Read the Tea Leaves Software and other dark arts, by Nolan Lawson

The end of the year is a good time for reflection, and this year I’m going to do something a bit different. I’d like to list some of the calls I’ve made over the years, and how well those predictions have turned out.

So without further ado, here’s a list of things I’ve been wrong about or right about over the years.

Quick links:

• Wrong: web workers will take over the world
• Wrong: Safari is the new IE
• Right: developer experience is trumping user experience
• Right: I’m better off without a Twitter account
• Right: the cost of small modules
• Mixed: progressive enhancement isn’t dead, but it smells funny

Wrong: web workers will take over the world

Around 2015, I got really excited by web workers. I gave talks, I wrote a blog post, and I wrote an app that got a fair amount of attention. Unfortunately it turned out web workers were not going to take over the world in the way I imagined.

My enthusiasm for web workers mostly came from my experience with Android development. In Android development, if you don’t want your app to be slow, you move work to a background thread. After I became a web developer, I discovered it was suddenly very hard to make apps that weren’t janky. Oh, the web browser only has one thread? Well, there’s your problem.

What I didn’t know at the time, though, was that browsers already had a lot of tricks for moving work off the main thread; they’re just not necessarily very obvious, or directly exposed to web developers. You can see my ignorance in this video, where I’m purportedly showing the performance advantages of my worker-powered Pokémon app by scrolling the screen on mobile Chrome.

As I learned later, though, scrolling runs off-main-thread in modern browsers (and more importantly, composited). So the only thing that’s going to make this scrolling smoother is to not block it with unnecessary touchstart/touchmove listeners, or for the Chrome team to improve their scrolling implementation (as in fact, they have been doing). There are also differences between subscrollers and main-document scrollers, as I learned later.

All of these things are non-obvious to web developers, because they’re not directly exposed in an API. So in my ignorance, I pointed to the one case where threading is exposed in a web API, i.e. web workers.

While it is true, though, that blocking the main thread is a major cause of slowdowns in web pages, web workers aren’t the panacea I imagined. The reasons are laid out very succinctly by Evan You in this talk, but to summarize his points: moving work from the main thread to a background worker is very difficult, and the payoff is not so great.

The main reason it’s difficult is that you always have to come back to the main thread to do work on the DOM anyway. This is what libraries like worker-dom do. Also, some APIs can only be invoked synchronously on the main thread, such as getBoundingClientRect. Furthermore, as pointed out by Pete Hunt, web workers cannot handle preventDefault or stopPropagation (e.g. in a click handler), because those must be handled synchronously.

So on the one hand, you can’t just take existing web code and port it to a web worker; there are some things that have to be tweaked, and other things that are just impossible. Then on the other hand, moving things to a worker creates its own costs. The cost of cloning data between threads can be expensive (note: to be fair, Chrome has improved their cloning performance since I wrote that post). There is also a built-in latency when sending messages between the two threads, so you don’t necessarily want to pay that round-trip cost for every interaction. Also, some work has to be done on the main thread anyway, and it’s not guaranteed that those costs are the small ones.

Since then, I’ve come to believe that the best way to avoid the cost of main thread work (such as virtual DOM diffing in a library like React) is not by moving it to a background thread, but rather by skipping it entirely. SvelteJS does this, as explained in this talk by Rich Harris. Also, you can use APIs like requestIdleCallback to delay work on the main thread. Future APIs like hasPendingUserInput may help as well.

Of course, I’m not saying that web workers should never be used. For long-running computations that don’t rely on the DOM, they’re definitely useful. And perhaps sometime in the future it will become more viable to run your “entire app” in a worker thread, as sketched out here by Jason Miller. APIs like SharedArrayBuffer, blöcks, and some kind of asynchronous preventDefault/stopPropagation may tip the balance in web workers’ favor. But for now I’ll say that I was wrong on this call.

Wrong: Safari is the new IE

“Safari is the new IE” is probably my most-read post of all time, since it got picked up by Ars Technica. Unfortunately I’ve learned a lot about how the browser industry works since I wrote it, and nowadays I regard it with a bit of embarrassment.

As it turns out, Safari is not really the new IE. At the time I wrote that post (2015), the WebKit team was dragging their feet a bit, but since then they’ve really picked up the pace. If you look at metrics like HTML5Test, CanIUse, or ES2015+ compatibility tables, you’ll see they’ve made a lot of progress since 2015. They’re still behind Chrome and Firefox, but they’re giving Edge a run for its money (although Edge is now switching to Chromium, so that’s less relevant).

Also, the WebKit team does a lot of work that is less obvious to web developers, but which they still deserve credit for. Safari is a beast when it comes to performance, and they often set the standard that other engines aim to beat. It’s no surprise that the Speedometer benchmark came from the WebKit team (with Safari originally winning), and quickly became a point of focus for Chrome, Edge, and Firefox. The MotionMark and JetStream benchmarks also originally came from WebKit.

The WebKit team also does some interesting privacy work, including intelligent tracking protection and double-keying of cross-origin storage. (I.e. if example.com stores data in an iframe inside of another website, that data will not be shared with example.com itself or other example.com iframes on other websites. This limits this ability of sites to do third-party tracking.)

To be clear, though, I don’t regret writing that blog post. It was a cry of anger from a guy who was tired of dealing with a lot of IndexedDB bugs, which the WebKit team eventually got around to fixing. Heck, I’ve been told that my blog post may have even motivated Apple to make those fixes, and to release excellent developer-facing features like Safari Technology Preview. So kudos, WebKit team: you proved me wrong!

In any case, it’s unlikely that we’ll ever have a situation like IE6 again, with one browser taking up 95% of all usage. The best contender for that title is currently Chrome, and although it ticks some of the IE6 boxes (outsized influence on the ecosystem, de-facto standardization of implementation details), it doesn’t tick some other ones (lack of investment from the company building it, falling behind on web standards). The state of browser diversity is certainly worrying, though, which makes it all the more important to support non-Chromium browsers like Safari and Firefox, and give them credit for the good work they’re doing.

So in that regard, I am sorry for creating a meme that still seems to stick to this day.

Right: developer experience is trumping user experience

This blog post didn’t get a lot of attention when I published it in early 2016, but I think I tapped into something that was happening in the web community: web developers were starting to focus on obscure developer-facing features of frontend frameworks rather than tangible benefits for end-users.

Since then, this point has been articulated particularly well by folks on the Chrome team and at Google, such as Malte Ubl (“Developer experience and user experience,” 2017) and Alex Russell (“The developer experience bait-and-switch,” 2018). Paul Lewis also touched on it a bit in late 2015 in “The cost of frameworks”.

Developer experience (DX) vs user experience (UX) is now a topic of hot debate among web developers, and although I may not have put my finger on the problem very well, I did start writing about it in early 2016. So I’ll chalk this up as something I was right about.

Right: I’m better off without a Twitter account

I deleted my Twitter account a little over a year ago, and I have no regrets about that.

Twitter has made some good moves in the past year, such as as bringing back the chronological timeline, but overall it’s still a cesspool of negativity, preening, and distractions. Also, I don’t believe any one company should have a monopoly on microblogging, so I’m putting my money where my mouth is by denying them my attention and ad revenue.

These days I use Mastodon and RSS, and I’m much happier. Mastodon in particular has served as a kind of nicotine patch for my Twitter addiction, and for that I’m grateful.

The fediverse does have some of the same negative characteristics as Twitter (brigading, self-righteousness, lack of nuance), but overall it’s much smaller and quieter than Twitter, and more importantly less addictive, so I use social media less these days than I used to. I tend to spend more time on my hobbies instead, one of which is (ironically) building a Mastodon client!

Right: the cost of small modules

“The cost of small modules” was one of my most-read posts of 2016, and in terms of the overall conclusions, I was right. JavaScript compilation and initial execution are expensive, as has been covered quite well by Addy Osmani in “The cost of JavaScript”.

Furthermore, a lot of the bloat was coming from the bundlers themselves. In the post, I identified Browserify and Webpack as the main offenders, with Closure Compiler and Rollup showing how to do it right. Since I wrote that post, though, Webpack and Browserify have stepped up their game, and now module concatenation is a standard practice for JavaScript bundlers.

One thing I didn’t understand at the time was why JavaScript compilation was so expensive for the “function-wrapping” format of bundlers like Webpack and Browserify. I only realized it later when researching some quirks about how JavaScript engines parse function bodies. The conclusions from that research were interesting, but the larger takeaway of “only include the code you need” was the important one.

Mixed: progressive enhancement isn’t dead, but it smells funny

For better or worse, progressive enhancement doesn’t seem to be doing very well these days. In retrospect, this blog post was more about Twitter shaming (see above for my thoughts on Twitter), but I think the larger point about progressive enhancement losing its cachet is right.

As we slowly enter a world where there is one major browser engine (Chromium), which is frequently updated and leading on web standards, supporting old or weird browsers just becomes less important. Developers have already voted with their feet to target mostly Chrome and Chrome derivatives, putting pressure on other browsers to either adopt Chromium themselves or else bleed users (and therefore relevance). It’s a self-perpetuating cycle – the less developers care about progressive enhancement, the less it matters.

I also believe the term “progressive enhancement” has been somewhat co-opted by the Chrome devrel team as as euphemism for giving the best experience to Chrome and a poorer experience to “older browsers” (aka non-Chrome browsers). It’s a brilliant re-branding that feeds into web developers’ deepest wish, which is to live in a Chrome-only world where they only have to focus on Chrome.

That’s not to say progressive enhancement is without its virtues. Insofar as it encourages people to actually think about accessibility, performance, and web standards, it’s a good thing. But these days it’s becoming less about “build with HTML, layer on CSS, sprinkle on JavaScript” and more about “support a slightly older version of Chrome, target the latest version of Chrome.”

The other point I made in that blog post, which was about JavaScript-heavy webapps being better for the “next billion” Internet users, may turn out to be wrong. I’m not sure. Static websites are certainly easier on the user’s battery, and with a Service Worker they can still have the benefits of offline capabilities.

Perhaps with the new Portals proposal, we won’t even need to build SPAs to have fancy transitions between pages. I have a hunch that SPAs are being overused these days, and that user experience is suffering as a consequence, but that’s another bet that will have to be evaluated at a later date.

Conclusions

So that’s all for my roundup of bad takes, good takes, and the stuff in between. Hope you found it interesting, and happy 2019!