HTML and CSS Reference
In-Depth Information
CHAPTER 9
Web Workers
When your web application requires heavy lifting or background processing on the
JavaScript side, the Web Workers API is your answer.
The Web Workers interface spawns real OS-level threads, allowing for data to be passed
back and forth between any given threads (or worker). Furthermore, because commuâ
nication points between threads are carefully controlled, concurrency problems are rare.
You cannot access components unsafe to threads or the DOM, and you have to pass
specific data in and out of a thread through serialized objects. So you have to work
extremely hard to cause problems in your code. Regardless of how you plan to use Web
Workers in your application, the main idea behind processing any behind-the-scenes
data lies in the idea of creating multiple workers (or threads) in the browser.
As of this writing, Safari, Safari for iOS5, Chrome, Opera, and Mozilla Firefox support
the Web Workers API, but Internet Explorer does not. (Internet Explorer 10 did add
support for Web Workers in Platform Preview 2.) Web Workers in Android versions 2.0
and 2.1 support Web Workers, as well, but later versions of Android do not. The only
shim currently available for Web Workers makes use of Google Gears. If the core Web
Workers API is not supported on a device or browser, you can detect if Google Gears is
installed. For more details, see
http://html5-shims.googlecode.com/svn/trunk/demo/work
ers.html
.
With Web Workers and its multithreaded approach, you do not have access to the DOM
(which is not thread safe), the
window
,
document
, or
parent
objects. You do, however,
have access to the quite a few other features and objects, starting with the
navigator
object:
appCodeName
//the code name of the browser
appName
//the name of the browser
