如果要检测的JavaScript在浏览器中，你也许可以使用集合navigator.plugins。它与Firefox，Opera和Chrome浏览器，但遗憾的是没有与IE浏览器。

If you want to detect with javascript inside the browser, you can probably use the collection "navigator.plugins". It works with Firefox, Opera and Chrome but unfortunately not with IE.

更新： 在FF，Opera和Chrome浏览器，你可以很容易地测试它是这样的：

Update: In FF, Opera and Chrome you can test it easily like this:

if (navigator.plugins["Adobe Acrobat"]) {
// do some stuff if it is installed
} else {
// do some other stuff if its not installed
}

更新＃2： 如果是在IE中的ActiveX对象，你可以测试是否存在通过使用这样的：

Update #2: If it is an ActiveX object in IE you can test if it exists by using something like this:

function getActiveXObject(name){
    	try{
    		return new ActiveXObject(name);
    	}
    	catch(err){
    		return undefined;
    	}
};

有关IE另一种方法是类似于JohnFx建议的东西（我发现它这里和有没有测试过）：

Another approach for IE is something similar to what JohnFx suggested (I found it here and have not tested it):

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\Curr entVersion\Internet
Settings\User Agent\Post Platform