Tags: fr

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Wednesday, August 21st, 2019

Accessibility and web performance are not features, they’re the baseline | CSS-Tricks

Performance and accessibility aren’t features that can linger at the bottom of a Jira board to be considered later when it’s convenient.

Instead we must start to see inaccessible and slow websites for what they are: a form of cruelty. And if we want to build a web that is truly a World Wide Web, a place for all and everyone, a web that is accessible and fast for as many people as possible, and one that will outlive us all, then first we must make our websites something else altogether; we must make them kind.

Saturday, August 10th, 2019

Server Timing

Harry wrote a really good article all about the performance measurement Time To First Byte. Time To First Byte: What It Is and Why It Matters:

While a good TTFB doesn’t necessarily mean you will have a fast website, a bad TTFB almost certainly guarantees a slow one.

Time To First Byte has been the chink in my armour over at thesession.org, especially on the home page. Every time I ran Lighthouse, or some other performance testing tool, I’d get a high score …with some points deducted for taking too long to get that first byte from the server.

Harry’s proposed solution is to set up some Server Timing headers:

With a little bit of extra work spent implementing the Server Timing API, we can begin to measure and surface intricate timings to the front-end, allowing web developers to identify and debug potential bottlenecks previously obscured from view.

I rememberd that Drew wrote an excellent article on Smashing Magazine last year called Measuring Performance With Server Timing:

The job of Server Timing is not to help you actually time activity on your server. You’ll need to do the timing yourself using whatever toolset your backend platform makes available to you. Rather, the purpose of Server Timing is to specify how those measurements can be communicated to the browser.

He even provides some PHP code, which I was able to take wholesale and drop into the codebase for thesession.org. Then I was able to put start/stop points in my code for measuring how long some operations were taking. Then I could output the results of these measurements into Server Timing headers that I could inspect in the “Network” tab of a browser’s dev tools (Chrome is particularly good for displaying Server Timing, so I used that while I was conducting this experiment).

I started with overall database requests. Sure enough, that was where most of the time in time-to-first-byte was being spent.

Then I got more granular. I put start/stop points around specific database calls. By doing this, I was able to zero in on which operations were particularly costly. Once I had done that, I had to figure out how to make the database calls go faster.

Spoiler: I did it by adding an extra index on one particular table. It’s almost always indexes, in my experience, that make the biggest difference to database performance.

I don’t know why it took me so long to get around to messing with Server Timing headers. It has paid off in spades. I wish I had done it sooner.

And now thesession.org is positively zipping along!

Amphora. — Ethan Marcotte

There’s no sugar-coating it—AMP components are dreadfully inaccessible:

We’ve reached a point where AMP may “solve” the web’s performance issues by supercharging the web’s accessibility problem, excluding even more people from accessing the content they deserve.

Friday, August 9th, 2019

Meaning without markup: Accessibility Object Model

Hidde gives an in-depth explanation of the Accessibility Object Model, coming soon to browsers near you:

In a way, that’s a bit like what Service Workers do for the network and Houdini for style: give developers control over something that was previously done only by the browser.

Building an extensible app or library with vanilla JS | Go Make Things

This looks like a sensible approach to creating a modular architecture for a complex client-side JavaScript codebase.

I know a lot of people swear by ES6 imports, but this systems worked really well for us. It gave us a simple, modular, extensible framework we can easily build on in the future.

The 2019 Design Systems Survey by Sparkbox

The good folks at Sparkbox ran a survey on design systems. Here are the results, presented in a flagrantly anti-Tufte manner.

Redux: Lazy loading youtube embeds

Remy has an excellent improvement on that article I linked to yesterday on using srcdoc with iframes. Rather than using srcdoc instead of src, you can use srcdoc as well as src. That way you can support older browsers too!

Time to First Byte: What It Is and Why It Matters by Harry Roberts

Harry takes a deep dive into the performance metric of “time to first byte”, or TTFB if you using initialisms that take as long to say as the thing they’re abbreviating.

This makes a great companion piece to Drew’s article on server timing headers.

Thursday, August 8th, 2019

Lazy load embedded YouTube videos - DEV Community 👩‍💻👨‍💻

This is a clever use of the srcdoc attribute on iframes.

Native lazy-loading for the web  |  web.dev

The title is somewhat misleading—currently it’s about native lazy-loading for Chrome, which is not (yet) the web.

I’ve just been adding loading="lazy" to most of the iframes and many of the images on adactio.com, and it’s working a treat …in Chrome.

Priorities

I recently wrote about a web-specific example of a general principle for choosing the right tool for the job:

JavaScript should only do what only JavaScript can do.

I was—yet again—talking about appropriateness. Use the right technology for the task at hand. Here’s the example I gave:

It feels “wrong” when a powerful client-side JavaScript framework is applied to something that could be accomplished using HTML. Making a blog that’s a single page app is over-engineering.

Surprisingly, I got some pushback on this. Šime Vidas wrote:

Based on my experience, this is not necessarily the case.

Going from server-side rendering and progressive enhancement via JS to a single-page app powered by a JS framework was a enormous reduction in complexity for me (so the opposite of over-engineering).

(Emphasis mine.) He goes on to say:

My main concerns are ease of use & maintainability. If you get those things right, you’re good and it’s not over-engineering.

There’s no doubt that maintainability is a desirable goal. And ease of use for the developer is also important …but I think they pale in comparison to ease of use for the end user.

To be fair, the specific use-case I mentioned was making a blog. And a blog is a personal thing. You can do whatever the heck you like on your own website and don’t let anyone tell you otherwise.

So I probably chose a poor example to illustrate my point. I was thinking more about when you’re making websites for a living. You’re being paid money to make something available on the web. In that situation, I strongly believe that user needs should win out over developer convenience.

I wrote about this recently:

As a user-centred developer, my priority is doing what’s best for end users. That’s not to say I don’t value developer convenience. I do. But I prioritise user needs over developer needs. And in any case, those two needs don’t even come into conflict most of the time.

That’s why I responded to Šime, saying:

Your main concern should be user needs—not your own.

When I talk about over-engineering, I’m speaking from the perspective of end users, not developers.

Before considering your ease of use, and maintainability, consider users first.

In fairness to Šime, he’s being very open and honest about his priorities. I admire that. I’ve seen too many developers try to provide user experience justifications for decisions made for developer convenience. Once again I recommend Alex’s excellent article, The “Developer Experience” Bait-and-Switch:

The swap is executed by implying that by making things better for developers, users will eventually benefit equivalently. The unstated agreement is that developers share all of the same goals with the same intensity as end users and even managers. This is not true.

Now I worry I wasn’t specific enough when I talked about choosing appropriate technology:

Appropriateness is something I keep coming back to when it comes to evaluating web technologies. I don’t think there are good tools and bad tools; just tools that are appropriate or inapropriate for the task at hand.

I should have made it clear that I was talking about what is appropriate or inapropriate for users. I think I made the mistake of assuming that this was obvious, and didn’t need saying. I’ll try not to make that mistake again.

There’s a whole group of tools where this point isn’t even relevant—build tools, task runners, version control …anything that never directly touches the end user; use whatever works for you. But if you’re making decisions around HTML, ARIA, CSS, or JavaScript, then appropriateness for the end user should take precedence.

If you’re in that situation—you are being paid money to make websites, and you are making technology decisions—I urge you to remember Charlie’s words: it isn’t about you.

Saturday, August 3rd, 2019

Form design: from zero to hero all in one blog post by Adam Silver

This is about designing forms that everyone can use and complete as quickly as possible. Because nobody actually wants to use your form. They just want the outcome of having used it.

Standard Ebooks: Free and liberated ebooks, carefully produced for the true book lover.

Books in the public domain, lovingly designed and typeset, available in multiple formats for free. Great works of fiction from Austen, Conrad, Stevenson, Wells, Hardy, Doyle, and Dickens, along with classics of non-fiction like Darwin’s The Origin of Species and Shackleton’s South!

Friday, August 2nd, 2019

Seamful Design and Ubicomp Infrastructure (PDF)

Seams:

Seamful design involves deliberately revealing seams to users, and taking advantage of features usually considered as negative or problematic.

Thursday, August 1st, 2019

Navigation preloads in service workers

There’s a feature in service workers called navigation preloads. It’s relatively recent, so it isn’t supported in every browser, but it’s still well worth using.

Here’s the problem it solves…

If someone makes a return visit to your site, and the service worker you installed on their machine isn’t active yet, the service worker boots up, and then executes its instructions. If those instructions say “fetch the page from the network”, then you’re basically telling the browser to do what it would’ve done anyway if there were no service worker installed. The only difference is that there’s been a slight delay because the service worker had to boot up first.

  1. The service worker activates.
  2. The service worker fetches the file.
  3. The service worker does something with the response.

It’s not a massive performance hit, but it’s still a bit annoying. It would be better if the service worker could boot up and still be requesting the page at the same time, like it would do if no service worker were present. That’s where navigation preloads come in.

  1. The service worker activates while simultaneously requesting the file.
  2. The service worker does something with the response.

Navigation preloads—like the name suggests—are only initiated when someone navigates to a URL on your site, either by following a link, or a bookmark, or by typing a URL directly into a browser. Navigation preloads don’t apply to requests made by a web page for things like images, style sheets, and scripts. By the time a request is made for one of those, the service worker is already up and running.

To enable navigation preloads, call the enable() method on registration.navigationPreload during the activate event in your service worker script. But first do a little feature detection to make sure registration.navigationPreload exists in this browser:

if (registration.navigationPreload) {
  addEventListener('activate', activateEvent => {
    activateEvent.waitUntil(
      registration.navigationPreload.enable()
    );
  });
}

If you’ve already got event listeners on the activate event, that’s absolutely fine: addEventListener isn’t exclusive—you can use it to assign multiple tasks to the same event.

Now you need to make use of navigation preloads when you’re responding to fetch events. So if your strategy is to look in the cache first, there’s probably no point enabling navigation preloads. But if your default strategy is to fetch a page from the network, this will help.

Let’s say your current strategy for handling page requests looks like this:

addEventListener('fetch', fetchEvent => {
  const request = fetchEvent.request;
  if (request.headers.get('Accept').includes('text/html')) {
    fetchEvent.respondWith(
      fetch(request)
      .then( responseFromFetch => {
        // maybe cache this response for later here.
        return responseFromFetch;
      })
      .catch( fetchError => {
        return caches.match(request)
        .then( responseFromCache => {
          return responseFromCache || caches.match('/offline');
        });
      })
    );
  }
});

That’s a fairly standard strategy: try the network first; if that doesn’t work, try the cache; as a last resort, show an offline page.

It’s that first step (“try the network first”) that can benefit from navigation preloads. If a preload request is already in flight, you’ll want to use that instead of firing off a new fetch request. Otherwise you’re making two requests for the same file.

To find out if a preload request is underway, you can check for the existence of the preloadResponse promise, which will be made available as a property of the fetch event you’re handling:

fetchEvent.preloadResponse

If that exists, you’ll want to use it instead of fetch(request).

if (fetchEvent.preloadResponse) {
  // do something with fetchEvent.preloadResponse
} else {
  // do something with fetch(request)
}

You could structure your code like this:

addEventListener('fetch', fetchEvent => {
  const request = fetchEvent.request;
  if (request.headers.get('Accept').includes('text/html')) {
    if (fetchEvent.preloadResponse) {
      fetchEvent.respondWith(
        fetchEvent.preloadResponse
        .then( responseFromPreload => {
          // maybe cache this response for later here.
          return responseFromPreload;
        })
        .catch( preloadError => {
          return caches.match(request)
          .then( responseFromCache => {
            return responseFromCache || caches.match('/offline');
          });
        })
      );
    } else {
      fetchEvent.respondWith(
        fetch(request)
        .then( responseFromFetch => {
          // maybe cache this response for later here.
          return responseFromFetch;
        })
        .catch( fetchError => {
          return caches.match(request)
          .then( responseFromCache => {
            return responseFromCache || caches.match('/offline');
          });
        })
      );
    }
  }
});

But that’s not very DRY. Your logic is identical, regardless of whether the response is coming from fetch(request) or from fetchEvent.preloadResponse. It would be better if you could minimise the amount of duplication.

One way of doing that is to abstract away the promise you’re going to use into a variable. Let’s call it retrieve. If a preload is underway, we’ll assign it to that variable:

let retrieve;
if (fetchEvent.preloadResponse) {
  retrieve = fetchEvent.preloadResponse;
}

If there is no preload happening (or this browser doesn’t support it), assign a regular fetch request to the retrieve variable:

let retrieve;
if (fetchEvent.preloadResponse) {
  retrieve = fetchEvent.preloadResponse;
} else {
  retrieve = fetch(request);
}

If you like, you can squash that into a ternary operator:

const retrieve = fetchEvent.preloadResponse ? fetchEvent.preloadResponse : fetch(request);

Use whichever syntax you find more readable.

Now you can apply the same logic, regardless of whether retrieve is a preload navigation or a fetch request:

addEventListener('fetch', fetchEvent => {
  const request = fetchEvent.request;
  if (request.headers.get('Accept').includes('text/html')) {
    const retrieve = fetchEvent.preloadResponse ? fetchEvent.preloadResponse : fetch(request);
    fetchEvent.respondWith(
      retrieve
      .then( responseFromRetrieve => {
        // maybe cache this response for later here.
       return responseFromRetrieve;
      })
      .catch( fetchError => {
        return caches.match(request)
        .then( responseFromCache => {
          return responseFromCache || caches.match('/offline');
        });
      })
    );
  }
});

I think that’s the least invasive way to update your existing service worker script to take advantage of navigation preloads.

Like I said, preload navigations can give a bit of a performance boost if you’re using a network-first strategy. That’s what I’m doing here on adactio.com and on thesession.org so I’ve updated their service workers to take advantage of navigation preloads. But on Resilient Web Design, which uses a cache-first strategy, there wouldn’t be much point enabling navigation preloads.

Jeff Posnick made this point in his write-up of bringing service workers to Google search:

Adding a service worker to your web app means inserting an additional piece of JavaScript that needs to be loaded and executed before your web app gets responses to its requests. If those responses end up coming from a local cache rather than from the network, then the overhead of running the service worker is usually negligible in comparison to the performance win from going cache-first. But if you know that your service worker always has to consult the network when handling navigation requests, using navigation preload is a crucial performance win.

Oh, and those browsers that don’t yet support navigation preloads? No problem. It’s a progressive enhancement. Everything still works just like it did before. And having a service worker on your site in the first place is itself a progressive enhancement. So enabling navigation preloads is like a progressive enhancement within a progressive enhancement. It’s progressive enhancements all the way down!

By the way, if all of this service worker stuff sounds like gibberish, but you wish you understood it, I think my book, Going Offline, will prove quite valuable.

The web without the web - DEV Community 👩‍💻👨‍💻

I love React. I love how server side rendering React apps is trivial because it all compiles down to vanilla HTML rather than web components, effectively turning it into a kickass template engine that can come alive. I love the way you can very effectively still do progressive enhancement by using completely semantic markup and then letting hydration do more to it.

I also hate React. I hate React because these behaviours are not defaults. React is not gonna warn you if you make a form using divs and unlabelled textboxes and send the whole thing to a server. I hate React because CSS-in-JS approaches by default encourage you to write completely self contained one off components rather than trying to build a website UI up as a whole. I hate the way server side rendering and progressive enhancement are not defaults, but rather things you have to go out of your way to do.

An absolutely brilliant post by Laura on how the priorites baked into JavaScript tools like React are really out of whack. They’ll make sure your behind-the-scenes code is super clean, but not give a rat’s ass for the quality of the output that users have to interact with.

And if you want to adjust the front-end code, you’ve got to set up all this tooling just to change a div to a button. That’s quite a barrier to entry.

In elevating frontend to the land of Serious Code we have not just made things incredibly over-engineered but we have also set fire to all the ladders that we used to get up here in the first place.

AMEN!

I love React because it lets me do my best work faster and more easily. I hate React because the culture around it more than the library itself actively prevents other people from doing their best work.

Ooops, I guess we’re full-stack developers now.

Chris broke both his arms just to avoid speaking at the JAMstack conference in London. Seems a bit extreme to me.

Anyway, to make up for not being there, he made a website of his talk. It’s good stuff, tackling the split.

It’s cool to see the tech around our job evolve to the point that we can reach our arms around the whole thing. It’s worthy of some concern when we feel like complication of web technology feels like it’s raising the barrier to entry

Wednesday, July 31st, 2019

The Real Dark Web

Charlie’s thoughts on dev perception:

People speak about “the old guard” and “stupid backwards techniques”, forgetting that it’s real humans, with real constraints who are working on these solutions. Most of us are working in a “stupid backwards way” because that “backwardsness” WORKS. It is something that is proven and is clearly documented. We can implement it confident that it will not disappear from fashion within a couple of years.

Tuesday, July 30th, 2019

Don’t build that app! – Luke Jackson - YouTube

This is a fascinating look at how you can get the benefits of React and npm without using React and npm.

Here’s an accompanying article on the same topic.