Tags: dom

185

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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.

Saturday, August 1st, 2020

this vs that - What is the difference between ___ and ___ in the front-end development?

A handy reference for explaining the differences between confusingly similar bits of HTML, CSS, and JavaScript.

Sunday, July 19th, 2020

90s Festival Generator

I spent far too long hitting refresh and then clicking on the names of some of the Irish bands down near the bottom of the line-up.

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.

Tuesday, July 7th, 2020

Custom properties

I made the website for the Clearleft podcast last week. The design is mostly lifted straight from the rest of the Clearleft website. The main difference is the masthead. If the browser window is wide enough, there’s a background image on the right hand side.

I mostly added that because I felt like the design was a bit imbalanced without something there. On the home page, it’s a picture of me. Kind of cheesy. But the image can be swapped out. On other pages, there are different photos. All it takes is a different class name on that masthead.

I thought about having the image be completely random (and I still might end up doing this). I’d need to use a bit of JavaScript to choose a class name at random from a list of possible values. Something like this:

var names = ['jeremy','katie','rich','helen','trys','chris'];
var name = names[Math.floor(Math.random() * names.length)];
document.querySelector('.masthead').classList.add(name);

(You could paste that into the dev tools console to see it in action on the podcast site.)

Then I read something completely unrelated. Cassie wrote a fantastic article on her site called Making lil’ me - part 1. In it, she describes how she made the mouse-triggered animation of her avatar in the footer of her home page.

It’s such a well-written technical article. She explains the logic of what she’s doing, and translates that logic into code. Then, after walking you through the native code, she shows how you could use the Greeksock library to achieve the same effect. That’s the way to do it! Instead of saying, “Here’s a library that will save you time—don’t worry about how it works!”, she’s saying “Here’s it works without a library; here’s how it works with a library; now you can make an informed choice about what to use.” It’s a very empowering approach.

Anyway, in the article, Cassie demonstrates how you can use custom properties as a bridge between JavaScript and CSS. JavaScript reads the mouse position and updates some custom properties accordingly. Those same custom properties are used in CSS for positioning. Voila! Now you’ve got the position of an element responding to mouse movements.

That’s what made me think of the code snippet I wrote above to update a class name from JavaScript. I automatically thought of updating a class name because, frankly, that’s how I’ve always done it. I’d say about 90% of the DOM scripting I’ve ever done involves toggling the presence of class values: accordions, fly-out menus, tool-tips, and other progressive disclosure patterns.

That’s fine. But really, I should try to avoid touching the DOM at all. It can have performance implications, possibly triggering unnecessary repaints and reflows.

Now with custom properties, there’s a direct line of communication between JavaScript and CSS. No need to use the HTML as a courier.

This made me realise that I need to be aware of automatically reaching for a solution just because that’s the way I’ve done something in the past. I should step back and think about the more efficient solutions that are possible now.

It also made me realise that “CSS variables” is a very limiting way of thinking about custom properties. The fact that they can be updated in real time—in CSS or JavaScript—makes them much more powerful than, say, Sass variables (which are more like constants).

But I too have been guilty of underselling them. I almost always refer to them as “CSS custom properties” …but a lot of their potential comes from the fact that they’re not confined to CSS. From now on, I’m going to try calling them custom properties, without any qualification.

We need more inclusive web performance metrics | Filament Group, Inc.

Good point. When we talk about perceived performance, the perception in question is almost always visual. We should think more inclusively than that.

Wednesday, June 17th, 2020

Where did the focus go? | Amber’s Website

Amber documents a very handy bit of DOM scripting when it comes to debugging focus management: document.activeElement.

Wednesday, May 13th, 2020

Reef

This micro libarary does DOM diffing in native JavaScript:

Reef is an anti-framework.

It does a lot less than the big guys like React and Vue. It doesn’t have a Virtual DOM. It doesn’t require you to learn a custom templating syntax. It doesn’t provide a bunch of custom methods.

Reef does just one thing: render UI.

Sunday, May 10th, 2020

Getting Started with the DOM

Here’s a short clear introduction to DOM scripting.

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.

Tuesday, March 17th, 2020

Scripts: async, defer

I’m constantly forgetting the difference between the async attribute and the defer attribute on script elements—this is a handy explanation.

Wednesday, March 11th, 2020

The History of the URL

This is a wonderful deep dive into all the parts of a URL:

scheme:[//[user:password@]host[:port]][/]path[?query][#fragment]

There’s a lot of great DNS stuff about the host part:

Root DNS servers operate in safes, inside locked cages. A clock sits on the safe to ensure the camera feed hasn’t been looped. Particularily given how slow DNSSEC implementation has been, an attack on one of those servers could allow an attacker to redirect all of the Internet traffic for a portion of Internet users. This, of course, makes for the most fantastic heist movie to have never been made.

Monday, December 9th, 2019

It’s Time to Get Personal ◆ 24 ways

When people ask where to find you on the web, what do you tell them? Your personal website can be your home on the web. Or, if you don’t like to share your personal life in public, it can be more like your office. As with your home or your office, you can make it work for your own needs. Do you need a place that’s great for socialising, or somewhere to present your work? Without the constraints of somebody else’s platform, you get to choose what works for you.

A terrific piece from Laura enumerating the many ways that having your own website can empower you.

Have you already got your own website already? Fabulous! Is there anything you can do to make it easier for those who don’t have their own sites yet? Could you help a person move their site away from a big platform? Could you write a tutorial or script that provides guidance and reassurance?

Saturday, November 23rd, 2019

Save .ORG | SaveDotOrg.org

I’ve signed this letter.

Saturday, August 3rd, 2019

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

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

Tuesday, July 16th, 2019

Initial thoughts on standardizing form controls | Greg Whitworth

Greg has done a lot of research into developer frustrations with customising form controls.

My current thinking in this space, and I know some folks will find this controversial, but I think we should completely standardize in-page form controls with no limitations on their styling capabilities. What do I mean by in-page controls? I am referring to any form control or component that is rendered within the content process. This standardization would include the sub-parts and their related states and how these are exposed (probably through CSS psuedo classes or HTML attributes). This will enable the shadow-dom to be encapsulated while providing web developers with a consistent experience to adjust to match their brand and needs of their site/application.

Monday, July 1st, 2019

8 DOM features you didn’t know existed - LogRocket Blog

If you ignore the slightly insulting and condescending clickbaity title, this is a handy run-down of eight browser features with good support:

  1. extra arguments in addEventListener(),
  2. scrollTo(),
  3. extra arguments in setTimeout() and setInterval(),
  4. the defaultChecked property for checkboxes,
  5. normalize() and wholeText for strings of text,
  6. insertAdjacentElement() and insertAdjacentText(),
  7. event.detail, and
  8. scrollHeight and scrollWidth.

Tuesday, May 28th, 2019

W3C and WHATWG to work together to advance the open Web platform | W3C Blog

It’s Armistice Day in the world of HTML:

WHATWG maintains the HTML and DOM Living Standards.

W3C stops independent publishing of a designated list of specifications related to HTML and DOM and instead will work to take WHATWG Review Drafts to W3C Recommendations.

It feels like the loop is finally being closed on what I wrote about in the opening chapter of HTML5 For Web Designers back in 2010.

Thursday, May 2nd, 2019

The Web Developer’s Guide to DNS | RJ Zaworski

At Codebar the other night, I was doing an intro chat with some beginners. At one point I touched on DNS. This explanation is great for detailing what’s going on under the hood.

Friday, April 26th, 2019

How I failed the <a>

I think the situation that Remy outlines here is quite common (in client-rehydrated server-rendered pages), but what’s less common is Remy’s questioning and iteration.

So I now have a simple rule of thumb: if there’s an onClick, there’s got to be an anchor around the component.