WebReference.com - Part 1 of Chapter 6 from Designing with JavaScript (1/4)

Designing with JavaScript, 2nd Edition

What browser is that knocking at my door?

Before you learn how JavaScript differentiates between one browser and another, you need to understand how JavaScript gets information from the browser. This applies to both Netscape Navigator and Internet Explorer.

The navigator object

The navigator object provides information about the browser, regardless of whether the browser is Netscape Navigator, Internet Explorer, or any other browser.

JavaScript identifies browsers through the navigator object. Although "navigator" is the name of Netscape's browser, it serves the same function in IE's implementation of JavaScript. You can get a lot of information from the navigator object, and we'll cover it all in this chapter. Table 6-1 shows three of the more useful properties for getting information about browsers, versions, and operating systems.

Property	What it refers to
`navigator.appName`	The browser's name
`navigator.appVersion`	The browser's version
`navigator.userAgent`	The browser's "user agent"--the official term for a web browser or a web-capable reader, like a handheld device or WebTV

Table 6-1: Properties of the browser object

Without any context, the significance of these properties may not be clear. Table 6-2 shows some examples of what you actually get when you use these properties on different browsers. Note that this list isn't comprehensive; it just shows the properties for a handful of configurations, including some that are mostly of historical interest.

Browser	`appName`	`appVersion`	`userAgent`
Netscape 3.01 on a Mac	Netscape	3.01 (Macintosh; I; PPC)	Mozilla/3.01 (Macintosh; PPC)
Netscape 4.0 on Windows 95	Netscape	4.0 (Win95; I)	Mozilla/4.0 (Win95; I)
Netscape 4.72 on Windows 98	Netscape	4.72 [en] (Win98; U)	Mozilla/4.72 [en] (Win98; U)
Netscape 6.01 on Windows Me	Netscape	5.0 (Windows; en-US)	Mozilla/5.0 (Windows; U; Win 9x 4.90; en-US; m18) Gecko/ 20010131 Netscape6/6.01
Internet Explorer 3.0 on Windows 95	Microsoft Internet Explorer	2.0 (compatible; MSIE 3.01; Windows 95)	Mozilla/2.0 (compatible; MSIE 3.01; Windows 95)
Internet Explorer 4.0 on Windows 95	Microsoft Internet Explorer	4.0 (compatible; MSIE 4.0; Windows 95)	Mozilla/4.0 (compatible; MSIE 4.0; Windows 95)
Internet Explorer 5.0 on a Mac	Microsoft Internet Explorer	4.0 (compatible; MSIE 5.0; Macintosh; I; PPC)	Mozilla/4.0 (compatible; MSIE 5.0; Mac_PowerPC)
Internet Explorer 5.5 on Windows Me	Microsoft Internet Explorer	4.0 (compatible; MSIE 5.5; Windows 98; Win 9x 4.90)	Mozilla/4.0 (compatible; MSIE 5.5; Windows 98; Win 9x 4.90)
Internet Explorer 6.0 on Windows 2000	Microsoft Internet Explorer	4.0 (compatible; MSIE 6.0; Windows NT 5.0)	Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)