Journal tags: medium

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On this day

I’m in San Francisco to speak at An Event Apart, which kicks off tomorrow. But I arrived a few days early so that I could attend Indie Web Camp SF.

Yesterday was the discussion day. Most of the attendees were seasoned indie web campers, so quite a few of the discussions went deep on some of the building blocks. It was a good opportunity to step back and reappraise technology decisions.

Today is the day for making, tinkering, fiddling, and hacking. I had a few different ideas of what to do, mostly around showing additional context on my blog posts. I could, for instance, show related posts—other blog posts (or links) that have similar tags attached to them.

But I decided that a nice straightforward addition would be to show a kind of “on this day” context. After all, I’ve been writing blog posts here for eighteen years now; chances are that if I write a blog post on any given day, there will be something in the archives from that same day in previous years.

So that’s what I’ve done. I’ll be demoing it shortly here at Indie Web Camp, but you can see it in action now. If you look at the page for this blog post, you should see a section at the end with the heading “Previously on this day”. There you’ll see links to other posts I’ve written on December 8th in years gone by.

It’s quite a mixed bag. There’s a post about when I used to have a webcam from sixteen years ago. There’s a report from the Flash On The Beach conference from thirteen years ago (I wrote that post while I was in Berlin). And five years ago, I was writing about markup patterns for web components.

I don’t know if anyone other than me will find this feature interesting (but as it’s my website, I don’t really care). Personally, I find it fascinating to see how my writing has changed, both in terms of subject matter and tone.

Needless to say, the further back in time you go, the more chance there is that the links in my blog posts will no longer work. That’s a real shame. But then it’s a pleasant surprise when I find something that I linked to that is still online after all this time. And I can take comfort from the fact that if anyone has ever linked to anything I’ve written on my website, then those links still work.

Oh, Vienna!

Earlier this year I was in Düsseldorf for a triple bill of events:

  1. Indie Web Camp
  2. Beyond Tellerrand
  3. Accessibility Club

At Accessibility Club, I had the pleasure of seeing a great presentation from Manuel Matuzovic. Afterwards, a gaggle of us geeks went out for currywurst and beer. I got chatting with Manuel, who mentioned that he’s based in Vienna, where he organises a web meetup. I told him I’d love to come and speak at it sometime. He seemed very keen on the idea!

A few weeks later, I dropped him a line so he knew I was serious with my offer:

Hi Manuel,

Just wanted to drop a quick line to say how nice it was to hang out in Düsseldorf—albeit briefly.

I’d definitely be up for coming over to Vienna sometime for a meet up. Hope we can make that work sometime!

Cheers,

Jeremy

Manuel responded:

thank you for reaching out to me. Your timing couldn’t be better. :)

I was so excited that you showed interest in visiting Vienna that I thought about organising something that’s a little bit bigger than a meetup but smaller than a conference. 

I’m meeting today with my friend Max Böck to tell him about the idea and to ask him if he would want to help me organise a event.

Well, they did it. I just got back from the inaugural Web Clerks Community Conf in Vienna. It was a day full of excellent talks given to a very warm and appreciate audience.

The whole thing was livestreamed so you can catch up on the talks. I highly recommend watching Max’s talk on the indie web.

I had a really nice time hanging out with friends like Charlie, Rachel, Heydon, and my travelling companion, Remy. But it was equally great to meet new people, like the students who were volunteering and attending. I love having the chance to meet the next generation of people working on the web.

Accessibility on The Session revisited

Earlier this year, I wrote about an accessibility issue I was having on The Session. Specifically, it was an issue with Ajax and pagination. But I managed to sort it out, and the lesson was very clear:

As is so often the case, the issue was with me trying to be too clever with ARIA, and the solution was to ease up on adding so many ARIA attributes.

Well, fast forward to the past few weeks, when I was contacted by one of the screen-reader users on The Session. There was, once again, a problem with the Ajax pagination, specifically with VoiceOver on iOS. The first page of results were read out just fine, but subsequent pages were not only never announced, the content was completely unavailable. The first page of results would’ve been included in the initial HTML, but the subsequent pages of results are injected with JavaScript (if JavaScript is available—otherwise it’s regular full-page refreshes all the way).

This pagination pattern shows up all over the site: lists of what’s new, search results, and more. I turned on VoiceOver and I was able to reproduce the problem straight away.

I started pulling apart my JavaScript looking for the problem. Was it something to do with how I was handling focus? I just couldn’t figure it out. And other parts of the site that used Ajax didn’t seem to be having the same problem. I was mystified.

Finally, I tracked down the problem, and it wasn’t in the JavaScript at all.

Wherever the pagination pattern appears, there are “previous” and “next” links, marked up with the appropriate rel="prev" and rel="next" attributes. Well, apparently past me thought it would be clever to add some ARIA attributes in there too. My thinking must’ve been something like this:

  • Those links control the area of the page with the search results.
  • That area of the page has an ID of “results”.
  • I should add aria-controls="results" to those links.

That was the problem …which is kind of weird, because VoiceOver isn’t supposed to have any support for aria-controls. Anyway, once I removed that attribute from the links, everything worked just fine.

Just as the solution last time was to remove the aria-atomic attribute on the updated area, the solution this time was to remove the aria-controls attribute on the links that trigger the update. Maybe this time I’ll learn my lesson: don’t mess with ARIA attributes you don’t understand.

Rams

I’ve made a few trips to Germany recently. I was in Berlin last week for the always-excellent Beyond Tellerrand. Marc did a terrific job of curating an entertaining and thought-provoking line-up of speakers. He also made sure that those speakers—myself included—were very well taken care of.

I was also in Frankfurt last month. It was for an event, but for once, it wasn’t an event that involved me in any way. Jessica was there for the Frankfurt Book Fair. I was tagging along for the ride.

While Jessica was out at the sprawling exhibition hall on the edge of town, I was exploring downtown Frankfurt. One lunch time, I found myself wandering around the town’s charming indoor market hall.

While I was perusing the sausages on display, I noticed an older gentleman also inspecting the meat wares. He looked familiar. That’s when the part of my brain responsible for facial recognition said “That’s Dieter Rams.” A more rational part of my brain said “It can’t be!”, but it seemed that my pattern matching was indeed correct.

As he began to walk away, the more impulsive part of my brain shouted “Say something!”, and before my calmer nature could intervene, I was opening my mouth to speak.

I think I would’ve been tongue-tied enough introducing myself to someone of Dieter Rams’s legendary stature, but it was compounded by having to do it in a second language.

Entschulding Sie!”, I said (“Excuse me”). “Sind Sie Dieter Rams?” (“Are you Dieter Rams?”)

“Ja, bin ich”, he said (“Yes, I am”).

At this point, my brain realised that it had nothing further planned and it left me to my own devices. I stumbled through a sentence saying something about what a pleasure it was to see him. I might have even said something stupid along the lines of “I’m a web designer!”

Anyway, he smiled politely as I made an idiot of myself, and then I said goodbye, reiterating that it was a real treat for me to meet him.

After I walked outside, I began questioning reality. Did that really just happen? It felt utterly surreal.

Of course afterwards I thought of all the things I could’ve said. L’esprit de l’escalier. Or as the Germans put it, Treppenwitz.

I could’ve told him that I collect design principles, of which his are probably the most well-known.

I could’ve told him about the time that Clearleft went on a field trip to the Design Museum in London to see an exhibition of his work, and how annoyed I was by the signs saying “Do Not Touch” …in front of household objects that were literally designed to be touched!

I could’ve told him how much I enjoyed the documentary that Gary Hustwit made about him.

But I didn’t say any of those things. I just spouted some inanity, like the starstruck fanboy I am.

There’ll be a lunchtime showing of the Rams documentary at An Event Apart in San Francisco, where I’ll be speaking in a few weeks. Now I wonder if rewatching it is just going to make me cringe as I’m reminded of my encounter in Frankfurt.

But I’m still glad I said something.

Mental models

I’ve found that the older I get, the less I care about looking stupid. This is remarkably freeing. I no longer have any hesitancy about raising my hand in a meeting to ask “What’s that acronym you just mentioned?” This sometimes has the added benefit of clarifying something for others in the room who might have been to shy to ask.

I remember a few years back being really confused about npm. Fortunately, someone who was working at npm at the time came to Brighton for FFConf, so I asked them to explain it to me.

As I understood it, npm was intended to be used for managing packages of code for Node. Wasn’t it actually called “Node Package Manager” at one point, or did I imagine that?

Anyway, the mental model I had of npm was: npm is to Node as PEAR is to PHP. A central repository of open source code projects that you could easily add to your codebase …for your server-side code.

But then I saw people talking about using npm to manage client-side JavaScript. That really confused me. That’s why I was asking for clarification.

It turns out that my confusion was somewhat warranted. The npm project had indeed started life as a repo for server-side code but had since expanded to encompass client-side code too.

I understand how it happened, but it confirmed a worrying trend I had noticed. Developers were writing front-end code as though it were back-end code.

On the one hand, that makes total sense when you consider that the code is literally in the same programming language: JavaScript.

On the other hand, it makes no sense at all! If your code’s run-time is on the server, then the size of the codebase doesn’t matter that much. Whether it’s hundreds or thousands of lines of code, the execution happens more or less independentally of the network. But that’s not how front-end development works. Every byte matters. The more code you write that needs to be executed on the user’s device, the worse the experience is for that user. You need to limit how much you’re using the network. That means leaning on what the browser gives you by default (that’s your run-time environment) and keeping your code as lean as possible.

Dave echoes my concerns in his end-of-the-year piece called The Kind of Development I Like:

I now think about npm and wonder if it’s somewhat responsible for some of the pain points of modern web development today. Fact is, npm is a server-side technology that we’ve co-opted on the client and I think we’re feeling those repercussions in the browser.

Writing back-end and writing front-end code require very different approaches, in my opinion. But those differences have been erased in “modern” JavaScript.

The Unix Philosophy encourages us to write small micro libraries that do one thing and do it well. The Node.js Ecosystem did this in spades. This works great on the server where importing a small file has a very small cost. On the client, however, this has enormous costs.

In a funny way, this situation reminds me of something I saw happening over twenty years ago. Print designers were starting to do web design. They had a wealth of experience and knowledge around colour theory, typography, hierarchy and contrast. That was all very valuable to bring to the world of the web. But the web also has fundamental differences to print design. In print, you can use as many typefaces as you want, whereas on the web, to this day, you need to be judicious in the range of fonts you use. But in print, you might have to limit your colour palette for cost reasons (depending on the printing process), whereas on the web, colours are basically free. And then there’s the biggest difference of all: working within known dimensions of a fixed page in print compared to working within the unknowable dimensions of flexible viewports on the web.

Fast forward to today and we’ve got a lot of Computer Science graduates moving into front-end development. They’re bringing with them a treasure trove of experience in writing robust scalable code. But web browsers aren’t like web servers. If your back-end code is getting so big that it’s starting to run noticably slowly, you can throw more computing power at it by scaling up your server. That’s not an option on the front-end where you don’t really have one run-time environment—your end users have their own run-time environment with its own constraints around computing power and network connectivity.

That’s a very, very challenging world to get your head around. The safer option is to stick to the mental model you’re familiar with, whether you’re a print designer or a Computer Science graduate. But that does a disservice to end users who are relying on you to deliver a good experience on the World Wide Web.

Third party

The web turned 30 this year. When I was back at CERN to mark this anniversary, there was a lot of introspection and questioning the direction that the web has taken. Everyone I know that uses the web is in agreement that tracking and surveillance are out of control. It seems only right to question whether the web has lost its way.

But here’s the thing: the technologies that enable tracking and surveillance didn’t exist in the early years of the web—JavaScript and cookies.

Without cookies, the web was stateless. This was by design. Now, I totally understand why cookies—or something like cookies—were needed. Without some way of keeping track of state, there’s no good way for a website to “remember” what’s in your shopping cart, or whether you’ve authenticated yourself.

But why would cookies ever need to work across domains? Authentication, shopping carts and all that good stuff can happen on the same domain. Third-party cookies, on the other hand, seem custom made for tracking and frankly, not much else.

Browsers allow you to disable third-party cookies, though it’s not yet the default. If enough people do it—and complain about the sites that stop working when third-party cookies are disabled—then maybe it can become the default.

Firefox is taking steps in this direction, automatically disabling some third-party cookies—the ones that known trackers. Safari is also taking steps to prevent cross-site tracking. It’s not too late to change the tide of third-party cookies.

Then there’s third-party JavaScript.

In retrospect, it seems unbelievable that third-party JavaScript is even possible. I mean, putting arbitrary code—that can then inject even more arbitrary code—onto your website? That seems like a security nightmare!

I imagine if JavaScript were being specced today, it would almost certainly be restricted to the same origin by default. But I guess the precedent had been set with images and style sheets: they could be embedded regardless of whether their domain names matched yours. Still, this is executable code we’re talking about here: that’s quite a footgun that the web has given site owners. And boy, oh boy, has it been used by the worst people to do the most damage.

Again, as with cookies, if we were to imagine what the web would be like if JavaScript was restricted by a same-domain policy, there are certainly things that would be trickier to do.

  • Embedding video, audio, and maps would get a lot finickier.
  • Analytics would need to be self-hosted. I don’t think that would bother any site owners. An analytics platform like Google Analytics that tracks people across domains is doing it for its own benefit rather than that of site owners.
  • Advertising wouldn’t be creepy and annoying. Instead of what’s so euphemistically called “personalisation”, advertisers would have to rely on serving relevant ads based on the content of the site rather than an invasive psychological profile of the user. (I honestly think that advertisers would benefit from this kind of targetting.)

It’s harder to imagine putting the genie back in the bottle when it comes to third-party JavaScript than it is with third-party cookies. All the same, I wish that browsers made it easier to experiment with it. Just as I can choose to accept all cookies, reject all cookies, or only accept same-origin cookies, I wish I could accept all JavaScript, reject all JavaScript, or only accept same-origin JavaScript.

As it is, browsers are making it harder and harder to exercise any control over JavaScript at all. So we reach for third-party tools. We don’t call them JavaScript managers though. We call them ad blockers. But honestly, most of the ad-blocker users I know—myself included—are not bothered by the advertising; we’re bothered by the tracking. We should really call them surveillance blockers.

If third-party JavaScript weren’t the norm, not only would it make the web more secure, it would make it way more performant. Read the chapter on third parties in this year’s newly-released Web Almanac. The figures are staggering.

93% of pages include at least one third-party resource, 76% of pages issue a request to an analytics domain, the median page requests content from at least 9 unique third-party domains that represent 35% of their total network activity, and the most active 10% of pages issue a whopping 175 third-party requests or more.

I don’t think all the web’s performance ills are due to third-party scripts; developers are doing a bang-up job of making their sites big and bloated with their own self-hosted frameworks and code. But as long as third-party JavaScript is allowed onto a site, there’s a limit to how much good developers can do to improve the performance of their sites.

I go to performance-related conferences and you know who I’ve never seen at those events? The people who write the JavaScript for third-party tracking scripts. Those developers are wielding an outsized influence on the health of the web.

I’m very happy to see the work being done by Mozilla and Apple to normalise the idea of rejecting third-party cookies. I’d love to see the rejection of third-party JavaScript normalised in the same way. I know that it would make my life as a developer harder. But that’s of lesser importance. It would be better for the web.

CSS for all

There have been some great new CSS properties and values shipping in Firefox recently.

Miriam Suzanne explains the difference between the newer revert value and the older inherit, initial and unset values in a video on the Mozilla Developer channel:

display: revert;

In another video, Jen describes some new properties for styling underlines (on links, for example):

text-decoration-thickness:  0.1em;
text-decoration-color: red;
text-underline-offset: 0.2em;
text-decoration-skip-ink: auto;

Great stuff!

As far as I can tell, all of these properties are available to you regardless of whether you are serving your website over HTTP or over HTTPS. That may seem like an odd observation to make, but I invite you to cast your mind back to January 2018. That’s when the Mozilla Security Blog posted about moving to secure contexts everywhere:

Effective immediately, all new features that are web-exposed are to be restricted to secure contexts. Web-exposed means that the feature is observable from a web page or server, whether through JavaScript, CSS, HTTP, media formats, etc. A feature can be anything from an extension of an existing IDL-defined object, a new CSS property, a new HTTP response header, to bigger features such as WebVR.

(emphasis mine)

Buzz Lightyear says to Woody: Secure contexts …secure contexts everywhere!

Despite that “effective immediately” clause, I haven’t observed any of the new CSS properties added in the past two years to be restricted to HTTPS. I’m glad about that. I wrote about this announcement at the time:

I am in total agreement that we should be encouraging everyone to switch to HTTPS. But requiring HTTPS in order to use CSS? The ends don’t justify the means.

If there were valid security reasons for making HTTPS a requirement, I would be all for enforcing this. But these are two totally separate areas. Enforcing HTTPS by withholding CSS support is no different to enforcing AMP by withholding search placement.

There’s no official word from the Mozilla Security Blog about any change to their two-year old “effective immediately” policy, and the original blog post hasn’t been updated. Maybe we can all just pretend it never happened.

FF Conf 2019

Friday was FF Conf day here in Brighton. This was the eleventh(!) time that Remy and Julie have put on the event. It was, as ever, excellent.

It’s a conference that ticks all the boxes for me. For starters, it’s a single-track event. The more I attend conferences, the more convinced I am that multi-track events are a terrible waste of time for attendees (and a financially bad model for organisers). I know that sounds like a sweeping broad generalisation, but ask me about it next time we meet and I’ll go into more detail. For now, I just want to talk about this mercifully single-track conference.

FF Conf has built up a rock-solid reputation over the years. I think that’s down to how Remy curates it. He thinks about what he wants to know and learn more about, and then thinks about who to invite to speak on those topics. So every year is like a snapshot of Remy’s brain. By happy coincidence, a snapshot of Remy’s brain right now looks a lot like my own.

You could tell that Remy had grouped the talks together in themes. There was a performance-themed chunk right after lunch. There was a people-themed chunk in the morning. There was a creative-coding chunk at the end of the day. Nice work, DJ.

I think it was quite telling what wasn’t on the line-up. There were no talks about specific libraries or frameworks. For me, that was a blessed relief. The only technology-specific talk was Alice’s excellent talk on Git—a tool that’s useful no matter what you’re coding.

One of the reasons why I enjoyed the framework-free nature of the day is that most talks—and conferences—that revolve around libraries and frameworks are invariably focused on the developer experience. Think about it: next time you’re watching a talk about a framework or library, ask yourself how it impacts user experience.

At FF Conf, the focus was firmly on people. In the case of Laura’s barnstorming presentation, those people are end users (I’m constantly impressed by how calm and measured Laura remains even when talking about blood-boilingly bad behaviour from the tech industry). In the case of Amina’s talk, the people are junior developers. And for Sharon’s presentation, the people are everyone.

One of the most useful talks of the day was from Anna who took us on a guided tour of dev tools to identify performance improvements. I found it inspiring in a very literal sense—if I had my laptop with me, I think I would’ve opened it up there and then and started tinkering with my websites.

Harry also talked about performance, but at Remy’s request, it was more business focused. Specifically, it was focused on Harry’s consultancy business. I think this would’ve been the perfect talk for more of an “industry” event, whereas FF Conf is very much a community event: Harry’s semi-serious jibes about keeping his performance secrets under wraps didn’t quite match the generous tone of the rest of the line-up.

The final two talks from Charlotte and Suz were a perfect double whammy.

When I saw Charlotte speak at Material in Iceland last year, I wrote this aside in my blog post summary:

(Oh, and Remy, when you start to put together the line-up for next year’s FF Conf, be sure to check out Charlotte Dann—her talk at Material was the perfect mix of code and creativity.)

I don’t think I can take credit for Charlotte being on the line-up, but I will take credit for saying she’d be the perfect fit.

And then Suz Hinton closed out the conference with this rallying cry that resonated perfectly with Laura’s talk:

Less mass-produced surveillance bullshit and more Harry Potter magic (please)!

I think that rallying cry could apply equally well to conferences, and I think FF Conf is a good example of that ethos in action.

Cat encounters

The latest episode of Ariel’s excellent Offworld video series (and podcast) is all about Close Encounters Of The Third Kind.

I have such fondness for this film. It’s one of those films that I love to watch on a Sunday afternoon (though that’s true of so many Spielberg films—Jaws, Raiders Of The Lost Ark, E.T.). I remember seeing it in the cinema—this would’ve been the special edition re-release—and feeling the seat under me quake with the rumbling of the musical exchange during the film’s climax.

Ariel invited Rose Eveleth and Laura Welcher on to discuss the film. They spent a lot of time discussing the depiction of first contact communication—Arrival being the other landmark film on this topic.

This is a timely discussion. There’s a new book by Daniel Oberhaus published by MIT Press called Extraterrestrial Languages:

If we send a message into space, will extraterrestrial beings receive it? Will they understand?

You can a read an article by the author on The Guardian, where he mentions some of the wilder ideas about transmitting signals to aliens:

Minsky, widely regarded as the father of AI, suggested it would be best to send a cat as our extraterrestrial delegate.

Don’t worry. Marvin Minsky wasn’t talking about sending a real live cat. Rather, we transmit instructions for building a computer and then we can transmit information as software. Software about, say, cats.

It’s not that far removed from what happened with the Voyager golden record, although that relied on analogue technology—the phonograph—and sent the message pre-compiled on hardware; a much slower transmission rate than radio.

But it’s interesting to me that Minsky specifically mentioned cats. There’s another long-term communication puzzle that has a cat connection.

The Yukka Mountain nuclear waste repository is supposed to store nuclear waste for 10,000 years. How do we warn our descendants to stay away? We can’t use language. We probably can’t even use symbols; they’re too culturally specific. A think tank called the Human Interference Task Force was convened to agree on the message to be conveyed:

This place is a message… and part of a system of messages… pay attention to it! Sending this message was important to us. We considered ourselves to be a powerful culture.

This place is not a place of honor…no highly esteemed deed is commemorated here… nothing valued is here.

What is here is dangerous and repulsive to us. This message is a warning about danger.

A series of thorn-like threatening earthworks was deemed the most feasible solution. But there was another proposal that took a two pronged approach with genetics and folklore:

  1. Breed cats that change colour in the presence of radioactive material.
  2. Teach children nursery rhymes about staying away from cats that change colour.

This is the raycat solution.

Near miss

When I was travelling across the Atlantic ocean on the Queen Mary 2 back in August, I had the pleasure of attending a series of on-board lectures by Charles Barclay from the Royal Astronomical Society.

One of those presentations was on the threat of asteroid impacts—always a fun topic! Charles mentioned Spaceguard, the group that tracks near-Earth objects.

Spaceguard is a pretty cool-sounding name for any organisation. The name comes from a work of (science) fiction. In Arthur C. Clarke’s 1973 book Rendezvous with Rama, Spaceguard is the name of a fictional organisation formed after a devastating asteroid impact on northen Italy—an event which is coincidentally depicted as happening on September 11th. That’s not a spoiler, by the way. The impact happens on the first page of the book.

At 0946 GMT on the morning of September 11 in the exceptionally beautiful summer of the year 2077, most of the inhabitants of Europe saw a dazzling fireball appear in the eastern sky.  Within seconds it was brighter than the Sun, and as it moved across the heavens—at first in utter silence—it left behind it a churning column of dust and smoke.

Somewhere above Austria it began to disintegrate, producing a series of concussions so violent that more than a million people had their hearing permanently damaged.  They were the lucky ones.

Moving at fifty kilometers a second, a thousand tons of rock and metal impacted on the plains of northern Italy, destroying in a few flaming moments the labor of centuries.

Later in the same lecture, Charles talked about the Torino scale, which is used to classify the likelihood and severity of impacts. Number 10 on the Torino scale means an impact is certain and that it will be an extinction level event.

Torino—Turin—is in northern Italy. “Wait a minute!”, I thought to myself. “Is this something that’s also named for that opening chapter of Rendezvous with Rama?”

I spoke to Charles about it afterwards, hoping that he might know. But he said, “Oh, I just assumed that a group of scientists got together in Turin when they came up with the scale.”

Being at sea, there was no way to easily verify or disprove the origin story of the Torino scale. Looking something up on the internet would have been prohibitively slow and expensive. So I had to wait until we docked in New York.

On our first morning in the city, Jessica and I popped into a bookstore. I picked up a copy of Rendezvous with Rama and re-read the details of that opening impact on northern Italy. Padua, Venice and Verona are named, but there’s no mention of Turin.

Sure enough, when I checked Wikipedia, the history and naming of the Torino scale was exactly what Charles Barclay surmised:

A revised version of the “Hazard Index” was presented at a June 1999 international conference on NEOs held in Torino (Turin), Italy. The conference participants voted to adopt the revised version, where the bestowed name “Torino Scale” recognizes the spirit of international cooperation displayed at that conference toward research efforts to understand the hazards posed by NEOs.

Indy maps

Remember when I wrote about adding travel maps to my site at the recent Indie Web Camp Brighton? I must confess that the last line I wrote was an attempt to catch a fish from the river of the lazy web:

It’s a shame that I can’t use the lovely Stamen watercolour tiles for these static maps though.

In the spirit of Cunningham’s Law, I was hoping that somebody was going to respond with “It’s totally possible to use Stamen’s watercolour tiles for static maps, dumbass—look!” (to which my response would have been “thank you very much!”).

Alas, no such response was forthcoming. The hoped-for schooling never forthcame.

Still, I couldn’t quite let go of the idea of using those lovely watercolour maps somewhere on my site. But I had decided that dynamic maps would have been overkill for my archive pages:

Sure, it looked good, but displaying the map required requests for a script, a style sheet, and multiple map tiles.

Then I had a thought. What if I keep the static maps on my archive pages, but make them clickable? Then, on the other end of that link, I can have the dynamic version. In other words, what if I had a separate URL just for the dynamic maps?

These seemed like a good plan to me, so while I was travelling by Eurostar—the only way to travel—back from the lovely city of Antwerp where I had been speaking at Full Stack Europe, I started hacking away on making the dynamic maps even more dynamic. After all, now that they were going to have their own pages, I could go all out with any fancy features I wanted.

I kept coming back to my original goal:

I was looking for something more like the maps in Indiana Jones films—a line drawn from place to place to show the movement over time.

I found a plug-in for Leaflet.js that animates polylines—thanks, Iván! With a bit of wrangling, I was able to get it to animate between the lat/lon points of whichever archive section the map was in. Rather than have it play out automatically, I also added a control so that you can start and stop the animation. While I was at it, I decided to make that “play/pause” button do something else too. Ahem.

If you’d like to see the maps in action, click the “play” button on any of these maps:

You get the idea. It’s all very silly really. It’s right up there with the time I made my sparklines playable. But that’s kind of the point. It’s my website so I can do whatever I want with it, no matter how silly.

First of all, the research department for adactio.com (that’s me) came up with the idea. Then that had to be sold in to upper management (that’s me too). A team was spun up to handle design and development (consisting of me and me). Finally, the finished result went live thanks to the tireless efforts of the adactio.com ops group (that would be me). Any feedback should be directed at the marketing department (no idea who that is).

Periodic background sync

Yesterday I wrote about how much I’d like to see silent push for the web:

I’d really like silent push for the web—the ability to update a cache with fresh content as soon as it’s published; that would be nifty! At the same time, I understand the concerns. It feels more powerful than other permission-based APIs like notifications.

Today, John Holt Ripley responded on Twitter:

hi there, just read your blog post about Silent Push for acthe web, and wondering if Periodic Background Sync would cover a few of those use cases?

Periodic background sync looks very interesting indeed!

It’s not the same as silent push. As the name suggests, this is about your service worker waking up periodically and potentially fetching (and caching) fresh content from the network. So the service worker is polling rather than receiving a push. But I’ll take it! It’s definitely close enough for the kind of use-cases I’ve been thinking about.

Interestingly, periodic background sync also ties into the other part of what I was writing about: permissions. I mentioned that adding a site the home screen could be interpreted as a signal to potentially allow more permissions (or at least allow prompts for more permissions).

Well, Chromium has a document outlining metrics for attempting to gauge site engagement. There’s some good thinking in there.

Silent push for the web

After Indie Web Camp in Berlin last year, I wrote about Seb’s nifty demo of push without notifications:

While I’m very unwilling to grant permission to be interrupted by intrusive notifications, I’d be more than willing to grant permission to allow a website to silently cache timely content in the background. It would be a more calm technology.

Phil Nash left a comment on the Medium copy of my post explaining that Seb’s demo of using the Push API without showing a notification wouldn’t work for long:

The browsers allow a certain number of mistakes(?) before they start to show a generic notification to say that your site sent a push notification without showing a notification. I believe that after ~10 or so notifications, and that’s different between browsers, they run out of patience.

He also provided me with the name to describe what I’m after:

You’re looking for “silent push” as are many others.

Silent push is something that is possible in native apps. It isn’t (yet?) available on the web, presumably because of security concerns.

It’s an API that would ripe for abuse. I mean, just look at the mess we’ve made with APIs like notifications and geolocation. Sure, they require explicit user opt-in, but these opt-ins are seen so often that users are sick of seeing them. Silent push would be one more permission-based API to add to the stack of annoyances.

Still, I’d really like silent push for the web—the ability to update a cache with fresh content as soon as it’s published; that would be nifty! At the same time, I understand the concerns. It feels more powerful than other permission-based APIs like notifications.

Maybe there could be another layer of permissions. What if adding a site to your home screen was the first step? If a site is running on HTTPS, has a service worker, has a web app manifest, and has been added to the homescreen, maybe then and only then should it be allowed to prompt for permission to do silent push.

In other words, what if certain very powerful APIs were only available to progressive web apps that have successfully been added to the home screen?

Frankly, I’d be happy if the same permissions model applied to web notifications too, but I guess that ship has sailed.

Anyway, all this is pure conjecture on my part. As far as I know, silent push isn’t on the roadmap for any of the browser vendors right now. That’s fair enough. Although it does annoy me that native apps have this capability that web sites don’t.

It used to be that there was a long list of features that only native apps could do, but that list has grown shorter and shorter. The web’s hare is catching up to native’s tortoise.

Indy web

It was Indie Web Camp Brighton on the weekend. After a day of thought-provoking discussions, I thoroughly enjoyed spending the second day tinkering on my website.

For a while now, I’ve wanted to add maps to my monthly archive pages (to accompany the calendar heatmaps I added at a previous Indie Web Camp). Whenever I post anything to my site—a blog post, a note, a link—it’s timestamped and geotagged. I thought it would be fun to expose that in a glanceable way. A map seems like the right medium for that, but I wanted to avoid the obvious route of dropping a load of pins on a map. Instead I was looking for something more like the maps in Indiana Jones films—a line drawn from place to place to show the movement over time.

I talked to Aaron about this and his advice was that a client-side JavaScript embedded map would be the easiest option. But that seemed like overkill to me. This map didn’t need to be pannable or zoomable; just glanceable. So I decided to see if how far I could get with a static map. I timeboxed two hours for it.

After two hours, I admitted defeat.

I was able to find the kind of static maps I wanted from Mapbox—I’m already using them for my check-ins. I could even add a polyline, which is exactly what I wanted. But instead of passing latitude and longitude co-ordinates for the points on the polyline, the docs explain that I needed to provide …cur ominous thunder and lightning… The Encoded Polyline Algorithm Format.

Go to that link. I’ll wait.

Did you read through the eleven steps of instructions? Did you also think it was a piss take?

  1. Take the initial signed value.
  2. Multiply it by 1e5.
  3. Convert that decimal value to binary.
  4. Left-shift the binary value one bit.
  5. If the original decimal value is negative, invert this encoding.
  6. Break the binary value out into 5-bit chunks.
  7. Place the 5-bit chunks into reverse order.
  8. OR each value with 0x20 if another bit chunk follows.
  9. Convert each value to decimal.
  10. Add 63 to each value.
  11. Convert each value to its ASCII equivalent.

This was way beyond my brain’s pay grade. But surely someone else had written the code I needed? I did some Duck Duck Going and found a piece of PHP code to do the encoding. It didn’t work. I Ducked Ducked and Went some more. I found a different piece of PHP code. That didn’t work either.

At this point, my allotted time was up. If I wanted to have something to demo by the end of the day, I needed to switch gears. So I did.

I used Leaflet.js to create the maps I wanted using client-side JavaScript. Here’s the JavaScript code I wrote.

It waits until the page has finished loading, then it searches for any instances of the h-geo microformat (a way of encoding latitude and longitude coordinates in HTML). If there are three or more, it generates a script element to pull in the Leaflet library, and a corresponding style element. Then it draws the map with the polyline on it. I ended up using Stamen’s beautiful watercolour map tiles.

Had some fun at Indie Web Camp Brighton on the weekend messing around with @Stamen’s lovely watercolour map tiles. (I was trying to create Indiana Jones style travel maps for my site …a different kind of Indy web.)

That’s what I demoed at the end of the day.

But I wasn’t happy with it.

Sure, it looked good, but displaying the map required requests for a script, a style sheet, and multiple map tiles. I made sure that it didn’t hold up the loading of the rest of the page, but it still felt wasteful.

So after Indie Web Camp, I went back to investigate static maps again. This time I did finally manage to find some PHP code for encoding lat/lon coordinates into a polyline that worked. Finally I was able to construct URLs for a static map image that displays a line connecting multiple points with a line.

I’ve put this maps on any of the archive pages that also have calendar heat maps. Some examples:

If you go back much further than that, the maps start to trail off. That’s because I wasn’t geotagging everything from the start.

I’m pretty happy with the final results. It’s certainly far more responsible from a performance point of view. Oh, and I’ve also got the maps inside a picture element so that I can swap out the tiles if you switch to dark mode.

It’s a shame that I can’t use the lovely Stamen watercolour tiles for these static maps though.

Web talk

At the start of this month I was in Amsterdam for a series of back-to-back events: Indie Web Camp Amsterdam, View Source, and Fronteers. That last one was where Remy and I debuted talk we’d been working on.

The Fronteers folk have been quick off the mark so the video is already available. I’ve also published the text of the talk here:

How We Built The World Wide Web In Five Days

This was a fun talk to put together. The first challenge was figuring out the right format for a two-person talk. It quickly became clear that Remy’s focus would be on the events of the five days we spent at CERN, whereas my focus would be on the history of computing, hypertext, and networks leading up to the creation of the web.

Now, we could’ve just done everything chronologically, but that would mean I’d do the first half of the talk and Remy would do the second half. That didn’t appeal. And it sounded kind of boring. So then we come up with the idea of interweaving the two timelines.

That worked remarkably well. The talk starts with me describing the creation of CERN in the 1950s. Then Remy talks about the first day of the hack week. I then talk about events in the 1960s. Remy talks about the second day at CERN. This continues until we join up about half way through the talk: I’ve arrived at the moment that Tim Berners-Lee first published the proposal for the World Wide Web, and Remy has arrived at the point of having running code.

At this point, the presentation switches gears and turns into a demo. I do not have the fortitude to do a live demo, so this was all down to Remy. He did it flawlessly. I have so much respect for people brave enough to do live demos, and do them well.

But the talk doesn’t finish there. There’s a coda about our return to CERN a month after the initial hack week. This was an opportunity for both of us to close out the talk with our hopes and dreams for the World Wide Web.

I know I’m biased, but I thought the structure of the presentation worked really well: two interweaving timelines culminating in a demo and finishing with the big picture.

There was a forcing function on preparing this presentation: Remy was moving house, and I was already going to be away speaking at some other events. That limited the amount of time we could be in the same place to practice the talk. In the end, I think that might have helped us make the most of that time.

We were both feeling the pressure to tell this story well—it means so much to us. Personally, I found that presenting with Remy made me up my game. Like I said:

It’s been a real treat working with Remy on this. Don’t tell him I said this, but he’s kind of a web hero of mine, so this was a real honour and a privilege for me.

This talk could have easily turned into a boring slideshow of “what we did on our holidays”, but I think we managed to successfully avoid that trap. We’re both proud of this talk and we’d love to give it again some time. If you’d like it at your event, get in touch.

In the meantime, you can read the text, watch the video, or look at the slides (but the slides really don’t make much sense in isolation).

The Web Share API in Safari on iOS

I implemented the Web Share API over on The Session back when it was first available in Chrome in Android. It’s a nifty and quite straightforward API that allows websites to make use of the “sharing drawer” that mobile operating systems provide from within a web browser.

I already had sharing buttons that popped open links to Twitter, Facebook, and email. You can see these sharing buttons on individual pages for tunes, recordings, sessions, and so on.

I was already intercepting clicks on those buttons. I didn’t have to add too much to also check for support for the Web Share API and trigger that instead:

if (navigator.share) {
  navigator.share(
    {
      title: document.querySelector('title').textContent,
      text: document.querySelector('meta[name="description"]').getAttribute('content'),
      url: document.querySelector('link[rel="canonical"]').getAttribute('href')
    }
  );
}

That worked a treat. As you can see, there are three fields you can pass to the share() method: title, text, and url. You don’t have to provide all three.

Earlier this year, Safari on iOS shipped support for the Web Share API. I didn’t need to do anything. ‘Cause that’s how standards work. You can make use of APIs before every browser supports them, and then your website gets better and better as more and more browsers add support.

But I recently discovered something interesting about the iOS implementation.

When the share() method is triggered, iOS provides multiple ways of sharing: Messages, Airdrop, email, and so on. But the simplest option is the one labelled “copy”, which copies to the clipboard.

Here’s the thing: if you’ve provided a text parameter to the share() method then that’s what’s going to get copied to the clipboard—not the URL.

That’s a shame. Personally, I think the url field should take precedence. But I don’t think this is a bug, per se. There’s nothing in the spec to say how operating systems should handle the data sent via the Web Share API. Still, I think it’s a bit counterintuitive. If I’m looking at a web page, and I opt to share it, then surely the URL is the most important piece of data?

I’m not even sure where to direct this feedback. I guess it’s under the purview of the Safari team, but it also touches on OS-level interactions. Either way, I hope that somebody at Apple will consider changing the current behaviour for copying Web Share data to the clipboard.

In the meantime, I’ve decided to update my code to remove the text parameter:

if (navigator.share) {
  navigator.share(
    {
      title: document.querySelector('title').textContent,
      url: document.querySelector('link[rel="canonical"]').getAttribute('href')
    }
  );
}

If the behaviour of Safari on iOS changes, I’ll reinstate the missing field.

By the way, if you’re making progressive web apps that have display: standalone in the web app manifest, please consider using the Web Share API. When you remove the browser chrome, you’re removing the ability for users to easily share URLs. The Web Share API gives you a way to reinstate that functionality.

Something for the weekend

Your weekends are valuable. Spend them wisely. I have some suggestion on how you might spend next weekend, October 19th and 20th, depending on where you are in the world.

If you’re in the bay area, or anywhere near San Francisco, I highly recommend that you go to Science Hack Day—two days of science, hacking, and fun. This will be the last one in San Francisco so don’t miss your chance.

If you’re in the south of England, or anywhere near Brighton, come along to Indie Web Camp. Saturday will feature discussions on owning your data. Sunday will be a day of doing. I’ve written about previous Indie Web Camps before, and I really can’t recommend it highly enough!

Do me a favour and register for a spot—it’s free—so I’ve got some idea of numbers. Looking forward to seeing you there!

Dark mode

I had a very productive time at Indie Web Camp Amsterdam. The format really lends itself to getting the most of a weekend—one day of discussions followed by one day of hands-on making and doing. You should definitely come along to Indie Web Camp Brighton on October 19th and 20th to experience it for yourself.

By the end of the “doing” day, I had something fun to demo—a dark mode for my website.

Y’know, when I first heard about Apple adding dark mode to their OS—and also to CSS—I thought, “Oh, great, Apple are making shit up again!” But then I realised that, like user style sheets, this is one more reminder to designers and developers that they don’t get the last word—users do.

Applying the dark mode styles is pretty straightforward in theory. You put the styles inside this media query:

@media (prefers-color-scheme: dark) {
...
}

Rather than over-riding every instance of a colour in my style sheet, I decided I’d do a little bit of refactoring first and switch to using CSS custom properties (or variables, if you will).

:root {
  --background-color: #fff;
  --text-color: #333;
  --link-color: #b52;
}
body {
  background-color: var(--background-color);
  color: var(--text-color);
}
a {
  color: var(--link-color);
}

Then I can over-ride the custom properties without having to touch the already-declared styles:

@media (prefers-color-scheme: dark) {
  :root {
    --background-color: #111416
    --text-color: #ccc;
    --link-color: #f96;
  }
}

All in all, I have about a dozen custom properties for colours—variations for text, backgrounds, and interface elements like links and buttons.

By using custom properties and the prefers-color-scheme media query, I was 90% of the way there. But the devil is in the details.

I have SVGs of sparklines on my homepage. The SVG has a hard-coded colour value in the stroke attribute of the path element that draws the sparkline. Fortunately, this can be over-ridden in the style sheet:

svg.activity-sparkline path {
  stroke: var(--text-color);
}

The real challenge came with the images I use in the headers of my pages. They’re JPEGs with white corners on one side and white gradients on the other.

header images

I could make them PNGs to get transparency, but the file size would shoot up—they’re photographic images (with a little bit of scan-line treatment) so JPEGs (or WEBPs) are the better format. Then I realised I could use CSS to recreate the two effects:

  1. For the cut-out triangle in the top corner, there’s clip-path.
  2. For the gradient, there’s …gradients!
background-image: linear-gradient(
  to right,
  transparent 50%,
  var(—background-color) 100%
);

Oh, and I noticed that when I applied the clip-path for the corners, it had no effect in Safari. It turns out that after half a decade of support, it still only exists with -webkit prefix. That’s just ridiculous. At this point we should be burning vendor prefixes with fire. I can’t believe that Apple still ships standardised CSS properties that only work with a prefix.

In order to apply the CSS clip-path and gradient, I needed to save out the images again, this time without the effects baked in. I found the original Photoshop file I used to export the images. But I don’t have a copy of Photoshop any more. I haven’t had a copy of Photoshop since Adobe switched to their Mafia model of pricing. A quick bit of searching turned up Photopea, which is pretty much an entire recreation of Photoshop in the browser. I was able to open my old PSD file and re-export my images.

LEGO clone trooper Brighton bandstand Scaffolding Tokyo Florence

Let’s just take a moment here to pause and reflect on the fact that we can now use CSS to create all sorts of effects that previously required a graphic design tool like Photoshop. I could probably do those raster scan lines with CSS if I were smart enough.

dark mode

This is what I demo’d at the end of Indie Web Camp Amsterdam, and I was pleased with the results. But fate had an extra bit of good timing in store for me.

The very next day at the View Source conference, Melanie Richards gave a fantastic talk called The Tailored Web: Effectively Honoring Visual Preferences (seriously, conference organisers, you want this talk on your line-up). It was packed with great insights and advice on impementing dark mode, like this little gem for adjusting images:

@media (prefers-color-scheme: dark) {
  img {
    filter: brightness(.8) contrast(1.2);
  }
}

Melanie also pointed out that you can indicate the presence of dark mode styles to browsers, although the mechanism is yet to shake out. You can do it in CSS:

:root {
  color-scheme: light dark;
}

But you can also do it in HTML:

That allows browsers to swap out replaced content; interface elements like form fields and dropdowns.

Oh, and one other addition I added after the fact was swapping out map imagery by using the picture element to point to darker map tiles:

<picture>
<source media="(prefers-color-scheme: dark)" srcset="https://api.mapbox.com/styles/v1/mapbox/dark-v10/static...">
<img src="https://api.mapbox.com/styles/v1/mapbox/outdoors-v10/static..." alt="map">
</picture>

light map dark map

So now I’ve got a dark mode for my website. Admittedly, it’s for just one of the eight style sheets. I’ve decided that, while I’ll update my default styles at every opportunity, I’m going to preservethe other skins as they are, like the historical museum pieces they are.

If you’re on the latest version of iOS, go ahead and toggle the light and dark options in your system preferences to flip between this site’s colour schemes.

Travel talk

It’s been a busy two weeks of travelling and speaking. Last week I spoke at Finch Conf in Edinburgh, Code Motion in Madrid, and Generate CSS in London. This week I was at Indie Web Camp, View Source, and Fronteers, all in Amsterdam.

The Edinburgh-Madrid-London whirlwind wasn’t ideal. I gave the opening talk at Finch Conf, then immediately jumped in a taxi to get to the airport to fly to Madrid, so I missed all the excellent talks. I had FOMO for a conference I actually spoke at.

I did get to spend some time at Code Motion in Madrid, but that was a waste of time. It was one of those multi-track events where the trade show floor is prioritised over the talks (and the speakers don’t get paid). I gave my talk to a mostly empty room—the classic multi-track experience. On the plus side, I had a wonderful time with Jessica exploring Madrid’s many tapas delights. The food and drink made up for the sub-par conference.

I flew back from Madrid to the UK, and immediately went straight to London to deliver the closing talk of Generate CSS. So once again, I didn’t get to see any of the other talks. That’s a real shame—it sounds like they were all excellent.

The day after Generate though, I took the Eurostar to Amsterdam. That’s where I’ve been ever since. There were just as many events as in the previous week, but because they were all in Amsterdam, I could savour them properly, instead of spending half my time travelling.

Indie Web Camp Amsterdam was excellent, although I missed out on the afternoon discussions on the first day because I popped over to the Mozilla Tech Speakers event happening at the same time. I was there to offer feedback on lightning talks. I really, really enjoyed it.

I’d really like to do more of this kind of thing. There aren’t many activities I feel qualified to give advice on, but public speaking is an exception. I’ve got plenty of experience that I’m eager to share with up-and-coming speakers. Also, I got to see some really great lightning talks!

Then it was time for View Source. There was a mix of talks, panels, and breakout conversation corners. I saw some fantastic talks by people I hadn’t seen speak before: Melanie Richards, Ali Spittal, Sharell Bryant, and Tejas Kumar. I gave the closing keynote, which was warmly received—that’s always very gratifying.

After one day of rest, it was time for Fronteers. This was where myself and Remy gave the joint talk we’ve been working on:

Neither of us is under any illusions about the nature of a joint talk. It’s not half as much work; it’s more like twice the work. We’ve both seen enough uneven joint presentations to know what we want to avoid.

I’m happy to say that it went off without a hitch. Remy definitely had the tougher task—he did a live demo. Needless to say, he did it flawlessly. It’s been a real treat working with Remy on this. Don’t tell him I said this, but he’s kind of a web hero of mine, so this was a real honour and a privilege for me.

I’ve got some more speaking engagements ahead of me. Most of them are in Europe so I’m going to do my utmost to travel to them by train. Flying is usually more convenient but it’s terrible for my carbon footprint. I’m feeling pretty guilty about that Madrid trip; I need to make ammends.

I’ll be travelling to France next week for Paris Web. Taking the Eurostar is a no-brainer for that one. Straight after that Jessica and I will be going to Frankfurt for the book fair. Taking the train from Paris to Frankfurt will be nice and straightforward.

I’ll be back in Brighton for Indie Web Camp on the weekend of October 19th and 20th—you should come!—and then I’ll be heading off to Antwerp for Full Stack Fest. Anywhere in Belgium is easily reachable by train so that’ll be another Eurostar journey.

After that, it gets a little trickier. I’ll be going to Berlin for Beyond Tellerrand but I’m not sure I can make it work by train. Same goes for Web Clerks in Vienna. Cities that far east are tough to get to by train in a reasonable amount of time (although I realise that, compared to many others, I have the luxury of spending time travelling by train).

Then there are the places that I can only get to by plane. There’s the United States. I’ll be speaking at An Event Apart in San Francisco in December. A flight is unavoidable. Last time we went to the States, Jessica and I travelled by ocean liner. But that isn’t any better for the environment, given the low-grade fuel burned by ships.

And then there’s Ireland. I make trips back there to see my mother, but there’s no alternative to flying or taking a ferry—neither are ideal for the environment. At least I can offset the carbon from my flights; the travel equivalent to putting coins in the swear jar.

Don’t get me wrong—I’m not moaning about the amount of travel involved in going to conferences and workshops. It’s fantastic that I get to go to new and interesting places. That’s something I hope I never take for granted. But I can’t ignore the environmental damage I’m doing. I’ll be making more of an effort to travel by train to Europe’s many excellent web events. While I’m at it, I can ask Paul for his trainspotter expertise.

Going offline with microformats

For the offline page on my website, I’ve been using a mixture of the Cache API and the localStorage API. My service worker script uses the Cache API to store copies of pages for offline retrieval. But I used the localStorage API to store metadata about the page—title, description, and so on. Then, my offline page would rifle through the pages stored in a cache, and retreive the corresponding metadata from localStorage.

It all worked fine, but as soon as I read Remy’s post about the forehead-slappingly brilliant technique he’s using, I knew I’d be switching my code over. Instead of using localStorage—or any other browser API—to store and retrieve metadata, he uses the pages themselves! Using the Cache API, you can examine the contents of the pages you’ve stored, and get at whatever information you need:

I realised I didn’t need to store anything. HTML is the API.

Refactoring the code for my offline page felt good for a couple of reasons. First of all, I was able to remove a dependency—localStorage—and simplify the JavaScript. That always feels good. But the other reason for the warm fuzzies is that I was able to use data instead of metadata.

Many years ago, Cory Doctorow wrote a piece called Metacrap. In it, he enumerates the many issues with metadata—data about data. The source of many problems is when the metadata is stored separately from the data it describes. The data may get updated, without a corresponding update happening to the metadata. Metadata tends to rot because it’s invisible—out of sight and out of mind.

In fact, that’s always been at the heart of one of the core principles behind microformats. Instead of duplicating information—once as data and again as metadata—repurpose the visible data; mark it up so its meta-information is directly attached to the information itself.

So if you have a person’s contact details on a web page, rather than repeating that information somewhere else—in the head of the document, say—you could instead attach some kind of marker to indicate which bits of the visible information are contact details. In the case of microformats, that’s done with class attributes. You can mark up a page that already has your contact information with classes from the h-card microformat.

Here on my website, I’ve marked up my blog posts, articles, and links using the h-entry microformat. These classes explicitly mark up the content to say “this is the title”, “this is the content”, and so on. This makes it easier for other people to repurpose my content. If, for example, I reply to a post on someone else’s website, and ping them with a webmention, they can retrieve my post and know which bit is the title, which bit is the content, and so on.

When I read Remy’s post about using the Cache API to retrieve information directly from cached pages, I knew I wouldn’t have to do much work. Because all of my posts are already marked up with h-entry classes, I could use those hooks to create a nice offline page.

The markup for my offline page looks like this:

<h1>Offline</h1>
<p>Sorry. It looks like the network connection isn’t working right now.</p>
<div id="history">
</div>

I’ll populate that “history” div with information from a cache called “pages” that I’ve created using the Cache API in my service worker.

I’m going to use async/await to do this because there are lots of steps that rely on the completion of the step before. “Open this cache, then get the keys of that cache, then loop through the pages, then…” All of those thens would lead to some serious indentation without async/await.

All async functions have to have a name—no anonymous async functions allowed. I’m calling this one listPages, just like Remy is doing. I’m making the listPages function execute immediately:

(async function listPages() {
...
})();

Now for the code to go inside that immediately-invoked function.

I create an array called browsingHistory that I’ll populate with the data I’ll use for that “history” div.

const browsingHistory = [];

I’m going to be parsing web pages later on, so I’m going to need a DOM parser. I give it the imaginative name of …parser.

const parser = new DOMParser();

Time to open up my “pages” cache. This is the first await statement. When the cache is opened, this promise will resolve and I’ll have access to this cache using the variable …cache (again with the imaginative naming).

const cache = await caches.open('pages');

Now I get the keys of the cache—that’s a list of all the page requests in there. This is the second await. Once the keys have been retrieved, I’ll have a variable that’s got a list of all those pages. You’ll never guess what I’m calling the variable that stores the keys of the cache. That’s right …keys!

const keys = await cache.keys();

Time to get looping. I’m getting each request in the list of keys using a for/of loop:

for (const request of keys) {
...
}

Inside the loop, I pull the page out of the cache using the match() method of the Cache API. I’ll store what I get back in a variable called response. As with everything involving the Cache API, this is asynchronous so I need to use the await keyword here.

const response = await cache.match(request);

I’m not interested in the headers of the response. I’m specifically looking for the HTML itself. I can get at that using the text() method. Again, it’s asynchronous and I want this promise to resolve before doing anything else, so I use the await keyword. When the promise resolves, I’ll have a variable called html that contains the body of the response.

const html = await response.text();

Now I can use that DOM parser I created earlier. I’ve got a string of text in the html variable. I can generate a Document Object Model from that string using the parseFromString() method. This isn’t asynchronous so there’s no need for the await keyword.

const dom = parser.parseFromString(html, 'text/html');

Now I’ve got a DOM, which I have creatively stored in a variable called …dom.

I can poke at it using DOM methods like querySelector. I can test to see if this particular page has an h-entry on it by looking for an element with a class attribute containing the value “h-entry”:

if (dom.querySelector('.h-entry h1.p-name') {
...
}

In this particular case, I’m also checking to see if the h1 element of the page is the title of the h-entry. That’s so that index pages (like my home page) won’t get past this if statement.

Inside the if statement, I’m going to store the data I retrieve from the DOM. I’ll save the data into an object called …data!

const data = new Object;

Well, the first piece of data isn’t actually in the markup: it’s the URL of the page. I can get that from the request variable in my for loop.

data.url = request.url;

I’m going to store the timestamp for this h-entry. I can get that from the datetime attribute of the time element marked up with a class of dt-published.

data.timestamp = new Date(dom.querySelector('.h-entry .dt-published').getAttribute('datetime'));

While I’m at it, I’m going to grab the human-readable date from the innerText property of that same time.dt-published element.

data.published = dom.querySelector('.h-entry .dt-published').innerText;

The title of the h-entry is in the innerText of the element with a class of p-name.

data.title = dom.querySelector('.h-entry .p-name').innerText;

At this point, I am actually going to use some metacrap instead of the visible h-entry content. I don’t output a description of the post anywhere in the body of the page, but I do put it in the head in a meta element. I’ll grab that now.

data.description = dom.querySelector('meta[name="description"]').getAttribute('content');

Alright. I’ve got a URL, a timestamp, a publication date, a title, and a description, all retrieved from the HTML. I’ll stick all of that data into my browsingHistory array.

browsingHistory.push(data);

My if statement and my for/in loop are finished at this point. Here’s how the whole loop looks:

for (const request of keys) {
  const response = await cache.match(request);
  const html = await response.text();
  const dom = parser.parseFromString(html, 'text/html');
  if (dom.querySelector('.h-entry h1.p-name')) {
    const data = new Object;
    data.url = request.url;
    data.timestamp = new Date(dom.querySelector('.h-entry .dt-published').getAttribute('datetime'));
    data.published = dom.querySelector('.h-entry .dt-published').innerText;
    data.title = dom.querySelector('.h-entry .p-name').innerText;
    data.description = dom.querySelector('meta[name="description"]').getAttribute('content');
    browsingHistory.push(data);
  }
}

That’s the data collection part of the code. Now I’m going to take all that yummy information an output it onto the page.

First of all, I want to make sure that the browsingHistory array isn’t empty. There’s no point going any further if it is.

if (browsingHistory.length) {
...
}

Within this if statement, I can do what I want with the data I’ve put into the browsingHistory array.

I’m going to arrange the data by date published. I’m not sure if this is the right thing to do. Maybe it makes more sense to show the pages in the order in which you last visited them. I may end up removing this at some point, but for now, here’s how I sort the browsingHistory array according to the timestamp property of each item within it:

browsingHistory.sort( (a,b) => {
  return b.timestamp - a.timestamp;
});

Now I’m going to concatenate some strings. This is the string of HTML text that will eventually be put into the “history” div. I’m storing the markup in a string called …markup (my imagination knows no bounds).

let markup = '<p>But you still have something to read:</p>';

I’m going to add a chunk of markup for each item of data.

browsingHistory.forEach( data => {
  markup += `
<h2><a href="${ data.url }">${ data.title }</a></h2>
<p>${ data.description }</p>
<p class="meta">${ data.published }</p>
`;
});

With my markup assembled, I can now insert it into the “history” part of my offline page. I’m using the handy insertAdjacentHTML() method to do this.

document.getElementById('history').insertAdjacentHTML('beforeend', markup);

Here’s what my finished JavaScript looks like:

<script>
(async function listPages() {
  const browsingHistory = [];
  const parser = new DOMParser();
  const cache = await caches.open('pages');
  const keys = await cache.keys();
  for (const request of keys) {
    const response = await cache.match(request);
    const html = await response.text();
    const dom = parser.parseFromString(html, 'text/html');
    if (dom.querySelector('.h-entry h1.p-name')) {
      const data = new Object;
      data.url = request.url;
      data.timestamp = new Date(dom.querySelector('.h-entry .dt-published').getAttribute('datetime'));
      data.published = dom.querySelector('.h-entry .dt-published').innerText;
      data.title = dom.querySelector('.h-entry .p-name').innerText;
      data.description = dom.querySelector('meta[name="description"]').getAttribute('content');
      browsingHistory.push(data);
    }
  }
  if (browsingHistory.length) {
    browsingHistory.sort( (a,b) => {
      return b.timestamp - a.timestamp;
    });
    let markup = '<p>But you still have something to read:</p>';
    browsingHistory.forEach( data => {
      markup += `
<h2><a href="${ data.url }">${ data.title }</a></h2>
<p>${ data.description }</p>
<p class="meta">${ data.published }</p>
`;
    });
    document.getElementById('history').insertAdjacentHTML('beforeend', markup);
  }
})();
</script>

I’m pretty happy with that. It’s not too long but it’s still quite readable (I hope). It shows that the Cache API and the h-entry microformat are a match made in heaven.

If you’ve got an offline strategy for your website, and you’re using h-entry to mark up your content, feel free to use that code.

If you don’t have an offline strategy for your website, there’s a book for that.