On Mac OS X, one can not use the functioned offered in public http://java.com/js/deployJava.js to detect if java plug-in installed

Both of these functions returned false on Mac OS X with jre 9 installed

/*returns true if the ActiveX or XPI plugin is installed */
deployJava.isPluginInstalled()

/*Determines if the next generation plugin (Plugin II) is default */
deployJava.isPlugin2()