java plugin detection from javascript

From javascript how to detect the following plugin is installed on the system or not开发者_StackOverflow中文版

http://www.java.com/en/download/

---

Here's the official java deployment toolkit script.

Check out the "versionCheck" method.

Doc: http://download.oracle.com/javase/6/docs/technotes/guides/jweb/deployment_advice.html