Navigator 3.0
navigator.javaEnabled()
None.
true if, and only if, Java is supported by and enabled on the current browser.
You can use navigator.javaEnabled() to check whether the current browser will be able to display applets, and also whether JavaScript will be able to work with Java objects through the Properties object. If Java is not available, you can use JavaScript to perform some alternative action.
"Document.applets[]", "Navigator", Properties