↑
Main Page

Methodology

The Browser Detection Script

The browser detection script described in this section uses the user-agent string detection to identify the

following browsers:

Opera 4.0 and higher

Internet Explorer 4.0 and higher

Mozilla 0.9.2 and higher

Safari 1.0 and higher

Netscape Navigator 4.0 – 4.8x

In addition, the methods developed in this chapter fail gracefully and do not cause JavaScript errors in

older browsers that perhaps don’t support ECMAScript Edition 3 fully.

Methodology

To be practical, it is necessary to detect minimal versions of browsers instead of exact versions. For

instance, this code detects exact versions:

if (isIE5 || isIE6) {

//code

}

It may not seem like a problem now, but what if IE gets up to version 10? You would be required to keep

adding to this code:

if (isIE5 || isIE6 || isIE7 || isIE8 || isIE9 || isIE10) {

//code

}

This obviously is not optimal. However, if you test for minimal versions of browsers, the test remains

the same regardless of how many future versions are released:

if (isMinIE5) {

//code

}

This algorithm never changes, and it represents the way that the browser detection code in this chapter

is developed.

First Steps

The first two steps necessary for browser detection are storing the user-agent string in a local variable

and getting the reported browser version:

var sUserAgent = navigator.userAgent;

var fAppVersion = parseFloat(navigator.appVersion);

234

Chapter 8

11_579088 ch08.qxd 3/28/05 11:38 AM Page 234