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The Platform/Operating SystemDetection Script

Adding these checks to the code, you get the following:

var isNS4 = !isIE && !isOpera && !isMoz && !isKHTML

&& (sUserAgent.indexOf(“Mozilla”) == 0)

&& (navigator.appName == “Netscape”)

&& (fAppVersion >= 4.0 && fAppVersion < 5.0);

This variable accurately determines if the browser is Netscape Communicator. Next you want to deter-

mine the minimal versions. For this, you should check for version 4.0, 4.5 (which was a major release

with lots of code improvements), 4.7 (another major release), and 4.8 (the last release).

var isMinNS4 = isMinNS4_5 = isMinNS4_7 = isMinNS4_8 = false;

And because Netscape Communicator stores its version number in a logical way, it is very easy to deter-

mine the values for these variables:

if (isNS4) {

isMinNS4 = true;

isMinNS4_5 = fAppVersion >= 4.5;

isMinNS4_7 = fAppVersion >= 4.7;

isMinNS4_8 = fAppVersion >= 4.8;

}

The first variable,

isMinNS4

, is automatically set to

true

because this was one of the tests performed

when calculating

isNS4

. All the other minimal versions must be checked for in the normal way.

This completes the browser detection portion of the script. Next up is platform and operating system

detection.

The Platform/Operating System

Detection Script

Now that you have delved into the world of browser detection at great length, you must meet another

challenge: figuring out the operating system on the client’s machine. Even though the browser compa-

nies say that their browsers act the same across different platforms and operating systems, it is not so.

Take the case of Internet Explorer. On Windows, a powerful interface allows Microsoft ActiveX controls

to be embedded in pages or used in JavaScript. The problem is that these ActiveX controls require

Windows to work. So even though Microsoft says that IE on Unix and Macintosh works the same as IE

on Windows, you know that this is impossible. Therefore, you must, at least, be able to tell which operat-

ing system you are dealing with in order to determine if special accommodations must be made.

Methodology

The method for determining the operating system is to start by looking for the platform. For the pur-

poses of this book, the platforms are divided into three groups: Windows, Macintosh, and Unix.

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