This code only worked in Internet Explorer and in some versions of Safari, but that was plenty of people to befriend. However, MySpace was prepared for this: they also filtered the word javascript from
.
Samy discovered that by inserting a line break into his code, MySpace would not filter out the word javascript. The browser would continue to run the code just fine! Samy had now broken past MySpace’s first line of defence and was able to start running code on his profile page. Now he started looking at what he could do with that code.
alert(document.body.innerHTML)
Samy wondered if he could inspect the page’s source to find the details of other MySpace users to befriend. To do this, you would normally use document.body.innerHTML, but MySpace had filtered this too.
alert(eval('document.body.inne' + 'rHTML'))
This isn’t a problem if you build up JavaScript code inside a string and execute it using the eval() function. This trick also worked with XMLHttpRequest.onReadyStateChange, which allowed Samy to send friend requests to the MySpace API and install the JavaScript code on his new friends’ pages.
One final obstacle stood in his way. The same origin policy is a security mechanism that prevents scripts hosted on one domain interacting with sites hosted on another domain.
if (location.hostname == 'profile.myspace.com') {
document.location = 'http://www.myspace.com'
+ location.pathname + location.search
}
Samy discovered that only the http://www.myspace.com domain would accept his API requests, and requests from http://profile.myspace.com were being blocked by the browser’s same-origin policy. By redirecting the browser to http://www.myspace.com, he discovered that he could load profile pages and successfully make requests to MySpace’s API. Samy installed this code on his profile page, and he waited.
Over the course of the next day, over a million people unwittingly installed Samy’s code into their MySpace profile pages and invited their friends. The load of friend requests on MySpace was so large that the site buckled and shut down. It took them two hours to remove Samy’s code and patch the security holes he exploited. Samy was raided by the United States secret service and sentenced to do 90 days of community service.
This is the power of installing a little bit of JavaScript on someone else’s website. It is called cross site scripting, and its effects can be devastating. It is suspected that cross-site scripting was to blame for the 2018 British Airways breach that leaked the credit card details of 380,000 people.
So how can you help protect yourself from cross-site scripting?
Always sanitise user input when it comes in, using a library such as sanitize-html. Open source tools like this benefit from hundreds of hours of work from dozens of experienced contributors. Don’t be tempted to roll your own protection. MySpace was prepared, but they were not prepared enough. It makes no sense to turn this kind of help down.
You can also use an auto-escaping templating language to make sure nobody else’s HTML can get into your pages. Both Angular and React will do this for you, and they are extremely convenient to use.
You should also implement a content security policy to restrict the domains that content like scripts and stylesheets can be loaded from. Loading content from sites not under your control is a significant security risk, and you should use a CSP to lock this down to only the sources you trust. CSP can also block the use of the eval() function.
For content not under your control, consider setting up sub-resource integrity protection. This allows you to add hashes to stylesheets and scripts you include on your website. Hashes are like fingerprints for digital files; if the content changes, so does the fingerprint. Adding hashes will allow your browser to keep your site safe if the content changes without you knowing.
npm audit: Protecting yourself from code you don’t own
JavaScript and npm run the modern web. Together, they make it easy to take advantage of the world’s largest public registry of open source software. How do you protect yourself from code written by someone you’ve never met? Enter npm audit.
npm audit reviews the security of your website’s dependency tree. You can start using it by upgrading to the latest version of npm:
npm install npm -g
npm audit
When you run npm audit, npm submits a description of your dependencies to the Registry, which returns a report of known vulnerabilities for the packages you have installed.
If your website has a known cross-site scripting vulnerability, npm audit will tell you about it. What’s more, if the vulnerability has been patched, running npm audit fix will automatically install the patched package for you!
Securing your site like it’s 2019
The truth is that since the early days of the web, the stakes of a security breach have become much, much higher. The web is so much more than fandom and mailing DVDs - online banking is now mainstream, social media and dating websites store intimate information about our personal lives, and we are even inviting the internet into our homes.
However, we have powerful new allies helping us stay safe. There are more resources than ever before to teach us how to write secure code. Tools like Angular and React are designed with security features baked-in from the start. We have a new generation of security tools like npm audit to watch over our dependencies.
As we roll over into 2019, let’s take the opportunity to reflect on the security of the code we write and be grateful for the everything we’ve learned in the last twenty years.",2018,Katie Fenn,katiefenn,2018-12-01T00:00:00+00:00,https://24ways.org/2018/securing-your-site-like-its-1999/,code
241,Jank-Free Image Loads,"There are a few fundamental problems with embedding images in pages of hypertext; perhaps chief among them is this: text is very light and loads rather fast; images are much heavier and arrive much later. Consequently, millions (billions?) of times a day, a hapless Web surfer will start reading some text on a page, and then —
Your browser doesn’t support HTML5 video. Here is
a link to the video instead.
— oops! — an image pops in above it, pushing said text down the page, and our poor reader loses their place.
By default, partially-loaded pages have the user experience of a slippery fish, or spilled jar of jumping beans. For the rest of this article, I shall call that jarring, no-good jumpiness by its name: jank. And I’ll chart a path into a jank-free future – one in which it’s easy and natural to author
elements that load like this:
Your browser doesn’t support HTML5 video. Here is
a link to the video instead.
Jank is a very old problem, and there is a very old solution to it: the width and height attributes on
. The idea is: if we stick an image’s dimensions right into the HTML, browsers can know those dimensions before the image loads, and reserve some space on the layout for it so that nothing gets bumped down the page when the image finally arrives.
width
Specifies the intended width of the image in pixels. When given together with the height, this allows user agents to reserve screen space for the image before the image data has arrived over the network.
—The HTML 3.2 Specification, published on January 14 1997
Unfortunately for us, when width and height were first spec’d and implemented, layouts were largely fixed and images were usually only intended to render at their fixed, actual dimensions. When image sizing gets fluid, width and height get weird:
See the Pen fluid width + fixed height = distortion by Eric Portis (@eeeps) on CodePen.
width and height are too rigid for the responsive world. What we need, and have needed for a very long time, is a way to specify fixed aspect ratios, to pair with our fluid widths.
I have good news, bad news, and great news.
The good news is, there are ways to do this, now, that work in every browser. Responsible sites, and responsible developers, go through the effort to do them.
The bad news is that these techniques are all terrible, cumbersome hacks. They’re difficult to remember, difficult to understand, and they can interact with other pieces of CSS in unexpected ways.
So, the great news: there are two on-the-horizon web platform features that are trying to make no-jank, fixed-aspect-ratio, fluid-width images a natural part of the web platform.
aspect-ratio in CSS
The first proposed feature? An aspect-ratio property in CSS!
This would allow us to write CSS like this:
img {
width: 100%;
}
.thumb {
aspect-ratio: 1/1;
}
.hero {
aspect-ratio: 16/9;
}
This’ll work wonders when we need to set aspect ratios for whole classes of images, which are all sized to fit within pre-defined layout slots, like the .thumb and .hero images, above.
Alas, the harder problem, in my experience, is not images with known-ahead-of-time aspect ratios. It’s images – possibly user generated images – that can have any aspect ratio. The really tricky problem is unknown-when-you’re-writing-your-CSS aspect ratios that can vary per-image. Using aspect-ratio to reserve space for images like this requires inline styles:
And inline styles give me the heebie-jeebies! As a web developer of a certain age, I have a tiny man in a blue beanie permanently embedded deep within my hindbrain, who cries out in agony whenever I author a style="""" attribute. And you know what? The old man has a point! By sticking super-high-specificity inline styles in my content, I’m cutting off my, (or anyone else’s) ability to change those aspect ratios, for whatever reason, later.
How might we specify aspect ratios at a lower level? How might we give browsers information about an image’s dimensions, without giving them explicit instructions about how to style it?
I’ll tell you: we could give browsers the intrinsic aspect ratio of the image in our HTML, rather than specifying an extrinsic aspect ratio!
A brief note on intrinsic and extrinsic sizing
What do I mean by “intrinsic” and “extrinsic?”
The intrinsic size of an image is, put simply, how big it’d be if you plopped it onto a page and applied no CSS to it whatsoever. An 800×600 image has an intrinsic width of 800px.
The extrinsic size of an image, then, is how large it ends up after CSS has been applied. Stick a width: 300px rule on that same 800×600 image, and its intrinsic size (accessible via the Image.naturalWidth property, in JavaScript) doesn’t change: its intrinsic size is still 800px. But this image now has an extrinsic size (accessible via Image.clientWidth) of 300px.
It surprised me to learn this year that height and width are interpreted as presentational hints and that they end up setting extrinsic dimensions (albeit ones that, unlike inline styles, have absolutely no specificity).
CSS aspect-ratio lets us avoid setting extrinsic heights and widths – and instead lets us give images (or anything else) an extrinsic aspect ratio, so that as soon as we set one dimension (possibly to a fluid width, like 100%!), the other dimension is set automatically in relation to it.
The last tool I’m going to talk about gets us out of the extrinsic sizing game all together — which, I think, is only appropriate for a feature that we’re going to be using in HTML.
intrinsicsize in HTML
The proposed intrinsicsize attribute will let you do this:
That tells the browser, “hey, this image.jpg that I’m using here – I know you haven’t loaded it yet but I’m just going to let you know right away that it’s going to have an intrinsic size of 800×600.” This gives the browser enough information to reserve space on the layout for the image, and ensures that any and all extrinsic sizing instructions, specified in our CSS, will layer cleanly on top of this, the image’s intrinsic size.
You may ask (I did!): wait, what if my
references multiple resources, which all have different intrinsic sizes? Well, if you’re using srcset, intrinsicsize is a bit of a misnomer – what the attribute will do then, is specify an intrinsic aspect ratio:
In the future (and behind the “Experimental Web Platform Features” flag right now, in Chrome 71+), asking this image for its .naturalWidth would not return 3 – it will return whatever 75vw is, given the current viewport width. And Image.naturalHeight will return that width, divided by the intrinsic aspect ratio: 3/2.
Can’t wait
I seem to have gotten myself into the weeds a bit. Sizing on the web is complicated!
Don’t let all of these details bury the big takeaway here: sometime soon (🤞 2019‽ 🤞), we’ll be able to toss our terrible aspect-ratio hacks into the dustbin of history, get in the habit of setting aspect-ratios in CSS and/or intrinsicsizes in HTML, and surf a less-frustrating, more-performant, less-janky web. I can’t wait!",2018,Eric Portis,ericportis,2018-12-21T00:00:00+00:00,https://24ways.org/2018/jank-free-image-loads/,code
264,Dynamic Social Sharing Images,"Way back when social media was new, you could be pretty sure that whatever you posted would be read by those who follow you. If you’d written a blog post and you wanted to share it with those who follow you, you could post a link and your followers would see it in their streams. Oh heady days!
With so many social channels and a proliferation of content and promotions flying past in everyone’s streams, it’s no longer enough to share content on social media, you have to actively sell it if you want it to be seen. You really need to make the most of every opportunity to catch a reader’s attention if you’re trying to get as many eyes as possible on that sweet, sweet social content.
One of the best ways to grab attention with your posts or tweets is to include an image. There’s heaps of research that says that having images in your posts helps them stand out to followers. Reports I found showed figures from anything from 35% to 150% improvement from just having image in a post. Unfortunately, the details were surrounded with gross words like engagement and visual marketing assets and so I had to close the page before I started to hate myself too much.
So without hard stats to quote, we’ll call it a rule of thumb. The rule of thumb is that posts with images will grab more attention than those without, so it makes sense that when adding pages to a website, you should make sure that they have social media sharing images associated with them.
Adding sharing images
The process for declaring an image to be used in places like Facebook and Twitter is very simple, and at this point is familiar to many of us. You add a meta tag to the head of the page to point to the location of the image to use. When a link to the page is added to a post, the social network will fetch the page, look for the meta tag and then use the image you specified.
There’s a good post on this over at CSS-Tricks if you need to bone up on the details of this and other similar meta tags for social media sharing.
This is all fine and well for content that has a very obvious choice of image to go along with it, but what if you don’t necessarily have an image? One approach is to use stock photography, but that’s not going to be right for every situation.
This was something we faced with 24 ways in 2017. We wanted to add images to the tweets we post each day announcing a new article. Some articles have images, but not all, and there tended not to be any consistency in terms of imagery from one article to the next. We always have an author photograph, but those don’t usually lend themselves directly to being the main ‘hero’ image for an article.
Putting his thinking cap on, Paul came up with a design for an image that used the author photo along with a quote extracted from the article.
One of the hand-made sharing images from 2017
Each day we would pick a quote from the article, and Paul would manually compose an image to be uploaded to the site. The results were great, but the whole process was a bit too labour intensive and relied on an individual (Paul) being available each day to do the work. I thought we could probably improve this.
Hatching a new plan
One initial idea I came up with was to script the image editor to dynamically build a new image by pulling content from our database. Sketch has plugins available to pull JSON content into a design, and our CMS can easily output JSON data, so that was one possibility.
The more I thought about this and how much I wish graphic design tools worked just a little bit more like CSS, the obvious solution hit me. We should just build it with CSS!
In fact, as the author name and image already exist in our CMS, and the visual styling is based on the design of the website, couldn’t this just be another page on the site generated by the CMS?
Breaking it down, I figured the steps needed would be something like:
Create the CSS to lay out a component that could be turned into an image
Add a new field to articles in the CMS to hold a handpicked quote
Build a new article template in the CMS to output the author name and quote dynamically for any article
… um … screenshot?
I thought I’d get cracking and see if I could figure out the final steps later.
Building the page
The first thing to tackle was the basic HTML and CSS to lay out the components for our image. That bit was really easy, as I just asked Paul to do it. Everyone should have a Paul.
Paul’s code uses a fixed dimension container in the HTML, set to 600 × 315px. This is to make it the correct aspect ratio for Facebook’s recommended image size. It’s useful to remember here that it doesn’t need to be responsive or robust, as the page only needs to lay out correctly for a screenshot and a fixed size in a known browser.
With the markup and CSS in place, I turned this into a new template. Our CMS can easily display content through any number of templates, so I created a version of the article template that was totally stripped down. It only included the author details and the quote, along with Paul’s markup.
I also added the quote as a new field on the article in the CMS, so each ‘image’ could be quickly and easily customised in the editing process.
I added a new field to the article template to capture the quote.
With very little effort, we quickly had a page to dynamically generate our ‘image’ right from the CMS. You can see any of them by adding /sharing onto the end of an article URL for any 2018 article.
Our automatically generated layout direct from the CMS
It soon became clear that the elusive Step 4 was going to be the tricky part. I can create a small page on the site that looks like an image, but how should I go about turning it into one? An obvious route is to screenshot the page by hand, but that’s going back to some of the manual steps I was trying to eliminate, and also opens up a possibility for errors to be made. But it did lead me to the thought… how could I automatically take a screenshot?
Enter Puppeteer
Puppeteer is a Node.js library that provides a nice API onto Headless Chrome. What is Headless Chrome, you ask? It’s just a version of the Chrome browser than runs from the command line without ever drawing anything to a user interface window. It loads pages, renders CSS, runs JavaScript, pretty much every normal thing that Chrome on the desktop does, but without a clicky user interface.
Headless Chrome can be used for all sorts of things such as running automated tests on front-end code after making changes, or… get this… rendering pages that can be used for screenshots. The actual process of writing some code to control Chrome and to take the screenshot is where Puppeteer comes in. Puppeteer puts a friendly layer in front of big old scary Chrome to enable us to interact with it using simple JavaScript code running in Node.
Using Puppeteer, I can write a small script that will repeatably turn a URL into an image. So simple is it to do this, that’s it’s actually Puppeteer’s ‘hello world’ example.
First you install Puppeteer. It downloads a compatible headless browser (actually Chromium) as a dependancy, so you don’t need to worry about installing that. At the command line:
npm i puppeteer
Then save a new file as example.js with this code:
const puppeteer = require('puppeteer');
(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://example.com');
await page.screenshot({path: 'example.png'});
await browser.close();
})();
and then run it using Node:
node example.js
This will output an image file example.png to disk, which contains a screenshot of, in this case https://example.com. The logic of the code is reasonably easy to follow:
Launch a browser
Open up a new page
Goto a URL
Take a screenshot
Close the browser
The async function and await keywords are a way to have the script pause and wait for normally asynchronous code to return before proceeding. That’s useful with actions like loading a web page that might take some time to complete. They’re used with Promises, and the effect is to make asynchronous code behave as if it’s synchronous. You can read more about async and await at MDN if you’re interested.
That’s a good proof-of-concept using the basic Puppeteer example. I can take a screenshot of a URL! But what happens if I put the URL of my new special page in there?
Our content is up in the corner of the image with lots of empty space.
That’s not great. It’s okay, but not great. It looks like that, by default, Puppeteer takes a screenshot with a resolution of 800 × 600, so we need to find out how to adjust that. Fortunately, the docs aren’t the worst and I was able to find the page.setViewport() method pretty easily.
const puppeteer = require('puppeteer');
(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://24ways.org/2018/clip-paths-know-no-bounds/sharing');
await page.setViewport({
width: 600,
height: 315
});
await page.screenshot({path: 'example.png'});
await browser.close();
})();
This worked! The screenshot is now 600 × 315 as expected. That’s exactly what we asked for. Trouble is, that’s a bit low res and it is nearly 2019 after all. While in those docs, I noticed the deviceScaleFactor option that can be passed to page.setViewport(). Setting that to 2 gives us an image of the same area of the screen, but with twice as many pixels.
await page.setViewport({
width: 600,
height: 315,
deviceScaleFactor: 2
});
Perfect! We now have a programmatic way of turning a URL into an image.
Improving the script
Rather than having a script with a fixed URL in it that outputs an image called example.png, the next step is to make that a bit more dynamic. The aim here is to have a script that we can run with a URL as an argument and have it output an image for that one page. That way we can run it manually, or hook it into part of our site’s build process to automate the generation of the image.
Our goal is to call the script like this:
node shoot-sharing-image.js https://24ways.org/2018/clip-paths-know-no-bounds/
And I want the image to come out with the name clip-paths-know-no-bounds.png. To do that, I need to have my script look for command arguments, and then to split the URL up to grab the slug from it.
// Get the URL and the slug segment from it
const url = process.argv[2];
const segments = url.split('/');
// Get the second-to-last segment (the slug)
const slug = segments[segments.length-2];
We can then use these variables later in the script, remembering to add sharing back onto the end of the URL to get our dedicated page.
(async () => {
const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto(url + 'sharing');
await page.setViewport({
width: 600,
height: 315,
deviceScaleFactor: 2
});
await page.screenshot({path: slug + '.png'});
await browser.close();
})();
Once you’re generating the image with Node, there’s all sorts of things you can do with it. An obvious step is to move it to the correct location within your site or project.
You can also run optimisations on the file. I’m using imagemin with pngquant to reduce the file size a little.
const imagemin = require('imagemin');
const imageminPngquant = require('imagemin-pngquant');
await imagemin([slug + '.png'], 'build', {
plugins: [
imageminPngquant({quality: '75-90'})
]
});
You can see the completed example as a gist.
Integrating it with your CMS
So we now have a command we can run to take a URL and generate a custom image for that URL. It’s in a format that can be called by any sort of build script, or triggered from a publishing hook in a CMS. Exactly how you do that is going to depend on the way your site is built and the technology stack you’re using, but it’s likely not too hard as long as you can run a command as part of the process.
For 24 ways this year, I’ve been running the script by hand once each article is ready. My script adds the file to a git repo and pushes to a deployment remote that is configured to automatically deploy static assets to our server. Along with our theme of making incremental improvements, next year I’ll look to automate this one step further.
We may also look at having a few slightly different layouts to choose from, so that each day isn’t exactly the same as the last. Interestingly, we could even try some A/B tests to see if there’s any particular format of image or type of quote that does a better job of grabbing attention. There are lots of possibilities!
By using a bit of ingenuity, some custom CMS templates, and the very useful Puppeteer project, we’ve been able to reliably produce dynamic social media sharing images for all of our articles. In doing so, we reduced the dependancy on any individual for producing those images, and opened up a world of possibilities in how we use those images.
I hope you’ll give it a try!",2018,Drew McLellan,drewmclellan,2018-12-24T00:00:00+00:00,https://24ways.org/2018/dynamic-social-sharing-images/,code
256,Develop Your Naturalist Superpowers with Observable Notebooks and iNaturalist,"We’re going to level up your knowledge of what animals you might see in an area at a particular time of year - a skill every naturalist* strives for - using technology! Using iNaturalist and Observable Notebooks we’re going to prototype seasonality graphs for particular species in an area, and automatically create a guide to what animals you might see in each month.
*(a Naturalist is someone who likes learning about nature, not someone who’s a fan of being naked, that’s a ‘Naturist’… different thing!)
Looking for critters in rocky intertidal habitats
One of my favourite things to do is going rockpooling, or as we call it over here in California, ‘tidepooling’. Amounting to the same thing, it’s going to a beach that has rocks where the tide covers then uncovers little pools of water at different times of the day. All sorts of fun creatures and life can be found in this ‘rocky intertidal habitat’
A particularly exciting creature that lives here is the Nudibranch, a type of super colourful ‘sea slug’. There are over 3000 species of Nudibranch worldwide. (The word “nudibranch” comes from the Latin nudus, naked, and the Greek βρανχια / brankhia, gills.)
They are however quite tricky to find! Even though they are often brightly coloured and interestingly shaped, some of them are very small, and in our part of the world in the Bay Area in California their appearance in our rockpools is seasonal. We see them more often in Summer months, despite the not-as-low tides as in our Winter and Spring seasons.
My favourite place to go tidepooling here is Pillar Point in Half Moon bay (at other times of the year more famously known for the surf competition ‘Mavericks’). The rockpools there are rich in species diversity, of varied types and water-coverage habitat zones as well as being relatively accessible.
I was rockpooling at Pillar Point recently with my parents and we talked to a lady who remarked that she hadn’t seen any Nudibranchs on her visit this time. I realised that having an idea of what species to find where, and at what time of year is one of the many superpower goals of every budding Naturalist.
Using technology and the croudsourced species observations of the iNaturalist community we can shortcut our way to this superpower!
Finding nearby animals with iNaturalist
We’re going to be getting our information about what animals you can see in Pillar Point using iNaturalist. iNaturalist is a really fun platform that helps connect people to nature and report their findings of life in the outdoors. It is also a community of nature-loving people who help each other identify and confirm those observations. iNaturalist is a project run as a joint initiative by the California Academy of Sciences and the National Geographic Society.
I’ve been using iNaturalist for over two years to record and identify plants and animals that I’ve found in the outdoors. I use their iPhone app to upload my pictures, which then uses machine learning algorithms to make an initial guess at what it is I’ve seen. The community is really active, and I often find someone else has verified or updated my species guess pretty soon after posting.
This process is great because once an observation has been identified by at least two people it becomes ‘verified’ and is considered research grade. Research grade observations get exported and used by scientists, as well as being indexed by the Global Biodiversity Information Facility, GBIF.
iNaturalist has a great API and API explorer, which makes interacting and prototyping using iNaturalist data really fun. For example, if you go to the API explorer and expand the Observations : Search and fetch section and then the GET /observations API, you get a selection of input boxes that allow you to play with options that you can then pass to the API when you click the ‘Try it out’ button.
You’ll then get a URL that looks a bit like
https://api.inaturalist.org/v1/observations?captive=false &geo=true&verifiable=true&taxon_id=47113&lat=37.495461&lng=-122.499584 &radius=5&order=desc&order_by=created_at
which you can call and interrrogate using a programming language of your choice.
If you would like to see an all-JavaScript application that uses the iNaturalist API, take a look at OwlsNearMe.com which Simon and I built one weekend earlier this year. It gets your location and shows you all iNaturalist observations of owls near you and lists which species you are likely to see (not adjusted for season).
Rapid development using Observable Notebooks
We’re going to be using Observable Notebooks to prototype our examples, pulling data down from iNaturalist. I really like using visual notebooks like Observable, they are great for learning and building things quickly. You may be familiar with Jupyter notebooks for Python which is similar but takes a bit of setup to get going - I often use these for prototyping too. Observable is amazing for querying and visualising data with JavaScript and since it is a hosted product it doesn’t require any setup at all.
You can follow along and play with this example on my Observable notebook. If you create an account there you can fork my notebook and create your own version of this example.
Each ‘notebook’ consists of a page with a column of ‘cells’, similar to what you get in a spreadsheet. A cell can contain Markdown text or JavaScript code and the output of evaluating the cell appears above the code that generated it. There are lots of tutorials out there on Observable Notebooks, I like this code introduction one from Observable (and D3) creator Mike Bostock.
Developing your Naturalist superpowers
If you have an idea of what plants and critters you might see in a place at the time you visit, you can hone in on what you want to study and train your Naturalist eye to better identify the life around you.
For our example, we care about wildlife we can see at Pillar Point, so we need a way of letting the iNaturalist API know which area we are interested in.
We could use a latitide, longitude and radius for this, but a rectangular bounding box is a better shape for the reef. We can use this tool to draw the area we want to search within: boundingbox.klokantech.com
The tool lets you export the bounding box in several forms using the dropdown at the bottom left under the map givese We are going to use the ‘DublinCore’ format as it’s closest to the format needed by the iNaturalist API.
westlimit=-122.50542; southlimit=37.492805; eastlimit=-122.492738; northlimit=37.499811
A quick map primer:
The higher the latitude the more north it is
The lower the latitude the more south it is
Latitude 0 = the equator
The higher the longitude the more east it is of Greenwich
The lower the longitude the more west it is of Greenwich
Longitude 0 = Greenwich
In the iNaturalst API we want to use the parameters nelat, nelng, swlat, swlng to create a query that looks inside a bounding box of Pillar Point near Half Moon Bay in California:
nelat = highest latitude = north limit = 37.499811
nelng = highest longitude = east limit = -122.492738
swlat = smallest latitude = south limit = 37.492805
swlng = smallest longitude = west limit = 122.50542
As API parameters these look like this:
?nelat=37.499811&nelng=-122.492738&swlat=37.492805&swlng=122.50542
These parameters in this format can be used for most of the iNaturalist API methods.
Nudibranch seasonality in Pillar Point
We can use the iNaturalist observation_histogram API to get a count of Nudibranch observations per week-of-year across all time and within our Pillar Point bounding box.
In addition to the geographic parameters that we just worked out, we are also sending the taxon_id of 47113, which is iNaturalists internal number associated with the Nudibranch taxon. By using this we can get all species which are under the parent ‘Order Nudibranchia’.
Another useful piece of naturalist knowledge is understanding the biological classification scheme of Taxanomic Rank - roughly, when a species has a Latin name of two words eg ‘Glaucus Atlanticus’ the first Latin word is the ‘Genus’ like a family name ‘Glaucus’, and the second word identifies that particular species, like a given name ‘Atlanticus’.
The two Latin words together indicate a specific species, the term we use colloquially to refer to a type of animal often differs wildly region to region, and sometimes the same common name in two countries can refer to two different species. The common names for the Glaucus Atlanticus (which incidentally is my favourite sea slug) include: sea swallow, blue angel, blue glaucus, blue dragon, blue sea slug and blue ocean slug! Because this gets super confusing, Scientists like using this Latin name format instead.
The following piece of code asks the iNaturalist Histogram API to return per-week counts for verified observations of Nudibranchs within our Pillar Point bounding box:
pillar_point_counts_per_week = fetch(
""https://api.inaturalist.org/v1/observations/histogram?taxon_id=47113&nelat=37.499811&nelng=-122.492738&swlat=37.492805&swlng=-122.50542&date_field=observed&interval=week_of_year&verifiable=true""
).then(response => {
return response.json();
})
Our next step is to take this data and draw a graph! We’ll be using Vega-Lite for this, which is a fab JavaScript graphing libary that is also easy and fun to use with Observable Notebooks.
(Here is a great tutorial on exploring data and drawing graphs with Observable and Vega-Lite)
The iNaturalist API returns data that looks like this:
{
""total_results"": 53,
""page"": 1,
""per_page"": 53,
""results"": {
""week_of_year"": {
""1"": 136,
""2"": 20,
""3"": 150,
""4"": 65,
""5"": 186,
""6"": 74,
""7"": 47,
""8"": 87,
""9"": 64,
""10"": 56,
But for our Vega-Lite graph we need data that looks like this:
[{
""week"": ""01"",
""value"": 136
}, {
""week"": ""02"",
""value"": 20
}, ...]
We can convert what we get back from the API to the second format using a loop that iterates over the object keys:
objects_to_plot = {
let objects = [];
Object.keys(pillar_point_counts_per_week.results.week_of_year).map(function(week_index) {
objects.push({
week: `Wk ${week_index.toString()}`,
observations: pillar_point_counts_per_week.results.week_of_year[week_index]
});
})
return objects;
}
We can then plug this into Vega-Lite to draw us a graph:
vegalite({
data: {values: objects_to_plot},
mark: ""bar"",
encoding: {
x: {field: ""week"", type: ""nominal"", sort: null},
y: {field: ""observations"", type: ""quantitative""}
},
width: width * 0.9
})
It’s worth noting that we have a lot of observations of Nudibranchs particularly at Pillar Point due in no small part to the intertidal monitoring research that Alison Young and Rebecca Johnson facilitate for the California Achademy of Sciences.
So, what if we want to look for the seasonality of observations of a particular species of adorable sea slug? We want our interface to have a select box with a list of all the species you might find at any time of year. We can do this using the species_counts API to create us an object with the iNaturalist species ID and common & Latin names.
pillar_point_nudibranches = {
let api_results = await fetch(
""https://api.inaturalist.org/v1/observations/species_counts?taxon_id=47113&nelat=37.499811&nelng=-122.492738&swlat=37.492805&swlng=-122.50542&date_field=observed&verifiable=true""
).then(r => r.json())
let species_list = api_results.results.map(i => ({
value: i.taxon.id,
label: `${i.taxon.preferred_common_name} (${i.taxon.name})`
}));
return species_list
}
We can create an interactive select box by importing code from Jeremy Ashkanas’ Observable Notebook: add import {select} from ""@jashkenas/inputs"" to a cell anywhere in our notebook. Observable is magic: like a spreadsheet, the order of the cells doesn’t matter - if one cell is referenced by any other cell then when that cell updates all the other cells refresh themselves. You can also import and reference one notebook from another!
viewof select_species = select({
title: ""Which Nudibranch do you want to see seasonality for?"",
options: [{value: """", label: ""All the Nudibranchs!""}, ...pillar_point_nudibranches],
value: """"
})
Then we go back to our old favourite, the histogram API just like before, only this time we are calling it with the value created by our select box ${select_species} as taxon_id instead of the number 47113.
pillar_point_counts_per_month_per_species = fetch(
`https://api.inaturalist.org/v1/observations/histogram?taxon_id=${select_species}&nelat=37.499811&nelng=-122.492738&swlat=37.492805&swlng=-122.50542&date_field=observed&interval=month_of_year&verifiable=true`
).then(r => r.json())
Now for the fun graph bit! As we did before, we re-format the result of the API into a format compatible with Vega-Lite:
objects_to_plot_species_month = {
let objects = [];
Object.keys(pillar_point_counts_per_month_per_species.results.month_of_year).map(function(month_index) {
objects.push({
month: (new Date(2018, (month_index - 1), 1)).toLocaleString(""en"", {month: ""long""}),
observations: pillar_point_counts_per_month_per_species.results.month_of_year[month_index]
});
})
return objects;
}
(Note that in the above code we are creating a date object with our specific month in, and using toLocalString() to get the longer English name for the month. Because the JavaScript Date object counts January as 0, we use month_index -1 to get the correct month)
And we draw the graph as we did before, only now if you interact with the select box in Observable the graph will dynamically update!
vegalite({
data: {values: objects_to_plot_species_month},
mark: ""bar"",
encoding: {
x: {field: ""month"", type: ""nominal"", sort:null},
y: {field: ""observations"", type: ""quantitative""}
},
width: width * 0.9
})
Now we can see when is the best time of year to plan to go tidepooling in Pillar Point if we want to find a specific species of Nudibranch.
This tool is great for planning when we to go rockpooling at Pillar Point, but what about if you are going this month and want to pre-train your eye with what to look for in order to impress your friends with your knowledge of Nudibranchs?
Well… we can create ourselves a dynamic guide that you can with a list of the species, their photo, name and how many times they have been observed in that month of the year!
Our select box this time looks as follows, simpler than before but assigning the month value to the variable selected_month.
viewof selected_month = select({
title: ""When do you want to see Nudibranchs?"",
options: [
{ label: ""Whenever"", value: """" },
{ label: ""January"", value: ""1"" },
{ label: ""February"", value: ""2"" },
{ label: ""March"", value: ""3"" },
{ label: ""April"", value: ""4"" },
{ label: ""May"", value: ""5"" },
{ label: ""June"", value: ""6"" },
{ label: ""July"", value: ""7"" },
{ label: ""August"", value: ""8"" },
{ label: ""September"", value: ""9"" },
{ label: ""October"", value: ""10"" },
{ label: ""November"", value: ""11"" },
{ label: ""December"", value: ""12"" },
],
value: """"
})
We then can use the species_counts API to get all the relevant information about which species we can see in month=${selected_month}. We’ll be able to reference this response object and its values later with the variable we just created, eg: all_species_data.results[0].taxon.name.
all_species_data = fetch(
`https://api.inaturalist.org/v1/observations/species_counts?taxon_id=47113&month=${selected_month}&nelat=37.499811&nelng=-122.492738&swlat=37.492805&swlng=-122.50542&verifiable=true`
).then(r => r.json())
You can render HTML directly in a notebook cell using Observable’s html tagged template literal:
If you go to Pillar Point ${
{"""": """",
""1"":""in January"",
""2"":""in Febrary"",
""3"":""in March"",
""4"":""in April"",
""5"":""in May"",
""6"":""in June"",
""7"":""in July"",
""8"":""in August"",
""9"":""in September"",
""10"":""in October"",
""11"":""in November"",
""12"":""in December"",
}[selected_month]
} you might see…
${all_species_data.results.map(s => `
${s.taxon.name}
Seen ${s.count} times
`)}
These few lines of HTML are all you need to get this exciting dynamic guide to what Nudibranchs you will see in each month!
Play with it yourself in this Observable Notebook.
Conclusion
I hope by playing with these examples you have an idea of how powerful it can be to prototype using Observable Notebooks and how you can use the incredible crowdsourced community data and APIs from iNaturalist to augment your naturalist skills and impress your friends with your new ‘knowledge of nature’ superpower.
Lastly I strongly encourage you to get outside on a low tide to explore your local rocky intertidal habitat, and all the amazing critters that live there.
Here is a great introduction video to tidepooling / rockpooling, by Rebecca Johnson and Alison Young from the California Academy of Sciences.",2018,Natalie Downe,nataliedowne,2018-12-18T00:00:00+00:00,https://24ways.org/2018/observable-notebooks-and-inaturalist/,code
242,Creating My First Chrome Extension,"Writing a Chrome Extension isn’t as scary at it seems!
Not too long ago, I used a Chrome extension called 20 Cubed. I’m far-sighted, and being a software engineer makes it difficult to maintain distance vision. So I used 20 Cubed to remind myself to look away from my screen and rest my eyes. I loved its simple interface and design. I loved it so much, I often forgot to turn it off in the middle of presentations, where it would take over my entire screen. Oops.
Unfortunately, the developer stopped updating the extension and removed it from Chrome’s extension library. I was so sad. None of the other eye rest extensions out there matched my design aesthetic, so I decided to create my own! Want to do the same?
Fortunately, Google has some respectable documentation on how to create an extension. And remember, Chrome extensions are just HTML, CSS, and JavaScript. You can add libraries and frameworks, or you can just code the “old-fashioned” way. Sky’s the limit!
Setup
But first, some things you’ll need to know about before getting started:
Callbacks
Timeouts
Chrome Dev Tools
Developing with Chrome extension methods requires a lot of callbacks. If you’ve never experienced the joy of callback hell, creating a Chrome extension will introduce you to this concept. However, things can get confusing pretty quickly. I’d highly recommend brushing up on that subject before getting started.
Hyperbole and a Half
Timeouts and Intervals are another thing you might want to brush up on. While creating this extension, I didn’t consider the fact that I’d be juggling three timers. And I probably would’ve saved time organizing those and reading up on the Chrome extension Alarms documentation beforehand. But more on that in a bit.
On the note of organization, abstraction is important! You might have any combination of the following:
The Chrome extension options page
The popup from the Chrome Menu
The windows or tabs you create
The background scripts
And that can get unwieldy. You might also edit the existing tabs or windows in the browser, which you’ll probably want as a separate script too. Note that this tutorial only covers creating your own customized window rather than editing existing windows or tabs.
Alright, now that you know all that up front, let’s get going!
Documentation
TL;DR READ THE DOCS.
A few things to get started:
Read Google’s primer on browser extensions
Have a look at their Getting started tutorial
Check out their overview on Chrome Extensions
This overview discusses the Chrome extension files, architecture, APIs, and communication between pages. Funnily enough, I only discovered the Overview page after creating my extension.
The manifest.json file gives the browser information about the extension, including general information, where to find your extension files and icons, and API permissions required. Here’s what my manifest.json looked like, for example:
https://github.com/jennz0r/eye-rest/blob/master/manifest.json
Because I’m a visual learner, I found the images that describe the extension’s architecture most helpful.
To clarify this diagram, the background.js file is the extension’s event handler. It’s constantly listening for browser events, which you’ll feed to it using the Chrome Extension API. Google says that an effective background script is only loaded when it is needed and unloaded when it goes idle.
The Popup is the little window that appears when you click on an extension’s icon in the Chrome Menu. It consists of markup and scripts, and you can tell the browser where to find it in the manifest.json under page_action: { ""default_popup"": FILE_NAME_HERE }.
The Options page is exactly as it says. This displays customizable options only visible to the user when they either right-click on the Chrome menu and choose “Options” under an extension. This also consists of markup and scripts, and you can tell the browser where to find it in the manifest.json under options_page: FILE_NAME_HERE.
Content scripts are any scripts that will interact with any web windows or tabs that the user has open. These scripts will also interact with any tabs or windows opened by your extension.
Debugging
A quick note: don’t forget the debugging tutorial!
Just like any other Chrome window, every piece of an extension has an inspector and dev tools. If (read: when) you run into errors (as I did), you’re likely to have several inspector windows open – one for the background script, one for the popup, one for the options, and one for the window or tab the extension is interacting with.
For example, I kept seeing the error “This request exceeds the MAX_WRITE_OPERATIONS_PER_HOUR quota.” Well, it turns out there are limitations on how often you can sync stored information.
Another error I kept seeing was “Alarm delay is less than minimum of 1 minutes. In released .crx, alarm “ALARM_NAME_HERE” will fire in approximately 1 minutes”. Well, it turns out there are minimum interval times for alarms.
Chrome Extension creation definitely benefits from debugging skills. Especially with callbacks and listeners, good old fashioned console.log can really help!
Me adding a ton of `console.log`s while trying to debug my alarms.
Eye Rest Functionality
Ok, so what is the extension I created? Again, it’s a way to rest your eyes every twenty minutes for twenty seconds. So, the basic functionality should look like the following:
If the extension is running AND
If the user has not clicked Pause in the Popup HTML AND
If the counter in the Popup HTML is down to 00:00 THEN
Open a new window with Timer HTML AND
Start a 20 sec countdown in Timer HTML AND
Reset the Popup HTML counter to 20:00
If the Timer HTML is down to 0 sec THEN
Close that window. Rinse. Repeat.
Sounds simple enough, but wow, these timers became convoluted! Of all the Chrome extensions I decided to create, I decided to make one that’s heavily dependent on time, intervals, and having those in sync with each other. In other words, I made this unnecessarily complicated and didn’t realize until I started coding.
For visual reference of my confusion, check out the GitHub repository for Eye Rest. (And yes, it’s a pun.)
API
Now let’s discuss the APIs that I used to build this extension.
Alarms
What even are alarms? I didn’t know either.
Alarms are basically Chrome’s setTimeout and setInterval. They exist because, as Google says…
DOM-based timers, such as window.setTimeout() or window.setInterval(), are not honored in non-persistent background scripts if they trigger when the event page is dormant.
For more information, check out this background migration doc.
One interesting note about alarms in Chrome extensions is that they are persistent. Garbage collection with Chrome extension alarms seems unreliable at best. I didn’t have much luck using the clearAll method to remove alarms I created on previous extension loads or installs. A workaround (read: hack) is to specify a unique alarm name every time your extension is loaded and clearing any other alarms without that unique name.
Background Scripts
For Eye Rest, I have two background scripts. One is my actual initializer and event listener, and the other is a helpers file.
I wanted to share a couple of functions between my Background and Popup scripts. Specifically, the clearAndCreateAlarm function. I wanted my background script to clear any existing alarms, create a new alarm, and add remaining time until the next alarm to local storage immediately upon extension load. To make the function available to the Background script, I added helpers.js as the first item under background > scripts in my manifest.json.
I also wanted my Popup script to do the same things when the user has unpaused the extension’s functionality. To make the function available to the Popup script, I just include the helpers script in the Popup HTML file.
Other APIs
Windows
I use the Windows API to create the Timer window when the time of my alarm is up. The window creation is initiated by my Background script.
One day, while coding late into the evening, I found it very confusing that the window.create method included url as an option. I assumed it was meant to be an external web address. A friend pondered that there must be an option to specify the window’s HTML. Until then, it hadn’t dawned on me that the url could be relative. Duh. I was tired!
I pass the timer.html as the url option, as well as type, size, position, and other visual options.
Storage
Maybe you want to pass information back and forth between the Background script and your Popup script? You can do that using Chrome or local storage. One benefit of using local storage over Chrome’s storage is avoiding quotas and write operation maximums.
I wanted to pass the time at which the latest alarm was set, the time to the next alarm, and whether or not the timer is paused between the Background and Popup scripts. Because the countdown should change every second, it’s quite complicated and requires lots of writes. That’s why I went with the user’s local storage. You can see me getting and setting those variables in my Background, Helper, and Popup scripts. Just search for date, nextAlarmTime, and isPaused.
Declarative Content
The Declarative Content API allows you to show your extension’s page action based on several type of matches, without needing to take a host permission or inject a content script. So you’ll need this to get your extension to work in the browser!
You can see me set this in my Background script. Because I want my extension’s popup to appear on every page one is browsing, I leave the page matchers empty.
There are many more APIs for Chrome apps and extensions, so make sure to surf around and see what features are available!
The Extension
Here’s what my original Popup looked like before I added styles.
And here’s what it looks like with new styles. I guess I’m going for a Nickelodeon feel.
And here’s the Timer window and Popup together!
Publishing
Publishing is a cinch. You just zip up your files, create a new or use an existing Google Developer account, upload the files, add some details, and pay a one time $5 fee. That’s all! Then your extension will be available on the Chrome extension store! Neato :D
My extension is now available for you to install.
Conclusion
I thought creating a time based Chrome Extension would be quick and easy. I was wrong. It was more complicated than I thought! But it’s definitely achievable with some time, persistence, and good ole Google searches.
Eventually, I’d like to add more interactive elements to Eye Rest. For example, hitting the YouTube API to grab a silly or cute video as a reward for looking away during the 20 sec countdown and not closing the timer window. This harkens back to one of my first web projects, Toothtimer, from 2012. Or maybe a way to change the background colors of the Timer and Popup!
Either way, with Eye Rest’s framework built out, I’m feeling fearless about future feature adds! Building this Chrome extension took some broken nails, achy shoulders, and tired eyes, but now Eye Rest can tell me to give my eyes a break every 20 minutes.",2018,Jennifer Wong,jenniferwong,2018-12-05T00:00:00+00:00,https://24ways.org/2018/my-first-chrome-extension/,code
257,The (Switch)-Case for State Machines in User Interfaces,"You’re tasked with creating a login form. Email, password, submit button, done.
“This will be easy,” you think to yourself.
Login form by Selecto
You’ve made similar forms many times in the past; it’s essentially muscle memory at this point. You’re working closely with a designer, who gives you a beautiful, detailed mockup of a login form. Sure, you’ll have to translate the pixels to meaningful, responsive CSS values, but that’s the least of your problems.
As you’re writing up the HTML structure and CSS layout and styles for this form, you realize that you don’t know what the successful “logged in” page looks like. You remind the designer, who readily gives it to you. But then you start thinking more and more about how the login form is supposed to work.
What if login fails? Where do those errors show up?
Should we show errors differently if the user forgot to enter their email, or password, or both?
Or should the submit button be disabled?
Should we validate the email field?
When should we show validation errors – as they’re typing their email, or when they move to the password field, or when they click submit? (Note: many, many login forms are guilty of this.)
When should the errors disappear?
What do we show during the login process? Some loading spinner?
What if loading takes too long, or a server error occurs?
Many more questions come up, and you (and your designer) are understandably frustrated. The lack of upfront specification opens the door to scope creep, which readily finds itself at home in all the unexplored edge cases.
Modeling Behavior
Describing all the possible user flows and business logic of an application can become tricky. Ironically, user stories might not tell the whole story – they often leave out potential edge-cases or small yet important bits of information.
However, one important (and very old) mathematical model of computation can be used for describing the behavior and all possible states of a user interface: the finite state machine.
The general idea, as it applies to user interfaces, is that all of our applications can be described (at some level of abstraction) as being in one, and only one, of a finite number of states at any given time. For example, we can describe our login form above in these states:
start - not submitted yet
loading - submitted and logging in
success - successfully logged in
error - login failed
Additionally, we can describe an application as accepting a finite number of events – that is, all the possible events that can be “sent” to the application, either from the user or some other external entity:
SUBMIT - pressing the submit button
RESOLVE - the server responds, indicating that login is successful
REJECT - the server responds, indicating that login failed
Then, we can combine these states and events to describe the transitions between them. That is, when the application is in one state, an an event occurs, we can specify what the next state should be:
From the start state, when the SUBMIT event occurs, the app should be in the loading state.
From the loading state, when the RESOLVE event occurs, login succeeded and the app should be in the success state.
If login fails from the loading state (i.e., when the REJECT event occurs), the app should be in the error state.
From the error state, the user should be able to retry login: when the SUBMIT event occurs here, the app should go to the loading state.
Otherwise, if any other event occurs, don’t do anything and stay in the same state.
That’s a pretty thorough description, similar to a user story! It’s also a bit more symbolic than a user story (e.g., “when the SUBMIT event occurs” instead of “when the user presses the submit button”), and that’s for a reason. By representing states, events, and transitions symbolically, we can visualize what this state machine looks like:
Every state is represented by a box, and every event is connected to a transition arrow that connects two states. This makes it intuitive to follow the flow and understand what the next state should be given the current state and an event.
From Visuals to Code
Drawing a state machine doesn’t require any special software; in fact, using paper and pencil (in case anything changes!) does the job quite nicely. However, one common problem is handoff: it doesn’t matter how detailed a user story or how well-designed a visualization is, it eventually has to be coded in order for it to become part of a real application.
With the state machine model described above, the same visual description can be mapped directly to code. Traditionally, and as the title suggests, this is done using switch/case statements:
function loginMachine(state, event) {
switch (state) {
case 'start':
if (event === 'SUBMIT') {
return 'loading';
}
break;
case 'loading':
if (event === 'RESOLVE') {
return 'success';
} else if (event === 'REJECT') {
return 'error';
}
break;
case 'success':
// Accept no further events
break;
case 'error':
if (event === 'SUBMIT') {
return 'loading';
}
break;
default:
// This should never occur
return undefined;
}
}
console.log(loginMachine('start', 'SUBMIT'));
// => 'loading'
This is fine (I suppose) but personally, I find it much easier to use objects:
const loginMachine = {
initial: ""start"",
states: {
start: {
on: { SUBMIT: 'loading' }
},
loading: {
on: {
REJECT: 'error',
RESOLVE: 'success'
}
},
error: {
on: {
SUBMIT: 'loading'
}
},
success: {}
}
};
function transition(state, event) {
return machine
.states[state] // Look up the state
.on[event] // Look up the next state based on the event
|| state; // If not found, return the current state
}
console.log(transition('start', 'SUBMIT'));
As you might have noticed, the loginMachine is a plain JS object, and can be written in JSON. This is important because it allows the machine to be visualized by a 3rd-party tool, as demonstrated here:
A Common Language Between Designers and Developers
Although finite state machines are a fundamental part of computer science, they have an amazing potential to bridge the application specification gap between designers and developers, as well as project managers, stakeholders, and more. By designing a state machine visually and with code, designers and developers alike can:
identify all possible states, and potentially missing states
describe exactly what should happen when an event occurs on a given state, and prevent that event from having unintended side-effects in other states (ever click a submit button more than once?)
eliminate impossible states and identify states that are “unreachable” (have no entry transition) or “sunken” (have no exit transition)
add features with full confidence of knowing what other states it might affect
simplify redundant states or complex user flows
create test paths for almost every possible user flow, and easily identify edge cases
collaborate better by understanding the entire application model equally.
Not a New Idea
I’m not the first to suggest that state machines can help bridge the gap between design and development.
Vince MingPu Shao wrote an article about designing UI states and communicating with developers effectively with finite state machines
User flow diagrams, which visually describe the paths that a user can take through an app to achieve certain goals, are essentially state machines. Numerous tools, from Sketch plugins to standalone apps, exist for creating them.
In 1999, Ian Horrocks wrote a book titled “Constructing the User Interface with Statecharts”, which takes state machines to the next level and describes the inherent difficulties (and solutions) with creating complex UIs. The ideas in the book are still relevant today.
More than a decade earlier, David Harel published “Statecharts: A Visual Formalism for Complex Systems”, in which the statechart - an extended hierarchical state machine model - is born.
State machines and statecharts have been used for complex systems and user interfaces, both physical and digital, for decades, and are especially prevalent in other industries, such as game development and embedded electronic systems. Even NASA uses statecharts for the Curiosity Rover and more, citing many benefits:
Visualized modeling
Precise diagrams
Automatic code generation
Comprehensive test coverage
Accommodation of late-breaking requirements changes
Moving Forward
It’s time that we improve how we communicate between designers and developers, much less improve the way we develop UIs to deliver the best, bug-free, optimal user experience. There is so much more to state machines and statecharts than just being a different way of designing and coding. For more resources:
The World of Statecharts is a comprehensive guide by Erik Mogensen in using statecharts in your applications
The Statechart Community on Spectrum is always full of interesting ideas and questions related to state machines, statecharts, and software modeling
I gave a talk at React Rally over a year ago about how state machines (finite automata) can improve the way we develop applications. The latest one is from Reactive Conf, where I demonstrate how statecharts can be used to automatically generate test cases.
I have also been working on XState, which is a library for “state machines and statecharts for the modern web”. You can create and visualize statecharts in JavaScript, and use them in any framework (and soon enough, multiple different languages).
I’m excited about the future of developing web and mobile applications with statecharts, especially with regard to faster design/development cycles, auto-generated testing, better error prevention, comprehensive analytics, and even the use of model-based reinforcement learning and artificial intelligence to greatly improve the user experience.",2018,David Khourshid,davidkhourshid,2018-12-12T00:00:00+00:00,https://24ways.org/2018/state-machines-in-user-interfaces/,code