The Navigator Object 導航對象 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導航對象包含所有有關訪問這者瀏覽器的信息。我們將看看兩個導航對象的產物：
appName - holds the name of the browser appName - 含瀏覽器的名稱 appVersion - holds, among other things, the version of the browser appVersion - 瀏覽器版本 Example 舉例
The variable browser in the example above holds the name of the browser, i.e. "Netscape" or "Microsoft Internet Explorer". 上面例子中變量brower(瀏覽器)被賦加了瀏覽器的名稱，網景或是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屬性返回一串包含比版本號更多的信息字符，但現在我們只要版本號。要從字符串中提出版本號我們使用一個叫parseFloat()的函數來返回數字。
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. （有關JS返回IE版本號的問題）
Example 舉例 The script below displays a different alert, depending on the visitor's browser: 根據訪問者的瀏覽器，（不同的瀏覽器）下面的腳本將顯示不同的警示：
