome your feedback …especially if you’re currently using the Web Share API!

Thursday, October 1st, 2020

share-button-type/explainer.md

If you’ve been following my recent blog posts about a declarative option for the Web Share API, you might be interested in this explainer document I’ve put together. It outlines the use case for button type="share".

Thursday, September 24th, 2020

The failed promise of Web Components – Lea Verou

A spot-on summary of where we’ve ended up with web components.

Web Components had so much potential to empower HTML to do more, and make web development more accessible to non-programmers and easier for programmers.

But then…

Somewhere along the way, the space got flooded by JS frameworks aficionados, who revel in complex APIs, overengineered build processes and dependency graphs that look like the roots of a banyan tree.

Alas, that’s true. Lea wonders how this can be fixed:

I’m not sure if this is a design issue, or a documentation issue.

I worry that is a cultural issue.

Using a custom element from the directory often needs to be preceded by a ritual of npm flugelhorn, import clownshoes, build quux, all completely unapologetically because “here is my truckload of dependencies, yeah, what”.

Wednesday, September 16th, 2020

A polyfill for button type=”share”

After writing about a declarative Web Share API here yesterday I thought I’d better share the idea (see what I did there?).

I opened an issue on the Github repo for the spec.

(I hope that’s the right place for this proposal. I know that in the past ideas were kicked around on the Discourse site for Web platform Incubator Community Group but I can’t stand Discourse. It literally requires JavaScript to render anything to the screen even though the entire content is text. If it turns out that that is the place I should’ve posted, I guess I’ll hold my nose and do it using the most over-engineered reinvention of the browser I’ve ever seen. But I believe that the plan is for WICG to migrate proposals to Github anyway.)

I also realised that, as the JavaScript Web Share API already exists, I can use it to polyfill my suggestion for:

<button type="share">

The polyfill also demonstrates how feature detection could work. Here’s the code.

This polyfill takes an Inception approach to feature detection. There are three nested levels:

  1. This browser supports button type="share". Great! Don’t do anything. Otherwise proceed to level two.
  2. This browser supports the JavaScript Web Share API. Use that API to share the current page URL and title. Otherwise proceed to level three.
  3. Use a mailto: link to prefill an email with the page title as the subject and the URL in the body. Ya basic!

The idea is that, as long as you include the 20 lines of polyfill code, you could start using button type="share" in your pages today.

I’ve made a test page on Codepen. I’m just using plain text in the button but you could use a nice image or SVG or combination. You can use the Codepen test page to observe two of the three possible behaviours browsers could exhibit:

  1. A browser supports button type="share". Currently that’s none because I literally made this shit up yesterday.
  2. A browser supports the JavaScript Web Share API. This is Safari on Mac, Edge on Windows, Safari on iOS, and Chrome, Samsung Internet, and Firefox on Android.
  3. A browser supports neither button type="share" nor the existing JavaScript Web Share API. This is Firefox and Chrome on desktop (and Edge if you’re on a Mac).

See the Pen Polyfill for button type=”share" by Jeremy Keith (@adactio) on CodePen.

The polyfill doesn’t support Internet Explorer 11 or lower because it uses the DOM closest() method. Feel free to fork and rewrite if you need to support old IE.

Tuesday, September 15th, 2020

A declarative Web Share API

I’ve written about the Web Share API before. It’s a handy little bit of JavaScript that—if supported—brings up a system-level way of sharing a page. Seeing as it probably won’t be long before we won’t be able to see full URLs in browsers anymore, it’s going to fall on us as site owners to provide this kind of fundamental access.

Right now the Web Share API exists entirely in JavaScript. There are quite a few browser APIs like that, and it always feels like a bit of a shame to me. Ideally there should be a JavaScript API and a declarative option, even if the declarative option isn’t as powerful.

Take form validation. To cover the most common use cases, you probably only need to use declarative markup like input type="email" or the required attribute. But if your use case gets a bit more complicated, you can reach for the Constraint Validation API in JavaScript.

I like that pattern. I wish it were an option for JavaScript-only APIs. Take the Geolocation API, for example. Right now it’s only available through JavaScript. But what if there were an input type="geolocation" ? It wouldn’t cover all use cases, but it wouldn’t have to. For the simple case of getting someone’s location (like getting someone’s email or telephone number), it would do. For anything more complex than that, that’s what the JavaScript API is for.

I was reminded of this recently when Ada Rose Cannon tweeted:

It really feels like there should be a semantic version of the share API, like a mailto: link

I think she’s absolutely right. The Web Share API has one primary use case: let the user share the current page. If that use case could be met in a declarative way, then it would have a lower barrier to entry. And for anyone who needs to do something more complicated, that’s what the JavaScript API is for.

But Pete LePage asked:

How would you feature detect for it?

Good question. With the JavaScript API you can do feature detection—if the API isn’t supported you can either bail or provide your own implementation.

There a few different ways of extending HTML that allow you to provide a fallback for non-supporting browsers.

You could mint a new element with a content model that says “Browsers, if you do support this element, ignore everything inside the opening and closing tags.” That’s the way that the canvas element works. It’s the same for audio and video—they ignore everything inside them that isn’t a source element. So developers can provide a fallback within the opening and closing tags.

But forging a new element would be overkill for something like the Web Share API (or Geolocation). There are more subtle ways of extending HTML that I’ve already alluded to.

Making a new element is a lot of work. Making a new attribute could also be a lot of work. But making a new attribute value might hit the sweet spot. That’s why I suggested something like input type="geolocation" for the declarative version of the Geolocation API. There’s prior art here; this is how we got input types for email, url, tel, color, date, etc. The key piece of behaviour is that non-supporting browsers will treat any value they don’t understand as “text”.

I don’t think there should be input type="share". The action of sharing isn’t an input. But I do think we could find an existing HTML element with an attribute that currently accepts a list of possible values. Adding one more value to that list feels like an inexpensive move.

Here’s what I suggested:

<button type=”share” value=”title,text”>

For non-supporting browsers, it’s a regular button and needs polyfilling, no different to the situation with the JavaScript API. But if supported, no JS needed?

The type attribute of the button element currently accepts three possible values: “submit”, “reset”, or “button”. If you give it any other value, it will behave as though you gave it a type of “submit” or “button” (depending on whether it’s in a form or not) …just like an unknown type value on an input element will behave like “text”.

If a browser supports button type="share”, then when the user clicks on it, the browser can go “Right, I’m handing over to the operating system now.”

There’s still the question of how to pass data to the operating system on what gets shared. Currently the JavaScript API allows you to share any combination of URL, text, and description.

Initially I was thinking that the value attribute could be used to store this data in some kind of key/value pairing, but the more I think about it, the more I think that this aspect should remain the exclusive domain of the JavaScript API. The declarative version could grab the current URL and the value of the page’s title element and pass those along to the operating system. If you need anything more complex than that, use the JavaScript API.

So what I’m proposing is:

<button type="share">

That’s it.

But how would you test for browser support? The same way as you can currently test for supported input types. Make use of the fact that an element’s attribute value and an element’s property value (which 99% of the time are the same), will be different if the attribute value isn’t supported:

var testButton = document.createElement("button");
testButton.setAttribute("type","share");
if (testButton.type != "share") {
// polyfill
}

So that’s my modest proposal. Extend the list of possible values for the type attribute on the button element to include “share” (or something like that). In supporting browsers, it triggers a very bare-bones handover to the OS (the current URL and the current page title). In non-supporting browsers, it behaves like a button currently behaves.

Friday, March 20th, 2020

What Does `playsinline` Mean in Web Video? | CSS-Tricks

I have to admit, I don’t think I even knew of the existence of the playsinline attribute on the video element. Here, Chris runs through all the attributes you can put in there.

Sunday, July 21st, 2019

The Simplest Way to Load CSS Asynchronously | Filament Group, Inc.

Scott re-examines the browser support for loading everything-but-the-critical-CSS asynchronously and finds that it might now be as straightforward as this one declaration:

<link rel="stylesheet" href="/path/to/my.css" media="print" onload="this.media='all'">

I love the fact the Filament Group are actively looking at how deprecate their loadCSS polyfill—exactly the right attitude for polyfills in general.

Monday, June 10th, 2019

The CSS Mindset | Max Böck - Frontend Web Developer

This post absolutely nails what’s special about CSS …and why supersmart programmers might have trouble wrapping their head around it:

Other programming languages often work in controlled environments, like servers. They expect certain conditions to be true at all times, and can therefore be understood as concrete instructions as to how a program should execute.

CSS on the other hand works in a place that can never be fully controlled, so it has to be flexible by default.

Max goes on to encapsulate years of valuable CSS learnings into some short and snappy pieces of advices:

No matter what your level of CSS knowledge, this post has something for you—highly recommended!

Wednesday, March 13th, 2019

if statements and for loops in CSS - QuirksBlog

Personally, I find ppk’s comparison here to be spot on. I think that CSS can be explained in terms of programming concepts like if statements and for loops, if you squint at it just right.

This is something I’ve written about before.

Tuesday, February 26th, 2019

The CSS mental model - QuirksBlog

PPK looks at the different mental models behind CSS and JavaScript. One is declarative and one is imperative.

There’s a lot here that ties in with what I was talking about at New Adventures around the rule of least power in technology choice.

I’m not sure if I agree with describing CSS as being state-based. The example that illustrates this—a :hover style—feels like an exception rather than a typical example of CSS.

Monday, January 7th, 2019

A declarative router for service workers - JakeArchibald.com

An interesting proposal from Jake on a different way of defining how service worker fetch events could be handled under various conditions. For now, I have no particular opinion on it. I’m going to let this stew in my mind for a while.

Thursday, October 4th, 2018

Declaration

I like the robustness that comes with declarative languages. I also like the power that comes with imperative languages. Best of all, I like having the choice.

Take the video and audio elements, for example. If you want, you can embed a video or audio file into a web page using a straightforward declaration in HTML.

<audio src="..." controls><!-- fallback goes here --></audio>

Straightaway, that covers 80%-90% of use cases. But if you need to do more—like, provide your own custom controls—there’s a corresponding API that’s exposed in JavaScript. Using that API, you can do everything that you can do with the HTML element, and a whole lot more besides.

It’s a similar story with animation. CSS provides plenty of animation power, but it’s limited in the events that can trigger the animations. That’s okay. There’s a corresponding JavaScript API that gives you more power. Again, the CSS declarations cover 80%-90% of use cases, but for anyone in that 10%-20%, the web animation API is there to help.

Client-side form validation is another good example. For most us, the HTML attributes—required, type, etc.—are probably enough most of the time.

<input type="email" required />

When we need more fine-grained control, there’s a validation API available in JavaScript (yes, yes, I know that the API itself is problematic, but you get the point).

I really like this design pattern. Cover 80% of the use cases with a declarative solution in HTML, but also provide an imperative alternative in JavaScript that gives more power. HTML5 has plenty of examples of this pattern. But I feel like the history of web standards has a few missed opportunities too.

Geolocation is a good example of an unbalanced feature. If you want to use it, you must use JavaScript. There is no declarative alternative. This doesn’t exist:

<input type="geolocation" />

That’s a shame. Anyone writing a form that asks for the user’s location—in order to submit that information to a server for processing—must write some JavaScript. That’s okay, I guess, but it’s always going to be that bit more fragile and error-prone compared to markup.

(And just in case you’re thinking of the fallback—which would be for the input element to be rendered as though its type value were text—and you think it’s ludicrous to expect users with non-supporting browsers to enter latitude and longitude coordinates by hand, I direct your attention to input type="color": in non-supporting browsers, it’s rendered as input type="text" and users are expected to enter colour values by hand.)

Geolocation is an interesting use case because it only works on HTTPS. There are quite a few JavaScript APIs that quite rightly require a secure context—like service workers—but I can’t think of a single HTML element or attribute that requires HTTPS (although that will soon change if we don’t act to stop plans to create a two-tier web). But that can’t have been the thinking behind geolocation being JavaScript only; when geolocation first shipped, it was available over HTTP connections too.

Anyway, that’s just one example. Like I said, it’s not that I’m in favour of declarative solutions instead of imperative ones; I strongly favour the choice offered by providing declarative solutions as well as imperative ones.

In recent years there’s been a push to expose low-level browser features to developers. They’re inevitably exposed as JavaScript APIs. In most cases, that makes total sense. I can’t really imagine a declarative way of accessing the fetch or cache APIs, for example. But I think we should be careful that it doesn’t become the only way of exposing new browser features. I think that, wherever possible, the design pattern of exposing new features declaratively and imperatively offers the best of the both worlds—ease of use for the simple use cases, and power for the more complex use cases.

Previously, it was up to browser makers to think about these things. But now, with the advent of web components, we developers are gaining that same level of power and responsibility. So if you’re making a web component that you’re hoping other people will also use, maybe it’s worth keeping this design pattern in mind: allow authors to configure the functionality of the component using HTML attributes and JavaScript methods.