Tags: list

158

sparkline

Friday, October 23rd, 2020

This page is a truly naked, brutalist html quine.

I think this is quite beautiful—no need to view source; the style sheet is already in the document.

Wednesday, October 14th, 2020

Saving forms

I added a long-overdue enhancement to The Session recently. Here’s the scenario…

You’re on a web page with a comment form. You type your well-considered thoughts into a textarea field. But then something happens. Maybe you accidentally navigate away from the page or maybe your network connection goes down right when you try to submit the form.

This is a textbook case for storing data locally on the user’s device …at least until it has safely been transmitted to the server. So that’s what I set about doing.

My first decision was choosing how to store the data locally. There are multiple APIs available: sessionStorage, IndexedDB, localStorage. It was clear that sessionStorage wasn’t right for this particular use case: I needed the data to be saved across browser sessions. So it was down to IndexedDB or localStorage. IndexedDB is the more versatile and powerful—because it’s asynchronous—but localStorage is nice and straightforward so I decided on that. I’m not sure if that was the right decision though.

Alright, so I’m going to store the contents of a form in localStorage. It accepts key/value pairs. I’ll make the key the current URL. The value will be the contents of that textarea. I can store other form fields too. Even though localStorage technically only stores one value, that value can be a JSON object so in reality you can store multiple values with one key (just remember to parse the JSON when you retrieve it).

Now I know what I’m going to store (the textarea contents) and how I’m going to store it (localStorage). The next question is when should I do it?

I could play it safe and store the comment whenever the user presses a key within the textarea. But that seems like overkill. It would be more efficient to only save when the user leaves the current page for any reason.

Alright then, I’ll use the unload event. No! Bad Jeremy! If I use that then the browser can’t reliably add the current page to the cache it uses for faster back-forwards navigations. The page life cycle is complicated.

So beforeunload then? Well, maybe. But modern browsers also support a pagehide event that looks like a better option.

In either case, just adding a listener for the event could screw up the caching of the page for back-forwards navigations. I should only listen for the event if I know that I need to store the contents of the textarea. And in order to know if the user has interacted with the textarea, I’m back to listening for key presses again.

But wait a minute! I don’t have to listen for every key press. If the user has typed anything, that’s enough for me. I only need to listen for the first key press in the textarea.

Handily, addEventListener accepts an object of options. One of those options is called “once”. If I set that to true, then the event listener is only fired once.

So I set up a cascade of event listeners. If the user types anything into the textarea, that fires an event listener (just once) that then adds the event listener for when the page is unloaded—and that’s when the textarea contents are put into localStorage.

I’ve abstracted my code into a gist. Here’s what it does:

  1. Cut the mustard. If this browser doesn’t support localStorage, bail out.
  2. Set the localStorage key to be the current URL.
  3. If there’s already an entry for the current URL, update the textarea with the value in localStorage.
  4. Write a function to store the contents of the textarea in localStorage but don’t call the function yet.
  5. The first time that a key is pressed inside the textarea, start listening for the page being unloaded.
  6. When the page is being unloaded, invoke that function that stores the contents of the textarea in localStorage.
  7. When the form is submitted, remove the entry in localStorage for the current URL.

That last step isn’t something I’m doing on The Session. Instead I’m relying on getting something back from the server to indicate that the form was successfully submitted. If you can do something like that, I’d recommend that instead of listening to the form submission event. After all, something could still go wrong between the form being submitted and the data being received by the server.

Still, this bit of code is better than nothing. Remember, it’s intended as an enhancement. You should be able to drop it into any project and improve the user experience a little bit. Ideally, no one will ever notice it’s there—it’s the kind of enhancement that only kicks in when something goes wrong. A little smidgen of resilient web design. A defensive enhancement.

Wednesday, August 26th, 2020

Submitting a form with datalist

I’m a big fan of HTML5’s datalist element and its elegant design. It’s a way to progressively enhance any input element into a combobox.

You use the list attribute on the input element to point to the ID of the associated datalist element.

<label for="homeworld">Your home planet</label>
<input type="text" name="homeworld" id="homeworld" list="planets">
<datalist id="planets">
 <option value="Mercury">
 <option value="Venus">
 <option value="Earth">
 <option value="Mars">
 <option value="Jupiter">
 <option value="Saturn">
 <option value="Uranus">
 <option value="Neptune">
</datalist>

It even works on input type="color", which is pretty cool!

The most common use case is as an autocomplete widget. That’s how I’m using it over on The Session, where the datalist is updated via Ajax every time the input is updated.

But let’s stick with a simple example, like the list of planets above. Suppose the user types “jup” …the datalist will show “Jupiter” as an option. The user can click on that option to automatically complete their input.

It would be handy if you could automatically submit the form when the user chooses a datalist option like this.

Well, tough luck.

The datalist element emits no events. There’s no way of telling if it has been clicked. This is something I’ve been trying to find a workaround for.

I got my hopes up when I read Amber’s excellent article about document.activeElement. But no, the focus stays on the input when the user clicks on an option in a datalist.

So if I can’t detect whether a datalist has been used, this best I can do is try to infer it. I know it’s not exactly the same thing, and it won’t be as reliable as true detection, but here’s my logic:

  • Keep track of the character count in the input element.
  • Every time the input is updated in any way, check the current character count against the last character count.
  • If the difference is greater than one, something interesting happened! Maybe the user pasted a value in …or maybe they used the datalist.
  • Loop through each of the options in the datalist.
  • If there’s an exact match with the current value of the input element, chances are the user chose that option from the datalist.
  • So submit the form!

Here’s how that translates into DOM scripting code:

document.querySelectorAll('input[list]').forEach( function (formfield) {
  var datalist = document.getElementById(formfield.getAttribute('list'));
  var lastlength = formfield.value.length;
  var checkInputValue = function (inputValue) {
    if (inputValue.length - lastlength > 1) {
      datalist.querySelectorAll('option').forEach( function (item) {
        if (item.value === inputValue) {
          formfield.form.submit();
        }
      });
    }
    lastlength = inputValue.length;
  };
  formfield.addEventListener('input', function () {
    checkInputValue(this.value);
  }, false);
});

I’ve made a gist with some added feature detection and mustard-cutting at the start. You should be able to drop it into just about any page that’s using datalist. It works even if the options in the datalist are dynamically updated, like the example on The Session.

It’s not foolproof. The inference relies on the difference between what was previously typed and what’s autocompleted to be more than one character. So in the planets example, if someone has type “Jupite” and then they choose “Jupiter” from the datalist, the form won’t automatically submit.

But still, I reckon it covers most common use cases. And like the datalist element itself, you can consider this functionality a progressive enhancement.

Wednesday, August 19th, 2020

radEventListener: a Tale of Client-side Framework Performance | CSS-Tricks

Excellent research by Jeremy Wagner comparing the performance impact of React, Preact, and vanilla JavaScript. The results are simultaneously shocking and entirely unsurprising.

Sunday, August 16th, 2020

Solid Start

A four-point checklist for inclusive design:

Are you a person that makes digital things for other people? Awesome—because this page is all about making things for people. There are four ways you can improve your creation for everybody. All four are testable, fixable and they improve usability for everybody.

Saturday, July 11th, 2020

A little bit of plain Javascript can do a lot

I decided to implement almost all of the UI by just adding & removing CSS classes, and using CSS transitions if I want to animate a transition.

Yup. It’s remarkable how much can be accomplished with that one DOM scripting pattern.

I was pretty surprised by how much I could get done with just plain JS. I ended up writing about 50 lines of JS to do everything I wanted to do.

Thursday, June 25th, 2020

Top 10 books about remaking the future | Peter F Hamilton | Books | The Guardian

Here then are 10 stories of remaking the future that contain hope — or at least stability.

  1. The City and the Stars by Arthur C Clarke
  2. The First Fifteen Lives of Harry August by Claire North
  3. Revenger by Alastair Reynolds
  4. Children of Time by Adrian Tchaikovsky
  5. Do You Dream of Terra-Two? by Temi Oh
  6. Consider Phlebas by Iain M Banks
  7. Natural History by Justina Robson
  8. Ancillary Justice by Ann Leckie
  9. Way Station by Clifford D Simak
  10. News from Gardenia by Robert Llewellyn

Tuesday, May 26th, 2020

Responsive web design turns ten. — Ethan Marcotte

2010 was quite a year:

And exactly three weeks after Jeremy Keith’s HTML5 For Web Designers was first published, “Responsive Web Design” went live in A List Apart.

Nothing’s been quite the same since.

I remember being at that An Event Apart in Seattle where Ethan first unveiled the phrase and marvelling at how well everything just clicked into place, perfectly capturing the zeitgeist. I was in. 100%.

Thursday, April 23rd, 2020

Limiting input type=”color” to a certain palette (from an image) | Christian Heilmann

I never thought of combining the datalist element with input type="color"—it’s pretty cool that it just works!

Thursday, April 16th, 2020

It was 20 years ago today… - Web Directions

John’s article, A Dao Of Web Design, is twenty years old. If anything, it’s more relevant today than when it was written.

Here, John looks back on those twenty years, and forward to the next twenty…

Monday, March 30th, 2020

HTML DOM - Common tasks of managing HTML DOM with vanilla JavaScript

This is a great way to organise code snippets—listed by use case, and searchable too!

Next time you’re stuck on some DOM scripting, before reaching for a framework or library, check here first.

To-Do Terrarium

I love this little to-do app! Every time you tick something off your list, something grows in your virtual terrarium. Lovely!

Monday, March 23rd, 2020

Accessible HTML Elements | Amber’s Website

Amber runs through some HTML elements that help you provide semantic information—and accessibility—for your website: headings, paragraphs, lists, and more:

You may be aware that ARIA roles are often used with HTML elements. I haven’t written about them here, as it’s good to see how HTML written without ARIA can still be accessible.

Saturday, March 7th, 2020

A Guide to Handling Browser Events by Sarah Chima - Front-End Developer

This is a great step-by-step explanation of event handling in JavaScript!

Saturday, February 15th, 2020

Standards for Writing Accessibly – A List Apart

  • Write Chronologically, Not Spatially
  • Write Left to Right, Top to Bottom
  • Don’t Use Colors and Icons Alone
  • Describe the Action, Not the Behavior

Thursday, November 21st, 2019

Request with Intent: Caching Strategies in the Age of PWAs – A List Apart

Aaron outlines some sensible strategies for serving up images, including using the Cache API from your service worker script.

Sunday, November 17th, 2019

Responsible JavaScript: Part III – A List Apart

This chimes nicely with my recent post on third-party scripts. Here, Jeremy treats third-party JavaScript at technical debt and outlines some solutions to staying on top of it.

Convenience always has a price, and the web is wracked by our collective preference for it. JavaScript, in particular, is employed in a way that suggests a rapidly increasing tendency to outsource whatever it is that We (the first party) don’t want to do. At times, this is a necessary decision; it makes perfect financial and operational sense in many situations.

But make no mistake, third-party JavaScript is never cheap. It’s a devil’s bargain where vendors seduce you with solutions to your problem, yet conveniently fail to remind you that you have little to no control over the side effects that solution introduces.

Tuesday, November 5th, 2019

Become a Front-End Master in 2020 With These 10 Project Ideas | CSS-Tricks

The title sounds clickbaity, but this is a thoughtful list of project ideas from Chris (partly prompted by the way other lists seem to involve nothing but JavaScript frameworks).

Wednesday, October 16th, 2019

The lines of code that changed everything.

We construct top-10 lists for movies, games, TV—pieces of work that shape our souls. But we don’t sit around compiling lists of the world’s most consequential bits of code, even though they arguably inform the zeitgeist just as much.

This is a fascinating way to look at the history of computing, by focusing in on culturally significant pieces of code. The whole list is excellent, but if I had to pick a favourite …well, see if you can guess what it is.

Thursday, October 3rd, 2019

A Modern CSS Reset - Andy Bell

Some very smart ideas in here for resetting default browser styles, like only resetting lists that have classes applied to them:

ul[class],
ol[class] {
  padding: 0;
}

I select only lists that do have a class attribute because if a plain ol’ <ul> or <ol> gets used, I want it to look like a list. A lot of resets, including my previous ones, aggressively remove that.