Tags: javascript

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Sunday, June 25th, 2017

Service Worker gotchas

A great collection of learned lessons from implementing service workers.

I really, really like it when people share their own personal experiences and “gotchas!” like this.

Thursday, June 8th, 2017

JavaScript Event KeyCodes

A simple little tool for figuring out which keys map to JavaScript keycodes. This’ll save me some googling.

Wednesday, June 7th, 2017

A day without Javascript

Charlie conducts an experiment by living without JavaScript for a day.

So how was it? Well, with just a few minutes of sans-javascript life under my belt, my first impression was “Holy shit, things are fast without javascript”. There’s no ads. There’s no video loading at random times. There’s no sudden interrupts by “DO YOU WANT TO FUCKING SUBSCRIBE?” modals.

As you might expect, lots of sites just don’t work, but there are plenty of sites that work just fine—Google search, Amazon, Wikipedia, BBC News, The New York Times. Not bad!

This has made me appreciate the number of large sites that make the effort to build robust sites that work for everybody. But even on those sites that are progressively enhanced, it’s a sad indictment of things that they can be so slow on the multi-core hyperpowerful Mac that I use every day, but immediately become fast when JavaScript is disabled.

Wednesday, May 31st, 2017

HN PWA - Hacker News readers as Progressive Web Apps

Of all the sites to pick to demo progressive web apps, we get the cesspit that is Hacker News …I guess it is possible to polish a turd.

Anyway, here are some examples of using frameworks to create alternative Hacker News readers. So the challenge here is to display some text to read..

Four of them render absolutely no content without JavaScript.

In the Hall of Shame we have React, Preact, Angular, and Polymer.

In the Hall of Fame, we have the ones doing it right: React, Vue, and Viper.

That’s right: React appears in both. See, it’s not about the tools; it’s about how you use ‘em.

Friday, May 26th, 2017

traintimes.org.uk performance notes

I love, love, *love, traintimes.org.uk—partly because it’s so useful, but also because it’s so fast. I know public transport is the clichéd use-case when it comes to talking about web performance, but in this case it’s genuine: I use the site on trains and in airports.

Matthew gives a blow-by-blow account of the performance optimisations he’s made for the site, including a service worker. The whole thing is a masterclass in performance and progressive enhancement. I’m so glad he took the time to share this!

Tuesday, May 23rd, 2017

Going offline at Indie Web Camp Düsseldorf

I’ve just come back from a ten-day trip to Germany. The trip kicked off with Indie Web Camp Düsseldorf over the course of a weekend.

IndieWebCamp Düsseldorf 2017

Once again the wonderful people at Sipgate hosted us in their beautiful building, and once again myself and Aaron helped facilitate the two days.

IndieWebCamp Düsseldorf 2017

Saturday was the BarCamp-like discussion day. Plenty of interesting topics were covered. I led a session on service workers, and that’s also what I decided to work on for the second day—that’s when the talking is done and we get down to making.

IndieWebCamp Düsseldorf 2017 IndieWebCamp Düsseldorf 2017 IndieWebCamp Düsseldorf 2017 IndieWebCamp Düsseldorf 2017

I like what Ethan is doing on his offline page. He shows a list of pages that have been cached, but instead of just listing URLs, he shows a title and description for each page.

I’ve already got a separate cache for pages that gets added to as the user browses around my site. I needed to figure out a way to store the metadata for those pages so that I could then display it on the offline page. I came up with a workable solution, and interestingly, it involved no changes to the service worker script at all.

When you visit any blog post, I put metadata about the page into localStorage (after first checking that there’s an active service worker):

if (navigator.serviceWorker && navigator.serviceWorker.controller) {
  window.addEventListener('load', function() {
    var data = {
      "title": "A minority report on artificial intelligence",
      "description": "Revisiting Spielberg’s films after a decade and a half.",
      "published": "May 7th, 2017",
      "timestamp": "1494171049"
    };
    localStorage.setItem(
      window.location.href,
      JSON.stringify(data)
    );
  });
}

In my case, I’m outputting the metadata from the server, but you could just as easily grab some from the DOM like this:

var data = {
  "title": document.querySelector("title").innerText,
  "description": document.querySelector("meta[name='description']").getAttribute("contents")
}

Meanwhile in my service worker, when you visit that same page, it gets added to a cache called “pages”. Both localStorage and the cache API are using URLs as keys. I take advantage of that on my offline page.

The nice thing about writing JavaScript on my offline page is that I know the page will only be seen by modern browsers that support service workers, so I can use all sorts of fancy from ES6, or whatever we’re calling it now.

I start by looping through the keys of the “pages” cache (that’s right—the cache API isn’t just for service workers; you can access it from any script). Then I check to see if there is a corresponding localStorage key with the same string (a URL). If there is, I pull the metadata out of local storage and add it to an array called browsingHistory:

const browsingHistory = [];
caches.open('pages')
.then( cache => {
  cache.keys()
  .then(keys => {
    keys.forEach( request => {
      let data = JSON.parse(localStorage.getItem(request.url));
        if (data) {
          data['url'] = request.url;
          browsingHistory.push(data);
      }
    });

Then I sort the list of pages in reverse chronological order:

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

Now I loop through each page in the browsing history list and construct a link to each URL, complete with title and description:

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

Finally I dump the constructed markup into a waiting div in the page with an ID of “history”:

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

All those steps need to be wrapped inside the then clause attached to caches.open("pages") because the cache API is asynchronous.

There you have it. Now if you’re browsing adactio.com and your network connection drops (or my server goes offline), you can choose from a list of pages you’ve previously visited.

The current situation isn’t ideal though. I’ve got a clean-up operation in my service worker to limit the number of items stored in my “pages” cache. The cache never gets bigger than 35 items. But there’s no corresponding clean-up of metadata stored in localStorage. So there could be a lot more bits of metadata in local storage than there are pages in the cache. It’s not harmful, but it’s a bit wasteful.

I can’t do a clean-up of localStorage from my service worker because service workers can’t access localStorage. There’s a very good reason for that: the localStorage API is synchronous, and everything that happens in a service worker needs to be asynchronous.

Service workers can access indexedDB: it’s asynchronous. I could use indexedDB instead of localStorage, but I’m not a masochist. My best bet would be to use the localForage library, which wraps indexedDB in the simple syntax of localStorage.

Maybe I’ll do that at the next Homebrew Website Club here in Brighton.

Monday, May 22nd, 2017

Are we making the web too complicated? | Seldo.Com Blog

Laurie Voss on the trade-off between new powerful web dev tools, and the messiness that abusing those tools can bring:

Is modern web development fearsomely, intimidatingly complicated? Yes, and that’s a problem. Will we make it simpler? Definitely, but probably not as soon as you’d like. Is all this new complexity worthwhile? Absolutely.

I agree that there’s bound to be inappropriate use of technologies, but I don’t agree that we should just accept it:

Are there some people using a huge pile of JavaScript and a monstrous build chain to throw together a single-pager web site with one box that collects an email address? For sure. And that’s silly and unnecessary. But so what? The misuse of technology does not invalidate it.

I think we can raise our standards. Inappropriate use of technology might have been forgivable ten years ago, but if we want web development to be taken seriously as a discipline, I think we should endeavour to use our tools and technologies appropriately.

But we can all agree that the web is a wonderful thing:

Nobody but nobody loves the web more than I do. It’s my baby. And like a child, it’s frustrating to watch it struggle and make mistakes. But it’s amazing to watch it grow up.

Thursday, May 4th, 2017

Going offline. — Ethan Marcotte

Ethan has added a service worker to his site and he’s got a nifty little recipe for showing a list of saved-for-offline articles.

Monday, May 1st, 2017

Offline Web Applications | Udacity

This is a free online video course recorded by Jake a couple of years back. It’s got a really good step-by-step introduction to service workers, delivered in Jake’s typically witty way. Some of the details are a bit out of date, and I must admit that I bailed when it got to IndexedDB, but I highly recommend giving this a go.

There’s also a free course on web accessibility I’m planning to check out.

Springer Nature frontend playbook: house style guide

I like it when organisations share their in-house coding styles. This one from Springer Nature not only has guides for HTML, CSS, and JavaScript, but it also has a good primer on progressive enhancement.

Tuesday, April 25th, 2017

Replacing Disqus with Github Comments · Gazoo.vrv

If you’re using Disqus to power the comments on your blog, you might like to know that it’s pulling on loads of nasty tracking scripts. Bad for privacy and bad for performance.

Tuesday, April 18th, 2017

Offline-first for Your Templated Site (Part Two)

I’m really interested in this idea of service-worker side templating (I know that Glenn is working on something really, really cool in this area too). Can’t wait for part three of this series! (hint, hint, Jeff)

Saturday, April 15th, 2017

Inclusively Hidden | scottohara.me

Comparing different ways to hide content accessibly:

There are three reasons behind hiding content in an interface, and it’s important to identify what those reasons are, as they will correlate with the appropriate technique needed to hide such content.

  1. Temporarily Hidden Content
  2. Purposefully Visually Hidden Content
  3. Purposefully Visual-Only Content

Wednesday, April 12th, 2017

A Todo List

A great step-by-step walkthrough by Heydon of making an accessible to-do list, the “Hello World” of JavaScript frameworks.

There’s a lot of great knowledge in here that can be applied to plenty of other interface elements too.

Thursday, March 30th, 2017

Creating my first HTTP server in node.js | Charlotte Jackson, Front-end developer

Charlotte’s step-by-step account of setting up a Node server is going to be invaluable if and when I get around to dipping my toes in those waters.

Sunday, March 26th, 2017

LA Times and ads | Nelson’s log

A lot has been written about the future of journalism, the importance of businesses like the LA Times being profitable as a way to protect American democracy. I agree with that in theory. But this sort of incompetence and contempt for readers makes me completely uninterested in helping their business.

Like Craig says…

Thursday, March 23rd, 2017

Modern JavaScript for Ancient Web Developers

Speaking as an ancient web developer myself, this account by Gina of her journey into Node.js is really insightful. But I can’t help but get exhausted just contemplating the yak-shaving involved in the tooling set-up:

The sheer number of tools and plugins and packages and dependencies and editor setup and build configurations required to do it “the right way” is enough to stall you before you even get started.

Retrofit Your Website as a Progressive Web App — SitePoint

Turning your existing website into a progressive web “app”—a far more appealing prospect than trying to create an entirely new app-shell architecture:

…they are an enhancement of your existing website which should take no longer than a few hours and have no negative effect on unsupported browsers.

Wednesday, March 22nd, 2017

Improve Your Billing Form’s UX In One Day – Smashing Magazine

A few straightforward steps for improving the usability of credit card forms. The later steps involve JavaScript but the first step uses nothing more than straight-up HTML.

Tuesday, March 21st, 2017

The web share API | Phil Nash

I really need to have a play with this API. I think it could potentially be a useful indie web building block …if the web share target API also gets implemented.