The Navigator Object 导航对象 The JavaScript Navigator object contains all information about the visitor's browser. We are going to look at two properties of the Navigator object: JS导航对象包含所有有关访问这者浏览器的信息。我们将看看两个导航对象的产物：
appName - holds the name of the browser appName - 含浏览器的名称 appVersion - holds, among other things, the version of the browser appVersion - 浏览器版本 Example 举例
[Ctrl+A 全选 注:如需引入外部Js需刷新才能执行]
The variable browser in the example above holds the name of the browser, i.e. "Netscape" or "Microsoft Internet Explorer". 上面例子中变量brower(浏览器)被赋加了浏览器的名称，网景或是IE(或其他)
The appVersion property in the example above returns a string that contains much more information than just the version number, but for now we are only interested in the version number. To pull the version number out of the string we are using a function called parseFloat(), which pulls the first thing that looks like a decimal number out of a string and returns it. 上面例子中的appVersion属性返回一串包含比版本号更多的信息字符，但现在我们只要版本号。要从字符串中提出版本号我们使用一个叫parseFloat()的函数来返回数字。
IMPORTANT! The version number is WRONG in IE 5.0 or later! Microsoft start the appVersion string with the numbers 4.0. in IE 5.0 and IE 6.0!!! Why did they do that??? However, JavaScript is the same in IE6, IE5 and IE4, so for most scripts it is ok. （有关JS返回IE版本号的问题）
Example 举例 The script below displays a different alert, depending on the visitor's browser: 根据访问者的浏览器，（不同的浏览器）下面的脚本将显示不同的警示：