How to check JRE version of client machine with Javascript

The example below checks if a user has JRE version 1.6.0_13 or greater installed. If not, it installs the latest JRE.

<script src="http://java.com/js/deployJava.js"></script>
<script>
    
    // check if current JRE version is greater than 1.6.0 
    alert("versioncheck " + deployJava.versionCheck('1.6.0_10+'));
    if (deployJava.versionCheck('1.6.0_10+') == false) {                   
        userInput = confirm("You need the latest Java(TM) Runtime Environment. Would you like to update now?");        
        if (userInput == true) {  
    
            // Set deployJava.returnPage to make sure user comes back to 
            // your web site after installing the JRE
            deployJava.returnPage = location.href;
            
            // install latest JRE or redirect user to another page to get JRE from.
            deployJava.installLatestJRE(); 
        }
    }
</script>