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Detecting ActiveX plugins

The last thing to be aware of is that the

navigator.plugins

collection can sometimes become out of

date, or

stale

, as the user is downloading a plugin required for viewing your page. To prepare for this

possibility, you should always start out by refreshing

navigator.plugins

by calling the

refresh()

method. This method accepts one argument, a Boolean value, indicating whether the browser should

reload the page (or pages) using an embedded object; to reload the pages, pass in

true

, otherwise, pass

false

. For example:

navigator.plugins.refresh(true); //reload all pages using plugins

Making this simple call could save you some heartache later on.

Detecting ActiveX plugins

Because Internet Explorer plugins are just ActiveX controls, all you need to know is the name of the con-

trol to detect if it is installed. Earlier in this book, you saw some code to detect the latest version of the

Microsoft XML DOM. This same methodology can be used for any IE plugin. But how do you find the

name of the ActiveX control you’re interested in?

Microsoft has a tool called the OLE/COM Object Viewer that can be used to find the ActiveX control

name for all ActiveX controls installed on your computer. You can download this tool for free from

http://www.microsoft.com/downloads/details.aspx?FamilyID=5233b70d-d9b2-4cb5-

aeb6-45664be858b6&displaylang=en

. After it is installed, it provides a list of all OLE, COM, and

ActiveX objects installed on your machine as well as important information about each one. It may take

some time to look through all of the installed objects, but once you find the one you’re looking for, all the

pertinent information is displayed (Figure 18-1).

The important piece of information is listed as

VersionIndependentProgID

, which gives you the name

of the generic ActiveX control that creates the most recent version of the control. The

ProgID

listed typi-

cally gives you a version-specific control name, which helps to determine if a specific version is installed

(although it doesn’t always list the highest version available). The following table lists the version-

independent and version-specific ActiveX control names for several popular plugins.

Presently, Netscape Navigator 3.0+, Opera 5.0+, Safari 1.0, Internet Explorer 5.0+

(Macintosh only), Internet Explorer 3.0-5.5 SP 1 (Windows), and all Mozilla-based Web

browsers support this functionality; Internet Explorer 5.5 SP 2+ on Windows does not,

even though it creates both

navigator.plugins

and

navigator.mimeTypes

(each is

a collection with zero items).

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