Tags: work

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Thursday, December 6th, 2018

Big ol’ Ball o’ JavaScript | Brad Frost

Backend logic? JavaScript. Styles? We do that in JavaScript now. Markup? JavaScript. Anything else? JavaScript.

Historically, different languages suggested different roles. “This language does style.” “This language does structure.” But now it’s “This JavaScript does style.” “This JavaScript does structure.” “This JavaScript does database queries.”

Introducing Background Fetch  |  Web  |  Google Developers

I’m going to have to read through this article by Jake a few times before I begin to wrap my head around this background fetch thing, but it looks like it would be perfect for something like the dConstruct Audio Archive, where fairly large files can be saved for offline listening.

Mistletoe Offline

This article first appeared in 24 Ways, the online advent calendar for geeks.

It’s that time of year, when we gather together as families to celebrate the life of the greatest person in history. This man walked the Earth long before us, but he left behind words of wisdom. Those words can guide us every single day, but they are at the forefront of our minds during this special season.

I am, of course, talking about Murphy, and the golden rule he gave unto us:

Anything that can go wrong will go wrong.

So true! I mean, that’s why we make sure we’ve got nice 404 pages. It’s not that we want people to ever get served a File Not Found message, but we acknowledge that, despite our best efforts, it’s bound to happen sometime. Murphy’s Law, innit?

But there are some Murphyesque situations where even your lovingly crafted 404 page won’t help. What if your web server is down? What if someone is trying to reach your site but they lose their internet connection? These are all things than can—and will—go wrong.

I guess there’s nothing we can do about those particular situations, right?

Wrong!

A service worker is a Murphy-battling technology that you can inject into a visitor’s device from your website. Once it’s installed, it can intercept any requests made to your domain. If anything goes wrong with a request—as is inevitable—you can provide instructions for the browser. That’s your opportunity to turn those server outage frowns upside down. Take those network connection lemons and make network connection lemonade.

If you’ve got a custom 404 page, why not make a custom offline page too?

Get your server in order

Step one is to make …actually, wait. There’s a step before that. Step zero. Get your site running on HTTPS, if it isn’t already. You won’t be able to use a service worker unless everything’s being served over HTTPS, which makes sense when you consider the awesome power that a service worker wields.

If you’re developing locally, service workers will work fine for localhost, even without HTTPS. But for a live site, HTTPS is a must.

Make an offline page

Alright, assuming your site is being served over HTTPS, then step one is to create an offline page. Make it as serious or as quirky as is appropriate for your particular brand. If the website is for a restaurant, maybe you could put the telephone number and address of the restaurant on the custom offline page (unsolicited advice: you could also put this on the home page, you know). Here’s an example of the custom offline page for this year’s Ampersand conference.

When you’re done, publish the offline page at suitably imaginative URL, like, say /offline.html.

Pre-cache your offline page

Now create a JavaScript file called serviceworker.js. This is the script that the browser will look to when certain events are triggered. The first event to handle is what to do when the service worker is installed on the user’s device. When that happens, an event called install is fired. You can listen out for this event using addEventListener:

addEventListener('install', installEvent => {
// put your instructions here.
}); // end addEventListener

In this case, you want to make sure that your lovingly crafted custom offline page is put into a nice safe cache. You can use the Cache API to do this. You get to create as many caches as you like, and you can call them whatever you want. Here, I’m going to call the cache Johnny just so I can refer to it as JohnnyCache in the code:

addEventListener('install', installEvent => {
  installEvent.waitUntil(
    caches.open('Johnny')
    .then( JohnnyCache => {
      JohnnyCache.addAll([
       '/offline.html'
      ]); // end addAll
     }) // end open.then
  ); // end waitUntil
}); // end addEventListener

I’m betting that your lovely offline page is linking to a CSS file, maybe an image or two, and perhaps some JavaScript. You can cache all of those at this point:

addEventListener('install', installEvent => {
  installEvent.waitUntil(
    caches.open('Johnny')
    .then( JohnnyCache => {
      JohnnyCache.addAll([
       '/offline.html',
       '/path/to/stylesheet.css',
       '/path/to/javascript.js',
         '/path/to/image.jpg'
      ]); // end addAll
     }) // end open.then
  ); // end waitUntil
}); // end addEventListener

Make sure that the URLs are correct. If just one of the URLs in the list fails to resolve, none of the items in the list will be cached.

Intercept requests

The next event you want to listen for is the fetch event. This is probably the most powerful—and, let’s be honest, the creepiest—feature of a service worker. Once it has been installed, the service worker lurks on the user’s device, waiting for any requests made to your site. Every time the user requests a web page from your site, a fetch event will fire. Every time that page requests a style sheet or an image, a fetch event will fire. You can provide instructions for what should happen each time:

addEventListener('fetch', fetchEvent => {
// What happens next is up to you!
}); // end addEventListener

Let’s write a fairly conservative script with the following logic:

  • Whenever a file is requested,
  • First, try to fetch it from the network,
  • But if that doesn’t work, try to find it in the cache,
  • But if that doesn’t work, and it’s a request for a web page, show the custom offline page instead.

Here’s how that translates into JavaScript:

// Whenever a file is requested
addEventListener('fetch', fetchEvent => {
  const request = fetchEvent.request;
  fetchEvent.respondWith(
    // First, try to fetch it from the network
    fetch(request)
    .then( responseFromFetch => {
      return responseFromFetch;
    }) // end fetch.then
    // But if that doesn't work
    .catch( fetchError => {
      // try to find it in the cache
      caches.match(request)
      .then( responseFromCache => {
        if (responseFromCache) {
         return responseFromCache;
       // But if that doesn't work
       } else {
         // and it's a request for a web page
         if (request.headers.get('Accept').includes('text/html')) {
           // show the custom offline page instead
           return caches.match('/offline.html');
         } // end if
       } // end if/else
     }) // end match.then
   }) // end fetch.catch
  ); // end respondWith
}); // end addEventListener

I am fully aware that I may have done some owl-drawing there. If you need a more detailed breakdown of what’s happening at each point in the code, I’ve written a whole book for you. It’s the perfect present for Murphymas.

Hook up your service worker script

You can publish your service worker script at /serviceworker.js but you still need to tell the browser where to look for it. You can do that using JavaScript. Put this in an existing JavaScript file that you’re calling in to every page on your site, or add this in a script element at the end of every page’s HTML:

if (navigator.serviceWorker) {
  navigator.serviceWorker.register('/serviceworker.js');
}

That tells the browser to start installing the service worker, but not without first checking that the browser understands what a service worker is. When it comes to JavaScript, feature detection is your friend.

You might already have some JavaScript files in a folder like /assets/js/ and you might be tempted to put your service worker script in there too. Don’t do that. If you do, the service worker will only be able to handle requests made to for files within /assets/js/. By putting the service worker script in the root directory, you’re making sure that every request can be intercepted.

Go further!

Nicely done! You’ve made sure that if—no, when—a visitor can’t reach your website, they’ll get your hand-tailored offline page. You have temporarily defeated the forces of chaos! You have briefly fought the tide of entropy! You have made a small but ultimately futile gesture against the inevitable heat-death of the universe!

This is just the beginning. You can do more with service workers.

What if, every time you fetched a page from the network, you stored a copy of that page in a cache? Then if that person tries to reach that page later, but they’re offline, you could show them the cached version.

Or, what if instead of reaching out the network first, you checked to see if a file is in the cache first? You could serve up that cached version—which would be blazingly fast—and still fetch a fresh version from the network in the background to pop in the cache for next time. That might be a good strategy for images.

So many options! The hard part isn’t writing the code, it’s figuring out the steps you want to take. Once you’ve got those steps written out, then it’s a matter of translating them into JavaScript.

Inevitably there will be some obstacles along the way—usually it’s a misplaced curly brace or a missing parenthesis. Don’t be too hard on yourself if your code doesn’t work at first. That’s just Murphy’s Law in action.

Wednesday, December 5th, 2018

Going Offline First (Video Series)

A five-part video series from Ire on how she built the “save for offline” functionality on her site.

The first one is about getting a set set up on Ghost so you can probably safely skip that one and go straight to the second video to get down to the nitty-gritty of the Cache API and service workers.

Tuesday, December 4th, 2018

Mistletoe Offline ◆ 24 ways

They let me write a 24 Ways article again. Will they never learn?

This one’s a whirlwind tour of using a service worker to provide a custom offline page, in the style of Going Offline.

By the way, just for the record, I initially rejected this article’s title out of concern that injecting a Cliff Richard song into people’s brains was cruel and unusual punishment. I was overruled.

Monday, December 3rd, 2018

Reluctant Gatekeeping: The Problem With Full Stack | HeydonWorks

The value you want form a CSS expert is their CSS, not their JavaScript, so it’s absurd to make JavaScript a requirement.

Absolutely spot on! And it cuts both ways:

Put CSS in JS and anyone who wishes to write CSS now has to know JavaScript. Not just JavaScript, but —most likely—the specific ‘flavor’ of JavaScript called React. That’s gatekeeping, first of all, but the worst part is the JavaScript aficionado didn’t want CSS on their plate in the first place.

Tuesday, November 27th, 2018

Front-end development is not a problem to be solved | CSS-Tricks

The sentiment is that front-end development is a problem to be solved: “if we just have the right tools and frameworks, then we might never have to write another line of HTML or CSS ever again!” And oh boy what a dream that would be, right?

Well, no, actually. I certainly don’t think that front-end development is a problem at all.

What Robin said.

I reckon HTML and CSS deserve better than to be processed, compiled, and spat out into the browser, whether that’s through some build process, app export, or gigantic framework library of stuff that we half understand. HTML and CSS are two languages that deserve our care and attention to detail. Writing them is a skill.

Saturday, November 24th, 2018

PushAPI without Notifications | Seblog

Remember when I wrote about using push without notifications? Sebastiaan has written up the details of the experiment he conducted at Indie Web Camp Berlin.

Tuesday, November 20th, 2018

Web workers vs Service workers vs Worklets

A great primer by Ire:

Web workers, service workers, and worklets are all scripts that run on a separate thread. So what are the differences between these three types of workers?

Push and ye shall receive | CSS-Tricks

Imagine a PWA podcast app that works offline and silently receives and caches new podcasts. Sweet. Now we need a permissions model that allows for silent notifications.

Tuesday, November 13th, 2018

Inlining or Caching? Both Please! | Filament Group, Inc., Boston, MA

This just blew my mind! A fiendishly clever pattern that allows you to inline resources (like critical CSS) and cache that same content for later retrieval by a service worker.

Crazy clever!

Sunday, November 11th, 2018

Push without notifications

On the first day of Indie Web Camp Berlin, I led a session on going offline with service workers. This covered all the usual use-cases: pre-caching; custom offline pages; saving pages for offline reading.

But on the second day, Sebastiaan spent a fair bit of time investigating a more complex use of service workers with the Push API.

The Push API is what makes push notifications possible on the web. There are a lot of moving parts—browser, server, service worker—and, frankly, it’s way over my head. But I’m familiar with the general gist of how it works. Here’s a typical flow:

  1. A website prompts the user for permission to send push notifications.
  2. The user grants permission.
  3. A whole lot of complicated stuff happens behinds the scenes.
  4. Next time the website publishes something relevant, it fires a push message containing the details of the new URL.
  5. The user’s service worker receives the push message (even if the site isn’t open).
  6. The service worker creates a notification linking to the URL, interrupting the user, and generally adding to the weight of information overload.

Here’s what Sebastiaan wanted to investigate: what if that last step weren’t so intrusive? Here’s the alternate flow he wanted to test:

  1. A website prompts the user for permission to send push notifications.
  2. The user grants permission.
  3. A whole lot of complicated stuff happens behinds the scenes.
  4. Next time the website publishes something relevant, it fires a push message containing the details of the new URL.
  5. The user’s service worker receives the push message (even if the site isn’t open).
  6. The service worker fetches the contents of the URL provided in the push message and caches the page. Silently.

It worked.

I think this could be a real game-changer. I don’t know about you, but I’m very, very wary of granting websites the ability to send me push notifications. In fact, I don’t think I’ve ever given a website permission to interrupt me with push notifications.

You’ve seen the annoying permission dialogues, right?

In Firefox, it looks like this:

Will you allow name-of-website to send notifications?

[Not Now] [Allow Notifications]

In Chrome, it’s:

name-of-website wants to

Show notifications

[Block] [Allow]

But in actual fact, these dialogues are asking for permission to do two things:

  1. Receive messages pushed from the server.
  2. Display notifications based on those messages.

There’s no way to ask for permission just to do the first part. That’s a shame. 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.

Think of the use cases:

  • I grant push permission to a magazine. When the magazine publishes a new article, it’s cached on my device.
  • I grant push permission to a podcast. Whenever a new episode is published, it’s cached on my device.
  • I grant push permission to a blog. When there’s a new blog post, it’s cached on my device.

Then when I’m on a plane, or in the subway, or in any other situation without a network connection, I could still visit these websites and get content that’s fresh to me. It’s kind of like background sync in reverse.

There’s plenty of opportunity for abuse—the cache could get filled with content. But websites can already do that, and they don’t need to be granted any permissions to do so; just by visiting a website, it can add multiple files to a cache.

So it seems that the reason for the permissions dialogue is all about displaying notifications …not so much about receiving push messages from the server.

I wish there were a way to implement this background-caching pattern without requiring the user to grant permission to a dialogue that contains the word “notification.”

I wonder if the act of adding a site to the home screen could implicitly grant permission to allow use of the Push API without notifications?

In the meantime, the proposal for periodic synchronisation (using background sync) could achieve similar results, but in a less elegant way; periodically polling for new content instead of receiving a push message when new content is published. Also, it requires permission. But at least in this case, the permission dialogue should be more specific, and wouldn’t include the word “notification” anywhere.

Saturday, November 10th, 2018

CSS Frameworks Or CSS Grid: What Should I Use For My Project? — Smashing Magazine

Rachel does some research to find out why people use CSS frameworks like Bootstrap—it can’t just be about grids, right?

It turns out there are plenty of reasons that people give for using frameworks—whether it’s CSS or JavaScript—but Rachel shares some of my misgivings on this:

In our race to get our site built quickly, our desire to make things as good as possible for ourselves as the designers and developers of the site, do we forget who we are doing this for? Do the decisions made by the framework developer match up with the needs of the users of the site you are building?

Not for the first time, I’m reminded of Rachel’s excellent post from a few years ago: Stop solving problems you don’t yet have.

CSS and Network Performance – CSS Wizardry

Harry takes a look at the performance implications of loading CSS. To be clear, this is not about the performance of CSS selectors or ordering (which really doesn’t make any difference at this point), but rather it’s about the different ways of getting rid of as much render-blocking CSS as possible.

…a good rule of thumb to remember is that your page will only render as quickly as your slowest stylesheet.

Sunday, November 4th, 2018

When your design system fails — HeyDesigner

You could create components that strike the perfect balance between reuse and context sensitivity. But defining the components of your design system is just the first step. It has to make its way into the product. If it doesn’t, a design system is like a language with no extant literature or seminal texts.

Marissa Christy outlines the reasons why your design system might struggle:

  1. The redesign isn’t prioritized
  2. The tech stack is changing
  3. Maintenance takes discipline

But she also offers advice for counteracting these forces:

  1. Get buy-in from the whole team
  2. Prioritize a lightweight re-skin on older parts of the product
  3. Treat a design system like any other product project: start small
  4. Don’t wait for others. Lead by example.
  5. Finally, don’t compare yourself to others on the internet

Monday, October 29th, 2018

Programming Sucks

There’s a theory that you can cure this by following standards, except there are more “standards” than there are things computers can actually do, and these standards are all variously improved and maligned by the personal preferences of the people coding them, so no collection of code has ever made it into the real world without doing a few dozen identical things a few dozen not even remotely similar ways. The first few weeks of any job are just figuring out how a program works even if you’re familiar with every single language, framework, and standard that’s involved, because standards are unicorns.

Sunday, October 28th, 2018

Phil Nash and Jeremy Keith Save the Safari Video Playback Day

I love this example of paying it forward:

Friday, October 26th, 2018

Silicon Valley by the Sea: Is Brighton Really a UK Startup Hub?

Terrible title; nice article. Rich speaks his brains about Clearleft and what we like about being in Brighton.

Service workers and videos in Safari

Alright, so I’ve already talked about some gotchas when debugging service worker issues. But what if you don’t even realise the problem has anything to do with your service worker?

This is not a hypothetical situation. I encountered this very thing myself. Gather ‘round the campfire, children…

One of the latest case studies on the Clearleft site is a nice write-up by Luke of designing a mobile app for Virgin Holidays. The case study includes a lovely video that demonstrates the log-in flow. I implemented that using a video element (with a poster image). Nice and straightforward. Super easy. All good.

But I hadn’t done my due diligence in browser testing (I guess I didn’t even think of it in this case). Hana informed me that the video wasn’t working at all in Safari. The poster image appeared just fine, but when you clicked on it, the video didn’t load.

I ducked, ducked, and went, uncovering what appeared to be the root of the problem. It seems that Safari is fussy about having servers support something called “byte-range requests”.

I had put the video in question on an Amazon S3 server. I came to the conclusion that S3 mustn’t support these kinds of headers correctly, or something.

Now I had a diagnosis. The next step was figuring out a solution. I thought I might have to move the video off of S3 and onto a server that I could configure a bit more.

Luckily, I never got ‘round to even starting that process. That’s good. Because it turns out that my diagnosis was completely wrong.

I came across a recent post by Phil Nash called Service workers: beware Safari’s range request. The title immediately grabbed my attention. Safari: yes! Video: yes! But service workers …wait a minute!

There’s a section in Phil’s post entitled “Diagnosing the problem”, in which he says:

I first thought it could have something to do with the CDN I’m using. There were some false positives regarding streaming video through a CDN that resulted in some extra research that was ultimately fruitless.

That described my situation exactly. Except Phil went further and nailed down the real cause of the problem:

Nginx was serving correct responses to Range requests. So was the CDN. The only other problem? The service worker. And this broke the video in Safari.

Doh! I hadn’t even thought about service workers!

Phil came up with a solution, and he has kindly shared his code.

I decided to go for a dumber solution:

if ( request.url.match(/\.(mp4)$/) ) {
  return;
}

That tells the service worker to just step out of the way when it comes to video requests. Now the video plays just fine in Safari. It’s a bit of a shame, because I’m kind of penalising all browsers for Safari’s bug, but the Clearleft site isn’t using much video at all, and in any case, it might be good not to fill up the cache with large video files.

But what’s more important than any particular solution is correctly identifying the problem. I’m quite sure I never would’ve been able to fix this issue if Phil hadn’t gone to the trouble of sharing his experience. I’m very, very grateful that he did.

That’s the bigger lesson here: if you solve a problem—even if you think it’s hardly worth mentioning—please, please share your solution. It could make all the difference for someone out there.

Service workers and browser extensions

I quite enjoy a good bug hunt. Just yesterday, myself and Cassie were doing some bugfixing together. As always, the first step was to try to reproduce the problem and then isolate it. Which reminds me…

There’ve been a few occasions when I’ve been trying to debug service worker issues. The problem is rarely in reproducing the issue—it’s isolating the cause that can be frustrating. I try changing a bit of code here, and a bit of code there, in an attempt to zero in on the problem, butwith no luck. Before long, I’m tearing my hair out staring at code that appears to have nothing wrong with it.

And that’s when I remember: browser extensions.

I’m currently using Firefox as my browser, and I have extensions installed to stop tracking and surveillance (these technologies are usually referred to as “ad blockers”, but that’s a bit of a misnomer—the issue isn’t with the ads; it’s with the invasive tracking).

If you think about how a service worker does its magic, it’s as if it’s sitting in the browser, waiting to intercept any requests to a particular domain. It’s like the service worker is the first port of call for any requests the browser makes. But then you add a browser extension. The browser extension is also waiting to intercept certain network requests. Now the extension is the first port of call, and the service worker is relegated to be next in line.

This, apparently, can cause issues (presumably depending on how the browser extension has been coded). In some situations, network requests that should work just fine start to fail, executing the catch clauses of fetch statements in your service worker.

So if you’ve been trying to debug a service worker issue, and you can’t seem to figure out what the problem might be, it’s not necessarily an issue with your code, or even an issue with the browser.

From now on when I’m troubleshooting service worker quirks, I’m going to introduce a step zero, before I even start reproducing or isolating the bug. I’m going to ask myself, “Are there any browser extensions installed?”

I realise that sounds as basic as asking “Are you sure the computer is switched on?” but there’s nothing wrong with having a checklist of basic questions to ask before moving on to the more complicated task of debugging.

I’m going to make a checklist. Then I’m going to use it …every time.