Detecting Java version (runnable in browser) with JavaScript?

Question

I was checking this code provided by Sun that can retrieve a list of the Java Runtime Environments installed on the machine. Here's the code formatted and with some functions removed so it's easier to read:

var deployJava = {
    debug: null,
    firefoxJavaVersion: null,
    returnPage: null,
    locale: null,
    oldMimeType: 'application/npruntime-scriptable-plugin;DeploymentToolkit',
    mimeType: 'application/java-deployment-toolkit',
    browserName: null,
    browserName2: null,
    getJREs: function () {
        var list = new Array();
        if (deployJava.isPluginInstalled()) {
            var plugin = deployJava.getPlugin();
            var VMs = plugin.jvms;
            for (var i = 0; i < VMs.getLength(); i++) {
                list[i] = VMs.get(i).version;
            }
        } else {
            var browser = deployJava.getBrowser();
            if (browser == 'MSIE') {
                if (deployJava.testUsingActiveX('1.7.0')) {
                    list[0] = '1.7.0';
                } else if (deployJava.testUsingActiveX('1.6.0')) {
                    list[0] = '1.6.0';
                } else if (deployJava.testUsingActiveX('1.5.0')) {
                    list[0] = '1.5.0';
                } else if (deployJava.testUsingActiveX('1.4.2')) {
                    list[0] = '1.4.2';
                } else if (deployJava.testForMSVM()) {
                    list[0] = '1.1';
                }
            } else if (browser == 'Netscape Family') {
                deployJava.getJPIVersionUsingMimeType();
                if (deployJava.firefoxJavaVersion != null) {
                    list[0] = deployJava.firefoxJavaVersion;
                } else if (deployJava.testUsingMimeTypes('1.7')) {
                    list[0] = '1.7.0';
                } else if (deployJava.testUsingMimeTypes('1.6')) {
                    list[0] = '1.6.0';
                } else if (deployJava.testUsingMimeTypes('1.5')) {
                    list[0] = '1.5.0';
                } else if (deployJava.testUsingMimeTypes('1.4.2')) {
                    list[0] = '1.4.2';
                } else if (deployJava.browserName2 == 'Safari') {
                    if (deployJava.testUsingPluginsArray('1.7.0')) {
                        list[0] = '1.7.0';
                    } else if (deployJava.testUsingPluginsArray('1.6')) {
                        list[0] = '1.6.0';
                    } else if (deployJava.testUsingPluginsArray('1.5')) {
                        list[0] = '1.5.0';
                    } else if (deployJava.testUsingPluginsArray('1.4.2')) {
                        list[0] = '1.4.2';
                    }
                }
            }
        }
        if (deployJava.debug) {
            for (var i = 0; i < list.length; ++i) {
                alert('We claim to have detected Java SE ' + list[i]);
            }
        }
        return list;
    },
    runApplet: function (attributes, parameters, minimumVersion) {
        if (minimumVersion == 'undefined' || minimumVersion == null) {
            minimumVersion = '1.1';
        }
        var regex = "^(\\d+)(?:\\.(\\d+)(?:\\.(\\d+)(?:_(\\d+))?)?)?$";
        var matchData = minimumVersion.match(regex);
        if (deployJava.returnPage == null) {
            deployJava.returnPage = document.location;
        }
        if (matchData != null) {
            var browser = deployJava.getBrowser();
            if ((browser != '?') && ('Safari' != deployJava.browserName2)) {
                if (deployJava.versionCheck(minimumVersion + '+')) {
                    deployJava.writeAppletTag(attributes, parameters);
                }
            } else {
                deployJava.writeAppletTag(attributes, parameters);
            }
        } else {
            if (deployJava.debug) {
                alert('Invalid minimumVersion argument to runApplet():' + minimumVersion);
            }
        }
    },
    writeAppletTag: function (attributes, parameters) {
        var startApplet = '<' + 'applet ';
        var params = '';
        var endApplet = '<' + '/' + 'applet' + '>';
        var addCodeAttribute = true;
        for (var attribute in attributes) {
            startApplet += (' ' + attribute + '="' + attributes[attribute] + '"');
            if (attribute == 'code' || attribute == 'java_code') {
                addCodeAttribute = false;
            }
        }
        if (parameters != 'undefined' && parameters != null) {
            var codebaseParam = false;
            for (var parameter in parameters) {
                if (parameter == 'codebase_lookup') {
                    codebaseParam = true;
                }
                if (parameter == 'object' || parameter == 'java_object') {
                    addCodeAttribute = false;
                }
                params += '<param name="' + parameter + '" value="' + parameters[parameter] + '"/>';
            }
            if (!codebaseParam) {
                params += '<param name="codebase_lookup" value="false"/>';
            }
        }
        if (addCodeAttribute) {
            startApplet += (' code="dummy"');
        }
        startApplet += '>';
        document.write(startApplet + '\n' + params + '\n' + endApplet);
    },
    versionCheck: function (versionPattern) {
        var index = 0;
        var regex = "^(\\d+)(?:\\.(\\d+)(?:\\.(\\d+)(?:_(\\d+))?)?)?(\\*|\\+)?$";
        var matchData = versionPattern.match(regex);
        if (matchData != null) {
            var familyMatch = true;
            var patternArray = new Array();
            for (var i = 1; i < matchData.length; ++i) {
                if ((typeof matchData[i] == 'string') && (matchData[i] != '')) {
                    patternArray[index] = matchData[i];
                    index++;
                }
            }
            if (patternArray[patternArray.length - 1] == '+') {
                familyMatch = false;
                patternArray.length--;
            } else {
                if (patternArray[patternArray.length - 1] == '*') {
                    patternArray.length--;
                }
            }
            var list = deployJava.getJREs();
            for (var i = 0; i < list.length; ++i) {
                if (deployJava.compareVersionToPattern(list[i], patternArray, familyMatch)) {
                    return true;
                }
            }
            return false;
        } else {
            alert('Invalid versionPattern passed to versionCheck: ' + versionPattern);
            return false;
        }
    },
    isWebStartInstalled: function (minimumVersion) {
        var browser = deployJava.getBrowser();
        if ((browser == '?') || ('Safari' == deployJava.browserName2)) {
            return true;
        }
        if (minimumVersion == 'undefined' || minimumVersion == null) {
            minimumVersion = '1.4.2';
        }
        var retval = false;
        var regex = "^(\\d+)(?:\\.(\\d+)(?:\\.(\\d+)(?:_(\\d+))?)?)?$";
        var matchData = minimumVersion.match(regex);
        if (matchData != null) {
            retval = deployJava.versionCheck(minimumVersion + '+');
        } else {
            if (deployJava.debug) {
                alert('Invalid minimumVersion argument to isWebStartInstalled(): ' + minimumVersion);
            }
            retval = deployJava.versionCheck('1.4.2+');
        }
        return retval;
    },
    getJPIVersionUsingMimeType: function () {
        for (var i = 0; i < navigator.mimeTypes.length; ++i) {
            var s = navigator.mimeTypes[i].type;
            var m = s.match(/^application\/x-java-applet;jpi-version=(.*)$/);
            if (m != null) {
                deployJava.firefoxJavaVersion = m[1];
                if ('Opera' != deployJava.browserName2) {
                    break;
                }
            }
        }
    },
    isPluginInstalled: function () {
        var plugin = deployJava.getPlugin();
        if (plugin && plugin.jvms) {
            return true;
        } else {
            return false;
        }
    },
    isPlugin2: function () {
        if (deployJava.isPluginInstalled()) {
            if (deployJava.versionCheck('1.6.0_10+')) {
                try {
                    return deployJava.getPlugin().isPlugin2();
                } catch (err) {}
            }
        }
        return false;
    },
    allowPlugin: function () {
        deployJava.getBrowser();
        var ret = ('Safari' != deployJava.browserName2 && 'Opera' != deployJava.browserName2);
        return ret;
    },
    getPlugin: function () {
        deployJava.refresh();
        var ret = null;
        if (deployJava.allowPlugin()) {
            ret = document.getElementById('deployJavaPlugin');
        }
        return ret;
    },
    compareVersionToPattern: function (version, patternArray, familyMatch) {
        var regex = "^(\\d+)(?:\\.(\\d+)(?:\\.(\\d+)(?:_(\\d+))?)?)?$";
        var matchData = version.match(regex);
        if (matchData != null) {
            var index = 0;
            var result = new Array();
            for (var i = 1; i < matchData.length; ++i) {
                if ((typeof matchData[i] == 'string') && (matchData[i] != '')) {
                    result[index] = matchData[i];
                    index++;
                }
            }
            var l = Math.min(result.length, patternArray.length);
            if (familyMatch) {
                for (var i = 0; i < l; ++i) {
                    if (result[i] != patternArray[i]) return false;
                }
                return true;
            } else {
                for (var i = 0; i < l; ++i) {
                    if (result[i] < patternArray[i]) {
                        return false;
                    } else if (result[i] > patternArray[i]) {
                        return true;
                    }
                }
                return true;
            }
        } else {
            return false;
        }
    },
    getBrowser: function () {
        if (deployJava.browserName == null) {
            var browser = navigator.userAgent.toLowerCase();
            if (deployJava.debug) {
                alert('userAgent -> ' + browser);
            }
            if (browser.indexOf('msie') != -1) {
                deployJava.browserName = 'MSIE';
                deployJava.browserName2 = 'MSIE';
            } else if (browser.indexOf('iphone') != -1) {
                deployJava.browserName = 'Netscape Family';
                deployJava.browserName2 = 'iPhone';
            } else if (browser.indexOf('firefox') != -1) {
                deployJava.browserName = 'Netscape Family';
                deployJava.browserName2 = 'Firefox';
            } else if (browser.indexOf('chrome') != -1) {
                deployJava.browserName = 'Netscape Family';
                deployJava.browserName2 = 'Chrome';
            } else if (browser.indexOf('safari') != -1) {
                deployJava.browserName = 'Netscape Family';
                deployJava.browserName2 = 'Safari';
            } else if (browser.indexOf('mozilla') != -1) {
                deployJava.browserName = 'Netscape Family';
                deployJava.browserName2 = 'Other';
            } else if (browser.indexOf('opera') != -1) {
                deployJava.browserName = 'Netscape Family';
                deployJava.browserName2 = 'Opera';
            } else {
                deployJava.browserName = '?';
                deployJava.browserName2 = 'unknown';
            }
            if (deployJava.debug) {
                alert('Detected browser name:' + deployJava.browserName + ', ' + deployJava.browserName2);
            }
        }
        return deployJava.browserName;
    },
    testUsingActiveX: function (version) {
        var objectName = 'JavaWebStart.isInstalled.' + version + '.0';
        if (!ActiveXObject) {
            if (deployJava.debug) {
                alert('Browser claims to be IE, but no ActiveXObject object?');
            }
            return false;
        }
        try {
            return (new ActiveXObject(objectName) != null);
        } catch (exception) {
            return false;
        }
    },
    testForMSVM: function () {
        var clsid = '{08B0E5C0-4FCB-11CF-AAA5-00401C608500}';
        if (typeof oClientCaps != 'undefined') {
            var v = oClientCaps.getComponentVersion(clsid, "ComponentID");
            if ((v == '') || (v == '5,0,5000,0')) {
                return false;
            } else {
                return true;
            }
        } else {
            return false;
        }
    },
    testUsingMimeTypes: function (version) {
        if (!navigator.mimeTypes) {
            if (deployJava.debug) {
                alert('Browser claims to be Netscape family, but no mimeTypes[] array?');
            }
            return false;
        }
        for (var i = 0; i < navigator.mimeTypes.length; ++i) {
            s = navigator.mimeTypes[i].type;
            var m = s.match(/^application\/x-java-applet\x3Bversion=(1\.8|1\.7|1\.6|1\.5|1\.4\.2)$/);
            if (m != null) {
                if (deployJava.compareVersions(m[1], version)) {
                    return true;
                }
            }
        }
        return false;
    },
    testUsingPluginsArray: function (version) {
        if ((!navigator.plugins) || (!navigator.plugins.length)) {
            return false;
        }
        var platform = navigator.platform.toLowerCase();
        for (var i = 0; i < navigator.plugins.length; ++i) {
            s = navigator.plugins[i].description;
            if (s.search(/^Java Switchable Plug-in (Cocoa)/) != -1) {
                if (deployJava.compareVersions("1.5.0", version)) {
                    return true;
                }
            } else if (s.search(/^Java/) != -1) {
                if (platform.indexOf('win') != -1) {
                    if (deployJava.compareVersions("1.5.0", version) || deployJava.compareVersions("1.6.0", version)) {
                        return true;
                    }
                }
            }
        }
        if (deployJava.compareVersions("1.5.0", version)) {
            return true;
        }
        return false;
    },
    compareVersions: function (installed, required) {
        var a = installed.split('.');
        var b = required.split('.');
        for (var i = 0; i < a.length; ++i) {
            a[i] = Number(a[i]);
        }
        for (var i = 0; i < b.length; ++i) {
            b[i] = Number(b[i]);
        }
        if (a.length == 2) {
            a[2] = 0;
        }
        if (a[0] > b[0]) return true;
        if (a[0] < b[0]) return false;
        if (a[1] > b[1]) return true;
        if (a[1] < b[1]) return false;
        if (a[2] > b[2]) return true;
        if (a[2] < b[2]) return false;
        return true;
    },
    enableAlerts: function () {
        deployJava.browserName = null;
        deployJava.debug = true;
    },
    writePluginTag: function () {
        var browser = deployJava.getBrowser();
        if (browser == 'MSIE') {
            document.write('<' + 'object classid="clsid:CAFEEFAC-DEC7-0000-0000-ABCDEFFEDCBA" ' + 'id="deployJavaPlugin" width="0" height="0">' + '<' + '/' + 'object' + '>');
        } else if (browser == 'Netscape Family' && deployJava.allowPlugin()) {
            deployJava.writeEmbedTag();
        }
    },
    refresh: function () {
        navigator.plugins.refresh(false);
        var browser = deployJava.getBrowser();
        if (browser == 'Netscape Family' && deployJava.allowPlugin()) {
            var plugin = document.getElementById('deployJavaPlugin');
            if (plugin == null) {
                deployJava.writeEmbedTag();
            }
        }
    },
    writeEmbedTag: function () {
        var written = false;
        if (navigator.mimeTypes != null) {
            for (var i = 0; i < navigator.mimeTypes.length; i++) {
                if (navigator.mimeTypes[i].type == deployJava.mimeType) {
                    if (navigator.mimeTypes[i].enabledPlugin) {
                        document.write('<' + 'embed id="deployJavaPlugin" type="' + deployJava.mimeType + '" hidden="true" />');
                        written = true;
                    }
                }
            }
            if (!written) for (var i = 0; i < navigator.mimeTypes.length; i++) {
                if (navigator.mimeTypes[i].type == deployJava.oldMimeType) {
                    if (navigator.mimeTypes[i].enabledPlugin) {
                        document.write('<' + 'embed id="deployJavaPlugin" type="' + deployJava.oldMimeType + '" hidden="true" />');
                    }
                }
            }
        }
    },
    do_initialize: function () {
        deployJava.writePluginTag();
        if (deployJava.locale == null) {
            var loc = null;
            if (loc == null) try {
                loc = navigator.userLanguage;
            } catch (err) {}
            if (loc == null) try {
                loc = navigator.systemLanguage;
            } catch (err) {}
            if (loc == null) try {
                loc = navigator.language;
            } catch (err) {}
            if (loc != null) {
                loc.replace("-", "_")
                deployJava.locale = loc;
            }
        }
    }
};
deployJava.do_initialize();

But I've read regarding this code:

...if you have both a Sun JRE and MSJVM installed, the toolkit will report the Sun JRE version even if it's disabled and the browser will actually run MSJVM...

The second problem with that code is that it retrieves a list of the installed JREs, and I only care about the one that will open the Applet I need to deploy inside the browser.

Does someone knows a pure js method to get the version of Java that would run in the browser if I try load an Applet?