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Detecting Plugins

As with most Web technology, two types of plugins are available: those from Microsoft and those from

others. The Microsoft way uses ActiveX technology, which you may remember as the way to create

XML-related objects; the other way has been called

Netscape-style plugins

because Netscape Navigator

introduced the concept of plugins to the Web. Until recently, Internet Explorer supported Netscape-style

plugins in addition to ActiveX controls. Beginning with Internet Explorer 5.5 Service Pack 2 (Windows

only), however, Microsoft eliminated support for the Netscape-style plugins.

The main difference between the two types of plugins is the architecture. ActiveX plugins are built on

Microsoft’s ActiveX platform whereas Netscape-style plugins are built on top of the Netscape Plugin

API. Originally, every browser (including Internet Explorer) was forced to support the Netscape-style

plugins because Netscape was the dominant browser and only compatible browsers could compete.

Although many will speculate why Microsoft ended support for Netscape-style plugins, it has created

a clear rift in the world of plugins. Many plugin developers are required to create both Netscape-style

plugins and ActiveX wrappers for these plugins in order to support Internet Explorer.

Today, browsers are separated into those that don’t support Netscape-style plugins (such as Internet

Explorer on Windows) and those that do (such as Mozilla, Opera, Safari, and many other browsers).

Because of these differences, you have different ways of detecting whether a plugin is installed on a

given browser.

Detecting Netscape-style plugins

Since Netscape 3.0, many browsers (notably those based on Mozilla) allow JavaScript to determine

which MIME types are mapped to plugins, ultimately enabling you to determine if a given plugin is

installed. This is determined through the help of the

window.mimeTypes

collection.

Two types of Netscape-style plugins exist: the style used in Netscape 4.x and the newer Gecko style used

in Mozilla. The details of the differences are of no consequence to JavaScript developers because both

styles are accessed the same way.

Each MIME type registered to a plugin is present in

window.mimeTypes

, indexed both by number and

by MIME type, allowing you to access a MIME type directly or to iterate through the collection. An

object with four properties represents each MIME type:

description

— A description of the type of file represented by the MIME type

enabledPlugin

— Reference to a plugin object with information about the specific plugin

suffixes

— The file suffixes associated with this MIME type (such as mapping

.gif

image/gif

)

type

— The MIME type

You can print out a list of all visible MIME types and their descriptions by running a simple script:

<html>

<head>

<title>MIME Types Example</title>

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Interacting with Plugins

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