Progressive enhancement

js;dr is JavaScript required; Didn’t Read.

Pages that are empty without JS: dead to history (archive-org), unreliable for search results (despite any search engine claims of JS support, check it yourself), and thus ignorable. No need to waste time reading or responding.

Also known as, if it’s not curlable, it’s not on the web.

Weekly Timber is a client of mine that provides logging services in central Wisconsin. For them, a fast website is vital. Their business is located in Waushara County, and like many rural stretches in the United States, network quality and reliability isn’t great.

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Wisconsin has farmland for days, but it also has plenty of forests. When you need a company that cuts logs, Google is probably your first stop. How fast a given logging company’s website is might be enough to get you looking elsewhere if you’re left waiting too long on a crappy network connection.

I initially didn’t believe a Service Worker was necessary for Weekly Timber’s website. After all, if things were plenty fast to start with, why complicate things? On the other hand, knowing that my client services not just Waushara County, but much of central Wisconsin, even a barebones Service Worker could be the kind of progressive enhancement that adds resilience in the places it might be needed most.

The first Service Worker I wrote for my client’s website—which I’ll refer to henceforth as the “standard” Service Worker—used three well-documented caching strategies:

1. Precache CSS and JavaScript assets for all pages when the Service Worker is installed when the window’s load event fires.
2. Serve static assets out of CacheStorage if available. If a static asset isn’t in CacheStorage, retrieve it from the network, then cache it for future visits.
3. For HTML assets, hit the network first and place the HTML response into CacheStorage. If the network is unavailable the next time the visitor arrives, serve the cached markup from CacheStorage.

These are neither new nor special strategies, but they provide two benefits:

• Offline capability, which is handy when network conditions are spotty.
• A performance boost for loading static assets.

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A better, faster Service Worker

The web loves itself some “innovation,” which is a word we equally love to throw around. To me, true innovation isn’t when we create new frameworks or patterns solely for the benefit of developers, but whether those inventions benefit people who end up using whatever it is we slap up on the web. The priority of constituencies is a thing we ought to respect. Users above all else, always.

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There are certainly other challenges, but it’ll be up to you to weigh the user-facing benefits versus the development costs. In my opinion, this approach has broad applicability in applications such as blogs, marketing websites, news websites, ecommerce, and other typical use cases.

All in all, though, it’s akin to the performance improvements and efficiency gains that you’d get from an SPA. Only the difference is that you’re not replacing time-tested navigation mechanisms and grappling with all the messiness that entails, but enhancing them. That’s the part I think is really important to consider in a world where client-side routing is all the rage.

We should also expect people to have problems accessing our application from time to time. For example, intermittent network connectivity or CDN availability could prevent some or all of our JavaScript from loading.

It’s tempting to write off support for older browsers as not worth the effort, or to dismiss network issues as temporary glitches that resolve themselves after a refresh. But often it’s trivially easy to build features in a way that’s gracefully resilient to these types of problems.

This resilient approach, commonly known as progressive enhancement, is the practice of delivering web interfaces such that the basic functionality is implemented in HTML and CSS, and tiered upgrades to that base experience are layered on top with CSS and JavaScript, progressively, when their underlying technologies are supported by the browser.

Stimulus is a JavaScript framework with modest ambitions. It doesn’t seek to take over your entire front-end—in fact, it’s not concerned with rendering HTML at all. Instead, it’s designed to augment your HTML with just enough behavior to make it shine. Stimulus pairs beautifully with Turbolinks to provide a complete solution for fast, compelling applications with a minimal amount of effort.

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Sprinkle your HTML with controller, target, and action attributes:

Write a compatible controller and watch Stimulus bring it to life:

Turbolinks® makes navigating your web application faster. Get the performance benefits of a single-page application without the added complexity of a client-side JavaScript framework. Use HTML to render your views on the server side and link to pages as usual. When you follow a link, Turbolinks automatically fetches the page, swaps in its <body>, and merges its <head>, all without incurring the cost of a full page load.

• Optimizes navigation automatically. No need to annotate links or specify which parts of the page should change.
• No server-side cooperation necessary. Respond with full HTML pages, not partial page fragments or JSON.
• Respects the web. The Back and Reload buttons work just as you’d expect. Search engine-friendly by design.
• Supports mobile apps. Adapters for iOS and Android let you build hybrid applications using native navigation controls.

The architecture astronauts who, for the past decade, have been selling us on the necessity of React, Redux, and megabytes of JS, cannot comprehend the possibility of building an email app in 2020 with server-rendered HTML 😴

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The effects are truly toxic. Last decade’s obsession with SPAs has poisoned the minds of even the brightest teachers in our industry.

Like, there’s no way this stuff can work offline, right?!

Briefly read up on how HEY is implemented. Is this a correct summary of the pros and cons of its [server]-centric approach?
– Pro: Works fast on older devices.
– Con: Can’t be used offline.

Progressive enhancement is at the heart of everything I do on the web. It’s the bedrock of my speaking and writing too. Whether I’m writing about JavaScript, Ajax, HTML, or service workers, it’s always through the lens of progressive enhancement. Sometimes I explicitly bang the drum, like with Resilient Web Design. Other times I don’t mention it by name at all, and instead talk only about its benefits.

I sometimes get asked to name some examples of sites that still offer their core functionality even when JavaScript fails. I usually mention Amazon.com, although that has other issues. But quite often I find that a lot of the examples I might mention are dismissed as not being “web apps” (whatever that means).

The pushback I get usually takes the form of “Well, that approach is fine for websites, but it wouldn’t work something like Gmail.”

It’s always Gmail. Which is odd. Because if you really wanted to flummox me with a product or service that defies progressive enhancement, I’d have a hard time with something like, say, a game (although it would be pretty cool to build a text adventure that’s progressively enhanced into a first-person shooter). But an email client? That would work.

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Can you build something that works just like Gmail without using any JavaScript? No. But that’s not what progressive enhancement is about. It’s about providing the core functionality (reading and writing emails) with the simplest possible technology (HTML) and then enhancing using more powerful technologies (like JavaScript).

Progressive enhancement isn’t about making a choice between using simpler more robust technologies or using more advanced features; it’s about using simpler more robust technologies and then using more advanced features. Have your cake and eat it.

Fortunately I no longer need to run this thought experiment to imagine what it would be like if something like Gmail were built with a progressive enhancement approach. That’s what HEY is.

Sam Stephenson describes the approach they took:

HEY’s UI is 100% HTML over the wire. We render plain-old HTML pages on the server and send them to your browser encoded as text/html. No JSON APIs, no GraphQL, no React—just form submissions and links.

If you think that sounds like the web of 25 years ago, you’re right! Except the HEY front-end stack progressively enhances the “classic web” to work like the “2020 web,” with all the fidelity you’d expect from a well-built SPA.

See? It’s not either resilient or modern—it’s resilient and modern. Have your cake and eat it.

And yet this supremely sensible approach is not considered “modern” web development:

The architecture astronauts who, for the past decade, have been selling us on the necessity of React, Redux, and megabytes of JS, cannot comprehend the possibility of building an email app in 2020 with server-rendered HTML.

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Their focus is very much on people above technology. They’ve taken a human-centric approach to their product and a human-centric approach to web development …because ultimately, that’s what progressive enhancement is.

In September of 2019, Zach Leatherman tweeted

Which has a better First Meaningful Paint time?

1. a raw 8.5MB HTML file with the full text of every single one of my 27,506 tweets
2. a client rendered React site with exactly one tweet on it

(Spoiler: @____lighthouse reports 8.5MB of HTML wins by about 200ms)

Take a moment to wrap your head around that.

It’s perceivably faster to load 8.5 megabytes of HTML than it is to load a single tweet with a client-side React app.

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Real companies can and do build apps with HTML first

The folks at Basecamp just released a new email product, Hey, that tries to address a lot of the stuff that people find frustrating about email.

Neither product is really my cup of tea, but what I find super interesting is how Hey is built.

It’s core is server-rendered HTML. Basecamp is a Ruby on Rails shop (their CTO created Rails). Almost every view in the app is created on a server.

Then, they sprinkle just a little vanilla JS on top to turn things up to 11.

Basecamp uses a project they open sourced called Turbolinks. This JavaScript plugin intercepts link clicks and progressively enhances a server-side app into a single-page app (or SPA) by fetching additional pages with Ajax and only replacing the stuff that needs updating.

By using this approach, if the JS fails or isn’t supported, the app still loads and works and gives people the full experience. It also means you don’t have to wait for the full JS package to load before you can start using the app.

You still get the benefits of faster page loading that SPAs sometimes give you, but you don’t have to maintain two code bases or do complicated server-to-client hand offs (“rehydration” as they call it in the React world).

JavaScript can be pretty brittle, so having a way to exclude browsers that don’t cut the mustard via CSS can be really useful, especially if you don’t want to serve them large amounts of CSS that they won’t properly understand. Since we can’t prevent loading a stylesheet via feature queries, the media attribute on a <link> element seems the next best thing. Andy Kirk has come up with a few combinations: