New IE 10 Developer Preview (with Windows 8 Consumer Preview)

John Jainschigg (March 16, 2012)

As recently noted, the big news in computing and Internet last week was GA on Windows 8 Consumer Preview, a mostly functional, mostly sanded-smooth pre-release of Windows 8, largely meant for developer and serious early-adopter delectation. With that release comes the newest developer rev (#5, following the #4 rev of last November) of Internet Explorer 10, which uses the same HTML rendering engine as the OS. For the time being, the two are bound together: you have to install Windows 8 CP to get the newest IE 10, and (for the normally cautious) that requires a spare PC, or at least a partition on a non-mission-critical lab box. Ultimately, of course, IE10 will be available for all current versions of desktop and server Windows, e.g. Windows 7, Windows Server 2008 R2, etc.

The biggest overt change in IE10 from last year's developer pre-release is that the browser can now work both in a conventional, plug-in-enabled desktop mode, and under the much-acclaimed Metro user interface convention set, which is primarily for touch-enabled mobiles. Initial response to IE in Metro is coming from a small group of well-placed devs and other interested parties who – on the face of it – can dedicate a touchscreen PC (or partition on same) to the Windows 8 CP install. The tone of initial comments from objective sources like Gizmodo has been uniformly positive, praising the fluency of navigation, zooming and panning via swipes, double-taps and pinches, and the emergence of new parking and minimization modes, such as the so-called ‘snap mode,' where the browser snaps side-by-side with another Metro application.

As IE10 nears completion, the list of ‘arguably core' HTML5 and CSS3 new-feature additions is growing shorter, but some significant improvements to core features are still being made. There are so many of these improvements that it's worth visiting Microsoft's IEblog (see http://blogs.msdn.com/b/ie/archive/2012/03/02/web-platform-features-in-windows-consumer-preview.aspx ) for the complete list.

While many of the new/improved features will be of primary interest to deep HTML5 application developers (e.g. the first full availability of the long-awaited CORS [Cross-Origin Resource Sharing] XMLHttpRequest facility for secure cross-domain AJAX), there's plenty of good candy here for front-ends-mostly/only folks. One example is that IE10 now offers a full implementation of the HTML5 async and defer conventions for script loading control and status inquiry. In the simplest case, adding the async flag to a <script> element with a src parameter tells the browser that no dependencies exist between loading/rendering and inline script execution, so it can sort things out for maximum load speed and efficiency. The defer="true" attribute performs the complementary function of deterministically requesting that object execution be delayed until after the page is parsed and objects are accessible via the DOM in final dynamic forms. You can access the status of these flags on an object-by-object basis via JavaScript as well.

Routine use of these HTML5 features should have several good effects. In many cases – as when JavaScript-based UI functionality is provided but a page is designed to fall back gracefully and function where JavaScript has been disabled – such pages will load and be useful much faster. At a slightly more philosophically profound level, by making it possible to safely produce maintainable "JavaScript at the top" pages while maintaining close control of inline execution vs. the DOM, these features encourage healthy engineering practice and hewing to web standards.

John Jainschigg is a contributing editor for Slashdot and SourceForge.