HTML5与未来的网页设计（英文教程）(2)

Extending the API

The most obvious benefit built into HTML5 is the numerous APIs and the opportunities it opens up for the future of web apps with Holy Grail of application cache and offline capabilities. Google Gears gave us offline data storage and Flash introduced us to the power of application cache (Pandora uses it to save your log in information). With HTML5, these capabilities are now available to use right in the language and can easily be expanded with JavaScript.

HTML5 relies on light scripting to flex its muscles on the Web; this is very possibly the first time, other than jQuery, that one (front-end) technology has fully acknowledged another. Sure, we connect them with classes and IDs but up until now, they have been perceived as separate layers by the principles of progressive enhancement. But as the Web grows we need unity like this across the Web.

Offline Data Storage

The coolest part about HTML5 is definitely its offline capabilities. Programs like Thunderbird and Outlook (and now GMail to an extent) let you browse through your old data while staying offline. With HTML5, you’ll have this same functionality, but in the browser. This is the first serious step towards bridging the gap between the desktop and the Web, and opens all sorts of doors for the future of Web apps.

The W3C has taken the best parts from the various Web technologies and rolled them into, what is being dubbed the most powerful markup language to date.

Some other of the HTML5 APIs

• Drag & Drop
  The drag and drop API defines an event-based drag and drop system. However, it never defines what “drag and drop” is. This API requires JavaScript to fully work as normal think drag and drop functionality.
• Video & Audio
  The audio & video APIs are massive upgrades in media embedding. Although support is limited right now, something like video embedding has never been easier:

   

  <video width="400" height="360" src="vid.mp4">

• Geolocation
  Geolocation is a very cool API available within HTML5. Its object can be used to programmatically determine location information through a device’s user agent (hint hint: mobile devices).

Further reading on the HTML5 API

• Offline Web Applications
• Offline Application Caching
• Remy Sharp on JavaScript APIs HTML5 (presentation)
• O3D Beach Demo from Google (must have an HTML5 capable browser)

Where can I use it?

Even with the very limited support for HTML5, the Web is far too progressive to not create a testing environment for us to play around. Currently, Safari is our best testing platform, as it supports most of the new elements and APIs. Of course, that may change at anytime so keep and eye on Opera, Chrome and Firefox as well.

Normally you might think since Safari is a Webkit browser, by default, all Webkit browsers would support the same elements, unfortunately, this isn’t the case. While many of the HTML5 features are supported across the board in Webkit browsers, there are some, like <video>, that are not.

Mobile devices

To effectively use HTML5 right now, we need to be able to control the environment in which it is used. Since support is not as widespread as we’d like it doesn’t make real sense for it to be heavily used unless, of course, we can lock down the usage to certain platforms which have HTML5 support. With Webkit leading the way for HTML5, we can safely focus on devices powered by Webkit.

The 3 hottest mobile devices right now: The Palm Pre, iPhone 3Gs and the new Google Android phone all have browsers that are based off the Webkit rendering engine.

Safari is even leading the way on the mobile HTML5 front; The iPhone (with the latest software upgrade) is the only device I could get to properly render the <audio> element. Because these devices are so young and all use the same rendering engine, the likelihood of them pushing a rapid software upgrade is pretty high.

Right now, you can confidently use many of the HTML5 features in iPhone Web app development and mostly likely expect Pre and Android to follow in suit.

Further reading on where you can use HTML5

• HTML5 Features in latest iPhone
• GMail Web app for the iPhone
• GMail for HTML5
• Supported Features in HTML5
• HTML5 Cheat Sheet

How can we move forward?

Even with all the recent hype surrounding HTML5 and how we all want to use it, it is still going to be a very slow transition away from HTML4.01 & XHTML1.0. It will take time to get developers up to speed, test all the features, waiting for all the :ahem: browsers to catch up, and it will take an especially long time for users to transition out of those old browsers. With all that in mind, we know who we are, we’re all reading this article (I’ve read it about 30 times so far) and we know we have to find a legitimate way to move forward without damaging the past.

We can’t make the full switch yet and there’s no use at this point pointing out who is holding up the show. We all know that any responsible developer would not drop support for a browser that is still heavily used. So rather than yell at a brick wall, here are some things I’ve found that might help us move forward in a positive way:

Semantic DIV naming

Semantically aligning your DIV names with that of the new HTML5 elements will help you get used to the names themselves and also the new functionality and nesting that they want you to do with the <header> and <footer> elements. These are akin to learning the intro the Enter Sandman (for the guitarist out there); it’s not very difficult, but it takes a little practice to get it to feel natural.

Before jumping in full-force to HTML5 production sites, I recommend trying the soft transition with changing your DIV names slightly. There’s no downside that I’ve found to doing this, you can even use the new DOCTYPE with very little consequence.

Faking it with JavaScript

First off, I’d like to say: Please don’t do this in production. If the client side scripting fails, it will completely collapse the site in browsers that won’t take CSS applied to the new elements. This is simply not a good option. It is, however, an option and I’m all about knowing your options no matter what they are.

Creating the new elements with JavaScript

Working in jQuery is cool and all, but as it turns out, there is a built in function to JavaScript to deal with creating new elements:

document.createElement('header');
document.createElement('footer');
document.createElement('section');
document.createElement('aside');
document.createElement('nav');
document.createElement('article');
document.createElement('figure');
document.createElement('time');

…and so on in that fashion.

This will allow you to style these elements in Internet Explorer. Again, the downside of using this technique is that, without the all-important JavaScript, the site will not only be unstyled, all the unrecognized elements will default to inline. So your site will literally collapse on itself.

Client side JavaScript is not the answer for using HTML5. Server side javascript, now that’s a completely different story…