SoftLayer Blog » web development

Script Clip: HTML5 Audio Player with jQuery Controls

Cassandra Wolff — Thu, 07 Mar 2013 21:05:19 +0000

HTML5 and jQuery provide mind-blowing functionality. Projects that would have taken hours of development and hundreds of lines of code a few years ago can now be completed in about the time it’ll take you to read this paragraph. If you wanted to add your own audio player on a web page in the past, what would it have involved? Complicated elements? Flash (*shudders*)? It was so complicated that most developers just linked to the audio file, and the user just downloaded the file to play it locally. With HTML5, an embedded, cross-browser audio player can be added to a page with five lines of code, and if you want to get really fancy, you can easily use jQuery to add some custom controls.

If you’ve read any of my previous blogs, you know that I love when I find little code snippets that make life as a web developer easier. My go-to tools in that pursuit are HTML5 and jQuery, so when I came across this audio player, I knew I had to share. There are some great jQuery plugins to play music files on a web page, but they can be major overkill for a simple application if you have to include comprehensive controls and themes. Sometimes you just want something simple without all of that overhead:

Your browser does not support the audio element.

Oooh… Ahhh…

That song — Pop Bounce by SoftLayer’s very own Chris Interrante — is written in five simple lines of HTML5 code:

style="width:550px; margin: 0 auto; display:block;" controls>
  src="http://cdn.softlayer.com/innerlayer/Interrante-PopBounce.ogg" type="audio/ogg">
  src="http://cdn.softlayer.com/innerlayer/Interrante-PopBounce.mp3" type="audio/mpeg">
Your browser does not support the audio element.
</audio>

If IE 9+, Chrome 6+, Firefox 3.6+, Safari 5+ and Opera 10+ would all agree on supported file formats for the tag, the code snippet would be even smaller. I completely geek out over it every time I look at it and remember the days of yore. As you can see, the HTML5 application has some simple default controls: Play, Pause, Scan to Time, etc. As a developers, I couldn’t help but look for a to spice it up a little … What if we want to fire an event when the user plays, pauses, stops or takes any other action with the audio file? jQuery!

Make sure your jQuery include is in the of your page:

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script>

Now let’s use jQuery to script separate “Play” and “Pause” links … And let’s have those links fire off an alert when they are pressed:

$(document).ready(function(){
  $("#play-button").click(function(){
   $("#audioplayer")[0].play();
   alert('You have played the audio file!');
  })    
 
  $("#pause-button").click(function(){
   $("#audioplayer")[0].pause();
   alert('You have paused the audio file!');
  })    
})

With that script in the as well, the HTML on our page will look like this:

<div class=:"audioplayer">
  id="audioplayer" name="audioplayer" controls loop>
    src="http://cdn.softlayer.com/innerlayer/Interrante-PopBounce.ogg" type="audio/ogg">
    src="http://cdn.softlayer.com/innerlayer/Interrante-PopBounce.mp3" type="audio/mpeg">
  Your browser does not support the audio element.
  </audio>
 
  <a id="play-button" href="#">Play!</a>
  <a id="pause-button" href="#">Pause!</a>
</div>

Want proof that it works that simply? Boom.

You can theme it any way you like; you can add icons instead of the text … The world is your oyster. The bonus is that you’re using one of the lightest media players on the Internet! If you decide to get brave (or just more awesome), you can explore additional features. You’re using jQuery, so your possibilities are nearly limitless. If you want to implement a “Stop” feature (which returns the audio back to the beginning when “Stop” is pressed), you can get creative:

$("#stop-button").click(function(){
    $("#audioplayer")[0].currentTime = 0; // return the audio file back to the beginning
}

If you want to include some volume controls, those can be added in a snap as well:

$("#volumeUp").click(function(){
    $("#audioplayer")[0].volume +=0.1;
}
 
$("#volumeDown").click(function(){
    $("#audioplayer")[0].volume -=0.1;
}

Try it out and let me know what you think. Your homework is to come up with some unique audio player functionality and share it here!

-Cassandra

Web Development – JavaScript Packaging

Philip Thompson — Thu, 10 Jan 2013 20:15:05 +0000

If you think of JavaScript as the ugly duckling of programming languages, think again! It got a bad rap in the earlier days of the web because developers knew enough just to get by but didn’t really respect it like they did Java, PHP or .Net. Like other well-known and heavily used languages, JavaScript contains various data types (String, Boolean, Number, etc.), objects and functions, and it is even capable of inheritance. Unfortunately, that functionality is often overlooked, and many developers seem to implement it as an afterthought: “Oh, we need to add some neat jQuery effects over there? I’ll just throw some inline JavaScript here.” That kind of implementation perpetuates a stereotype that JavaScript code is unorganized and difficult to maintain, but it doesn’t have to be! I’m going to show you how easy it is to maintain and organize your code base by packaging your JavaScript classes into a single file to be included with your website.

There are a few things to cover before we jump into code:

JavaScript Framework – Mootools is my framework of choice, but you can use whatever JavaScript framework you’d like.
Classes – Because I see JavaScript as another programming language that I respect (and is capable of object-oriented-like design), I write classes for EVERYTHING. Don’t think of your JavaScript code as something you use once and throw away. Write your code to be generic enough to be reused wherever it’s placed. Object-oriented design is great for this! Mootools makes object-oriented design easy to do, so this point reinforces the point above.
Class Files – Just like you’d organize your PHP to contain one class per file, I do the exact same thing with JavaScript. Note: Each of the class files in the example below uses the class name appended with .js.
Namespacing – I will be organizing my classes in a way that will only add a single property — PT — to the global namespace. I won’t get into the details of namespacing in this blog because I’m sure you’re already thinking, “The code! The code! Get on with it!” You can namespace whatever is right for your situation.

For this example, our classes will be food-themed because … well … I enjoy food. Let’s get started by creating our base object:

/*
---
name: PT
description: The base class for all the custom classes
authors: [Philip Thompson]
provides: [PT]
...
*/
var PT = {};

We now have an empty object from which we’ll build all of our classes. We’ll go I will go into more details later about the comment section, but let’s build our first class: PT.Ham.

/*
---
name: PT.Ham
description: The ham class
authors: [Philip Thompson]
requires: [/PT]
provides: [PT.Ham]
...
*/
 
(function() {
    PT.Ham = new Class({
        // Custom code here...
    });
}());

As I mentioned in point three (above), PT.Ham should be saved in the file named PT.Ham.js. When we create second class, PT.Pineapple, we’ll store it in PT.Pineapple.js:

/*
---
name: PT.Pineapple
description: The pineapple class
authors: [Philip Thompson]
requires: [/PT]
provides: [PT.Pineapple]
...
*/
 
(function() {
    PT.Pineapple = new Class({
        // Custom code here...
    });
}());

Our final class for this example will be PT.Pizza (I’ll let you guess the name of the file where PT.Pizza lives). Our PT.Pizza class will require that PT, PT.Ham and PT.Pineapple be present.

/*
---
name: PT.Pizza
description: The pizza class
authors: [Philip Thompson]
requires: [/PT, /PT.Ham, /PT.Pineapple]
provides: [PT.Pizza]
...
*/
 
(function() {
    PT.Pizza = new Class({
        // Custom code here that uses PT.Ham and PT.Pineapple...
    });
}());

Before we go any further, let’s check out the comments we include above each of the classes. The comments are formatted for YAML — YAML Ain’t Markup Language (you gotta love recursive acronyms). These comments allow our parser to determine how our classes are related, and they help resolve dependencies. YAML’s pretty easy to learn and you only need to know a few basic features to use it. The YAML comments in this example are essential for our JavaScript package-manager — Packager. I won’t go into all the details about Packager, but simply mention a few commands that we’ll need to build our single JavaScript file.

In addition to the YAML comments in each of the class files, we also need to create a YAML file that will organize our code. This file — package.yml for this example — is used to load our separate JavaScript classes:

name: "PT"
description: "Provides our fancy PT classes"
authors: "[Philip Thompson]"
version: "1.0.0"
sources:
    - js/PT.js
    - js/PT.Ham.js
    - js/PT.Pineapple.js
    - js/PT.Pizza.js

package.yml shows that all of our PT* files are located in the js directory, one directory up from the package.yml file. Some of the properties in the YAML file are optional, and you can add much more detail if you’d like, but this will get the job done for our purposes.

Now we’re ready to turn back to Packager to build our packaged file. Packager includes an option to use PHP, but we’re just going to do it command-line. First, we need to register the new package (package.yml) we created for PT. If our JavaScript files are located in /path/to/web/directory/js, the package.yml file is in /path/to/web/directory:

./packager register /path/to/web/directory

This finds our package.yml file and registers our PT package. Now that we have our package registered, we can build it:

./packager build * > /path/to/web/directory/js/PT.all.js

The Packager sees that our PT package is registered, so it looks at each of the individual class files to build a single large file. In the comments of each of the class files, it determines if there are dependencies and warns you if any are not found.

It might seem like a lot of work when it’s written out like this, but I can assure you that when you go through the process, it takes no time at all. The huge benefit of packaging our JavaScript is evident as soon as you start incorporating those JavaScript classes into your website … Because we have built all of our class files into a single file, we don’t need to include each of the individual JavaScript files into our website (much less include the inline JavaScript declarations that make you cringe). To streamline your implementation even further if you’re using your JavaScript package in a production deployment, I recommend that you “minify” your code as well.

See … Organized code is no longer just for server-side only languages. Treat your JavaScript kindly, and it will be your friend!

Happy coding!

-Philip

Tips and Tricks – Pure CSS Sticky Footers

Cassandra Wolff — Tue, 06 Nov 2012 20:00:17 +0000

By now, if you’ve seen my other blog posts, you know that I’m fascinated with how much JavaScript has evolved and how much you can do with jQuery these days. I’m an advocate of working smarter, not harder, and that maxim knows no coding language limits. In this post, I want to share a pure CSS solution that allows for “sticky” footers on a web page. In comparing several different techniques to present this functionality, I found that all of the other routes were overkill when it came to processing time and resource usage.

Our objective is simple: Make the footer of our web page stay at the bottom even if the page’s content area is shorter than the user’s browser window.

This, by far, is one of my *favorite* things to do. It makes the web layout so much more appealing and creates a very professional feel. I ended up kicking myself the very first time I tried to add this functionality to a project early in my career (ten years ago … already!?) when I found out just how easy it was. I take solace in knowing that I’m not alone, though … A quick search for “footer stick bottom” still yields quite a few results from fellow developers who are wrestling with the same frustrating experience I did. If you’re in that boat, fear no more! We’re going to your footers in shape in a snap.

Here’s a diagram of the problem:

Unfortunately, a lot of people try to handle it with setting a fixed height to the content which would push the footer down. This may work when YOU view it, but there are several different browser window heights, resolutions and variables that make this an *extremely* unreliable solution (notice the emphasis on the word “extremely” … this basically means “don’t do it”).

We need a dynamic solution that is able to adapt on the fly to the height of a user’s browser window regardless if the resize it, have Firebug open, use a unique resolution or just have a really, really weird browser!

Let’s take a look at what the end results should look like:

To make this happen, let’s get our HTML structure in place first:

<div id="page">
 
      <div id="header"> </div>
 
      <div id="main"> </div>
 
      <div id="footer"> </div>
 
</div>

It’s pretty simple so far … Just a skeleton of a web page. The page div contains ALL elements and is immediately below the tags in the page code hierarchy. The header div is going to be our top content, the main div will include all of our content, and the footer div is all of our copyrights and footer links.

Let’s start by coding the CSS for the full page:

Html, body {
      Padding: 0;
      Margin: 0;
      Height: 100%;
}

Adding a 100% height allows us to set the height of the main div later. The height of a div can only be as tall as the parent element encasing it. Now let’s see how the rest of our ids are styled:

#page {
      Min-height: 100%;
      position:relative;
}
 
#main {
      Padding-bottom: 75px;   /* This value is the height of your footer */
}
 
#footer {
      Position: absolute;
      Width: 100%;
      Bottom: 0;
      Height: 75px;  /* This value is the height of your footer */
}

These rules position the footer “absolutely” at the bottom of the page, and because we set #page to min-height: 100%, it ensures that #main is exactly the height of the browser’s viewing space. One of the best things about this little trick is that it’s compliant with all major current browsers — including Firefox, Chrome, Safari *AND* Internet Explorer (after a little tweak). For Internet Explorer to not throw a fit, we need concede that IE doesn’t recognize min-height as a valid property, so we have to add Height: 100%; to #page:

#page {
      Min-height: 100%;  /* for all other browsers */
      height: 100%;  /* for IE */
      position:relative;
}

If the user does not have a modern, popular browser, it’s still okay! Though their old browser won’t detect the magic we’ve done here, it’ll fail gracefully, and the footer will be positioned directly under the content, as it would have been without our little CSS trick.

I can’t finish this blog without mentioning my FAVORITE perk of this trick: Should you not have a specially designed mobile version of your site, this trick even works on smart phones!

-Cassandra

Tips and Tricks – jQuery Lazy Load Plugin

Cassandra Wolff — Wed, 26 Sep 2012 14:00:25 +0000

In the late 90′s, web pages presented their information in a relatively structured fashion, with little concern on how “pretty” the content looked. To a certain extent, that was a result of available technology and resources being a little more limited, but much of the reason was probably because we had no idea what was possible. We’ve come a long way, my friend. These days, it’s tough to spend an hour online without coming across a gorgeous web site with huge animations, a pallet of every color possible, full-width backgrounds and high definition detail.

Those sites may be aesthetically pleasing, but they can be a big pain from a developer’s perspective.

How much load does all of that stuff put on the server every time that web page is visited? As developers, it’s our job to think about both what the visitor sees AND the visitor’s experience in seeing it. Even the most beautiful sites will be ignored if a page takes too long to load. We spend hours optimizing every detail so users can fluidly browse without having to wait. It was in one of these optimization sessions that I discovered “lazy load.”

To be honest, I wasn’t too fond of the word “lazy” in the name, and I especially wasn’t fond of having to explain to my boss that *I* wasn’t being lazy … The jQuery plugin is *named* “Lazy Load.” Lazy Load effectively allows large pieces of content to stay in the backlog until they’re needed. To give you an example of what that looks like, let’s say you have a website with three humungous images, but they’re all in different locations. Instead of pushing the entire load onto the user when they first land on your page, we can break them up and have them load only when the user goes to view them. We’re not reducing the size of the web page; we’re merely helping it work smarter.

Without Lazy Load, a normal web page loads each item when its page is visited. If a website has videos, music, images and some neat user interactivity applications, each of those items will load at the same time:

If you take into consideration how large each of those items are, you can sense the problem. The user only has so much bandwidth to load these items, and something’s gotta give. Usually, it means long loading times. We can’t control how fast each user’s ISP is, but we can reorder our items and let Lazy Load help us prioritize items and load the page more efficiently.

After we snag Lazy Load on Github (jquery.lazyload.js), we put our jQuery scripts in the of our page:

<script src="jquery.js" type="text/javascript">script> 
<script src="jquery.lazyload.js" type="text/javascript">script>

Now that the plugin is available to us, we need to determine what we want to load lazily. Images are probably one of the most bothersome page elements, so let’s apply Lazy Load to the images we load in the belazy class. In the of your page (or in the footer if you prefer your JavaScript entries there), you’ll add:

<script type="text/javascript">$("img.belazy").lazyload();script>

As a result of that function, all image tags with a class of belazy will have Lazy Load run on them. This helps us ensure that we’re not loading ALL of our images lazily. Now we need to choose which images we want to apply Lazy Load to.

Let’s say the image tag of the largest image on one of our page looks like this:

<img src="bighonkingimage.png"/>

To have the lazyload function apply to it, we just have to make a couple tweaks:

<img class="belazy" src="bighonkingimage.png" data-original="bighonkingimage.png"/>

We added class="belazy" to trigger the lazyload function, and we added data-original="bighonkingimage.png" to line up with the formatting required by the newest version of Lazy Load (it’s simply a repeat of the source).

When a user visits our page, bighonkingimage.png will load only when it’s needed!

Pretty neat, eh?

-Cassandra

Web Development – JavaScript – Creating a Sticky Menu

Philip Thompson — Wed, 23 May 2012 15:50:10 +0000

When designing websites, I like to focus on ease of use and accessibility for the end user. While creating your site to be friendly to screen readers and text-based browsers is a must, the accessibility I’m referring to is making it easy for your audience to navigate your site and perform certain common actions. By providing an easy interface for your users, you are immediately increasing your chances that they’ll return for more of your site’s goodness.

Thus far in our “Web Development” blog series, we’ve looked at JavaScript Optimization, HTML5 Custom Data Attributes, HTML5 Web Fonts and using CSS to style the Highlight Selection. In this post, we’re going to create a “sticky” menu at the top of a page. As a user scrolls down, the menu will “stick” to the top and always be visible (think of Facebook’s Timeline view), allowing the user quicker access to clicking common links. With some simple HTML, CSS and JavaScript, you can have a sticky menu in no time.

Let’s start with our HTML. We’re going to have a simple header, menu and content section that we’ll throw in our tag.

<header>
    <h1>My Headerh1>
header>
<nav id="menu">
    <ul id="menu-list">
        <li>Itemsli>
    ul>
nav>
<div id="content">
    Some content
div>

For brevity, I’ve shortened the content I show here, but the working example will have all the information. Now we can throw in some CSS to style our elements. The important part here is how the

is styled.

nav#menu {
    background: #FFF;
    clear: both;
    margin: 40px 0 80px 0;
    width: 99.8%;
    z-index: 2;
}
ul#menu-list li {
    border: solid 1px blue;
    list-style-type: none;
    display: inline-block;
    margin: 0 -3px;
    padding: 4px 10px;
    width: auto;
}

We have set the menu’s background to white (#FFF) and given it a z-index of 2 so that when the user scrolls, the menu will stay on top and not be see-through. We’ve also set the list items to be styled inline-block, but you can style your items however you desire.

Now we get to the fun part – the JavaScript. I’ve created a class using Mootools, but similar functionality could be achieved using your favorite JavaScript framework. Let’s examine our initialize method (our constructor) in our Stickit class.

var Stickit = this.Stickit = new Class({
    initialize: function(item, options) {
        // 'item' is our nav#menu in this case
        this.item = document.id(item);
 
        // The element we're scrolling will be the window
        this.scrollTarget = document.id(options.scrollTarget || document.window);
 
        // The 'anchor' is an empty element that will always keep the same location
        // when the user scrolls. This is needed because this.item will change and
        // we cannot rely on it for accurate calculations.
        this.anchor = new Element('div').inject(this.item, 'top');
 
        // The 'filler' is an empty element that we'll use as a space filler for when
        // the 'item' is being manipulated - this will prevent the content below from
        // jumping around when we scroll.
        this.filler = new Element('div').inject(this.item, 'after');
 
        // Set the styles of our 'filler' to match the styles of the 'item'
        this.setFillerStyles();
 
        // Initialize our scroll events – see the next code section for details
        this.initEvents();
    }
});

What we’re doing here is grabbing our element to stick to the top – in this case, nav#menu – and initializing our other important elements. I’ll review these in the next code section.

var Stickit = this.Stickit = new Class({
    ...
    initEvents: function() {
        var that = this,
            // Grab the position of the anchor to be used for comparison during vertical scroll
            anchorOffsetY = this.anchor.getPosition().y,
            // Grab our original styles of our 'item' so that we can reset them later
            originalStyles = this.item.getStyles('margin-top', 'position', 'top');
 
        // This is the function we'll provide as our scroll event handler
        var stickit = function(e) {
            // Determine if we have scrolled beyond our threshold - in this case, our
            // anchor which is located as the first element of our 'item'
            var targetScrollY = that.scrollTarget.getScroll().y,
                fixit = targetScrollY > anchorOffsetY;
 
            if (fixit && that.cache != 'fixed') {
                // If we have scrolled beyond the threshold, fix the 'item' to the top
                // of the window with the following styles: margin-top, position and top
                that.item.setStyles({
                    'margin-top': 0,
                    position: 'fixed',
                    top: 0
                });
                // Show our (empty) filler so that the content below the 'item' does not
                // jump - this would otherwise be distracting to the user
                that.filler.setStyle('display', 'block');
                // Cache our value so that we only set the styles when we need to
                that.cache = 'fixed';
            }
            else if (!fixit && that.cache != 'default') {
                // We have not scrolled beyond the threshold.
                // Hide our filler
                that.filler.setStyle('display', 'none');
                // Reset the styles to our 'item'
                that.item.setStyles(originalStyles);
                // Cache our values so we don't keep resetting the styles
                that.cache = 'default';
            }
        };
 
        // Add our scroll event to the target - the 'window' in this case
        this.scrollTarget.addEvent('scroll', stickit);
        // Fire our scroll event so that all the elements and styles are initialized
        this.scrollTarget.fireEvent('scroll');
    }
});

This method contains the meat of our functionality. The logic includes that we test how far the user has scrolled down on the page. If s/he scrolls past the threshold – in this case, the anchor which is located at the very top of the “stuck” item – then we set the menu to be fixed to the top of the page by setting the CSS values for margin-top, position and top. We also display a filler so that the content below the menu doesn’t jump when we set the menu’s position to fixed. When the user scrolls back to the top, the styles are reset to their original values and the filler is hidden.

To see a full working example, check out this fiddle. The Stickit class I created is flexible enough so that you can “stick” any element to the top of the page, and you can specify a different scrollTarget, which will allow you to scroll another element (besides the window) and allow the item to stick to the top of that element instead of the window. If you want to give that a try, you can specify different options in Stickit and modify your CSS as needed to get it working as you’d like.

Happy coding,

-Philip

Web Development – CSS – Highlight Selection

Philip Thompson — Tue, 13 Mar 2012 21:07:08 +0000

I immediately fell in love with CSS when we were introduced in late 2000. The ability to style a whole site outside the HTML was a fantastic concept and probably my first true introduction to separation of style and content. Put your words over here, and put how you display those words over there. So simple! Since then I have always been an advocate of cascading style sheets. Today’s tip will involve an effortless addition that will have your readers say, “Ooooh. That’s a clever little change.”

I find that when I read articles and blogs online, I not only read with my eyes, I scan the page with my mouse. Especially if it’s a wordy article or not styled in smaller columns, I highlight the text by clicking and dragging to help me maintain my focus. Up until recently, whenever you selected text that way in your browser, your operating system would choose the color of the background highlight. For Windows, this is generally blue. For OS X, this is whatever you’ve set your preferences to (which is light blue by default).

For those of you that use a newer version of Webkit (Chrome or Safari) or Gecko (Firefox), the site designer can determine what color to highlight your selection of text, and CSS has made it easy.

/* Webkit */
::selection {
    background: #972F2C;
    color: #FFF;
}
/* Gecko/Mozilla */
::-moz-selection {
    background: #972F2C;
    color: #FFF;
}

As of today, Webkit browsers are the only ones that support ::selection without browser prefixing. Firefox requires the -moz- prefix. Here we have set the highlight background color to “SoftLayer Red” (#972F2C) and made the text color white (#FFF). It should be noted that earlier versions of Webkit and Gecko did not support anything but the background property. There is still limited support for which CSS properties are allowed during selection. You are unable to change font-style, font-size, text-decoration and many other properties, but we can hope support for most of the properties will be available in the future.

This is pretty cool so far, but we can take it one small step further. Just like other selectors, we can apply the ::selection selector to other elements and style each one differently.

h2::selection {
    background: #B72E33;
    color: #FFF;
}
p::selection {
    background: #ACEFB2;
}
div::selection {
    background: #E4DB80;
}
span::selection {
    background: #C780E4;
    color: #FFF;
}

This produces the following:

Surprise your readers and give them some highlight goodness.

Happy coding!

-Philip

Web Development – HTML5 – Custom Data Attributes

Philip Thompson — Tue, 10 Jan 2012 17:30:29 +0000

I recently worked on a project that involved creating promotion codes for our clients. I wanted to make this tool as simple as possible to use and because this involved dealing with thousands of our products in dozens of categories with custom pricing for each of these products, I had to find a generic way to deal with client-side form validation. I didn’t want to write custom JavaScript functions for each of the required inputs, so I decided to use custom data attributes.

Last month, we started a series focusing on web development tips and tricks with a post about JavaScript optimization. In this installment, we’re cover how to use HTML5 custom data attributes to assist you in validating forms.

Custom data attributes for elements are “[attributes] in no namespace whose name starts with the string ‘data-’, has at least one character after the hyphen, is XML-compatible, and contains no characters in the range U+0041 to U+005A (LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z).” Thanks W3C. That definition is bookish, so let’s break it down and look at some examples.

Valid:

<div data-name="Philip">Mr. Thompson is an okay guy.div>
<a href="softlayer.com" data-company-name="SoftLayer" data-company-state="TX">SoftLayera>
<li data-color="blue">Smurfsli>

Invalid:

// This attribute is not prefixed with 'data-'
    <h2 database-id="244">Foodh2>
 
// These 2 attributes contain capital letters in the attribute names
    <p data-firstName="Ashley" data-lastName="Thompson">...p>
 
// This attribute does not have any valid characters following 'data-'
    <img src="/images/pizza.png" data-="Sausage" />

Now that you know what custom data attributes are, why would we use them? Custom attributes allow us to relate specific information to particular elements. This information is hidden to the end user, so we don’t have to worry about the data cluttering screen space and we don’t have to create separate hidden elements whose purpose is to hold custom data (which is just bad practice). This data can be used by a JavaScript programmer to many different ends. Among the most common use cases are to manipulate elements, provide custom styles (using CSS) and perform form validation. In this post, we’ll focus on form validation.

Let’s start out with a simple form with two radio inputs. Since I like food, our labels will be food items!

<input type="radio" name="food" value="pizza" data-sl-required="food" data-sl-show=".pizza" /> Pizza
<input type="radio" name="food" value="sandwich" data-sl-required="food" data-sl-show="#sandwich" /> Sandwich
<div class="hidden required" data-sl-error-food="1">A food item must be selecteddiv>

Here we have two standard radio inputs with some custom data attributes and a hidden div (using CSS) that contains our error message. The first input has a name of food and a value of pizza – these will be used on the server side once our form is submitted. There are two custom data attributes for this input: data-sl-required and data-sl-show. I am defining the data attribute data-sl-required to indicate that this radio button is required in the form and one of them must be selected to pass validation. Note that I have prefixed required with sl- to namespace my data attribute. required is generic and I don’t want to have any conflicts with any other attributes – especially ones written for other projects! The value of data-sl-required is food, which I have tied to the div with the attribute data-sl-error-food (more on this later).

The second custom attribute is data-sl-show with a selector of .pizza. (To review selectors, jump back to the JavaScript optimization post.) This data attribute will be used to show a hidden div that contains the class pizza when the radio button is clicked. The sandwich radio input has the same data attributes but with slightly different values.

Now we can move on to our HTML with the hidden text inputs:

<div class="hidden pizza">
    Pizza type: <input type="text" name="pizza" data-sl-required="pizza" data-sl-depends="{"type":"radio","name":"food","value":"sandwich"}" />
    <div class="hidden required" data-sl-error-pizza="1">The pizza type must not be emptydiv>
div>
 
<div class="hidden" id="sandwich">
    Sandwich: <input type="text" name="sandwich" data-sl-required="sandwich" data-sl-depends="{"type":"radio","name":"food","value":"sandwich"}" />
    <div class="hidden required" data-sl-error-sandwich="1">The sandwich must not be emptydiv>
div>

These are hidden divs that contain text inputs that will be used to input more data depending on the radio input selected. Notice that the first outer div has a class of pizza and the second outer div has an id of sandwich. These values tie back to the data-sl-show selectors for the radio inputs. These text inputs also contain the data-sl-required attribute like the previous radio inputs. The data-sl-depends data attribute is a fun attribute that contains a JSON-encoded object that’s been run through PHP’s htmlentities() function. For readability, the data-sl-depends values contain:

{"type":"radio","name":"food","value":"pizza"}
{"type":"radio","name":"food","value":"sandwich"}

This first attribute says that our text input “depends” on the radio input with the name food and value pizza to be visible and selected in order to be processed as required. You can just imagine the possibilities of combinations you can create to make very custom functionality with very generic JavaScript.

Now we can examine our JavaScript to make sense of all these custom data attributes. Note that I’ll be using Mootools’ syntax, but the same can fairly easily be accomplished using jQuery or your favorite JavaScript framework. I’m going to start by creating a DataForm class. This will be generic enough so that you can use it in multiple forms and it’s not tied to this specific instance. Reuse is good! To have it fit our needs, we’re going to pass some options when instantiating it.

new DataForm({
    ...,
    dataAttributes: {
        required: 'data-sl-required',
        errorPrefix: 'data-sl-error',
        depends: 'data-sl-depends',
        show: 'data-sl-show'
    }
});

As you can see, I’m using the data attribute names from our form as the options – this will allow you to create your own data attribute names depending on your uses. We first need to make our hidden divs visible whenever our radio buttons are clicked – we’ll use our initData() method for that.

initData: function() {
    var attrs = this.options.dataAttributes,
        divs = [];
 
    $$('input[type=radio]['+attrs.show+']').each(function(input) {
        var div = $$(input.get(attrs.show));
        divs.push(div);
        input.addEvent('change', function(e) {
            divs.each(function(div) { div.hide(); });
            div.show();
        });
    });
}

This method grabs all the radio inputs with the show attribute (data-sl-show) and adds an onchange event to each of them. When a radio input is checked, it first hides all the divs, and then shows the div that’s associated with that radio input.

Great! Now we have our text inputs showing and hiding depending on which radio button is selected. Now onto the actual validation. First, we’ll make sure our required radio inputs are checked:

$$('input[type=radio]['+attrs.required+']:not(:checked)').each(function(input) {
    var name = input.get('name');
    checkError(name, isRadioWithNameSelected(name))
});

This grabs all the unchecked radio inputs with the required attribute (data-sl-required) and checks to see if any radio with that same name is selected using the function isRadioWithNameSelected(). The checkError() function will show or hide the error div (data-sl-error-*) depending if the radio is checked or not. Don’t worry – you’ll see how these functions are implemented in the JSFiddle below.

Now we can check our text inputs:

$$('input[type=text]['+attrs.required+']:visible').each(function(input) {
    var name = input.get('name'),
        depends = input.get(attrs.depends),
        value = input.get('value').trim();
 
    if (depends) {
        depends = JSON.encode(depends);
        switch (depends.type) {
            case 'radio':
                if (depends.name && depends.value) {
                    var radio = $$('input[type=radio][name="'+depends.name+'"][value="'+depends.value+'"]:checked');
                    if (!radio) {
                        checkError(input.get(attrs.required), true);
                        return;
                    }
                }
                break;
        }
    }
 
    checkError(name, value!='');
});

This obtains the required and visible text inputs and determines if they are empty or not. Here we look at our depends object to grab the associated radio inputs. If that radio is checked and the text input is empty, the error message appears. If that radio is not checked, it doesn’t even evaluate that text input. The depends.type is in a switch statement to allow for easy expansion of types. There are other cases for evaluating relationships … I’ll let you come up with more for yourself.

That concludes our usage of custom data attributes in form validation. This really only touched upon the very tip of the iceberg. Data attributes allow you – the creative developer – to interact in a new, HTML-valid way with your web pages.

Check out the working example of the above code at jsfiddle.net. To read more on custom data attributes, see what Google has to say. If you want to see really cool functionality that uses data attributes plus so much more, check out Aaron Newton’s Behavior module over at clientcide.com.

Happy coding!

-Philip