this method can be used to check if chrome extension is installed & enabled.
553505
function isChromeExtensionAvailable(callback) {
    if (!callback) return;
    if (chromeMediaSource == 'desktop') return callback(true);

    // ask extension if it is available
    window.postMessage('are-you-there', '*');
    setTimeout(function () {
        if (chromeMediaSource == 'screen') {
            callback(false);
        } else callback(true);
    }, 2000);
}
935817
public static function checkEnv()
    {
        if (function_exists('get_loaded_extensions')) {
            //Test curl extension
            $enabled_extension = array("curl");
            $extensions = get_loaded_extensions();
            if ($extensions) {
                foreach ($enabled_extension as $item) {
                    if (!in_array($item, $extensions)) {
                        throw new OssException("Extension {" . $item . "} is not installed or not enabled, please check your php env.");
                    }
                }
            } else {
                throw new OssException("function get_loaded_extensions not found.");
            }
        } else {
            throw new OssException('Function get_loaded_extensions has been disabled, please check php config.');
        }
    }
1127689
private boolean isProductExtensionInstalled(String inputString, String productExtension) {
        if ((productExtension == null) || (inputString == null)) {
            return false;
        }
        int msgIndex = inputString.indexOf("CWWKF0012I: The server installed the following features:");
        if (msgIndex == -1) {
            return false;
        }

        String msgString = inputString.substring(msgIndex);
        int leftBracketIndex = msgString.indexOf("[");
        int rightBracketIndex = msgString.indexOf("]");
        if ((leftBracketIndex == -1) ||
            (rightBracketIndex == -1) ||
            (rightBracketIndex < leftBracketIndex)) {
            return false;
        }

        String features = msgString.substring(leftBracketIndex, rightBracketIndex);
        Log.info(c, "isProductExtensionInstalled", features);
        if (features.indexOf(productExtension) == -1) {
            return false;
        }
        return true;
    }
1065334
function checkBrowser() {
	this.ver = navigator.appVersion
	this.dom = document.getElementById ? 1 : 0
	this.ie5 = (this.ver.indexOf("MSIE 5") > -1 && this.dom) ? 1 : 0;
	this.ie4 = (document.all && !this.dom) ? 1 : 0;
	this.ns5 = (this.dom && parseInt(this.ver) >= 5) ? 1 : 0;
	this.ns4 = (document.layers && !this.dom) ? 1 : 0;
	this.bw = (this.ie5 || this.ie4 || this.ns4 || this.ns5)
	return this
}
900722
def is_installed(self):
        
        return self.is_configured() and os.access(self.bin(), os.X_OK)
53824
private boolean checkForAddOnAccess() {
        Class[] classContext = getClassContext();
        for (Class clazz : classContext) {
            if (clazz.getClassLoader() instanceof IzouPluginClassLoader) {
                return true;
            }
        }
        return false;
    }
1289638
def is_installed():
  # type: () -> bool
  
  try:
    # noinspection PyUnresolvedReferences
    from ccurl import Curl as CCurl
  except ImportError:
    return False
  else:
    # noinspection PyUnresolvedReferences
    from iota.crypto import Curl
    return issubclass(Curl, CCurl)
560201
static boolean canBeLoaded(Map<Class<? extends Extension>, Extension> extensions, Extension extension) {
        return canBeLoaded(extensions, extension, new ArrayList<>());
    }
25275
def isApplicationInstalled(self, pchAppKey):
        """"""

        fn = self.function_table.isApplicationInstalled
        result = fn(pchAppKey)
        return result
1263319
def check(self):
        """"""
        return programs.is_module_installed(self.modname,
                                            self.required_version,
                                            self.installed_version)
1201901
public function isInstalled(string $name): bool
    {
        $extension = $this->getAvailableExtensions()->findByName($this->getNormalizedName($name));

        if ($extension instanceof ExtensionContract) {
            return $extension->isInstalled();
        }

        return false;
    }
131590
protected function determine() {
		$this->checkPlatform();
		$this->checkBrowsers();
		$this->checkForAol();
		$this->reduceVersion(); //modified for compatibility
		$this->checkPlatformVersion();	//add BugBuster
	}
540545
public static boolean check(Context context, WebView mWebView, boolean showInstall) {
        if (context == null) return false;

        boolean flashPluginExist = isPluginExist(context);

        if (mWebView != null) {
            if (!flashPluginExist && showInstall) {
                mWebView.addJavascriptInterface(new AndroidBridge(context), "android");
                String content = "<html>\n" +
                        "<head></head>\n" +
                        "<body>\n" +
                        "<br/><br/>\n" +
                        "\n" +
                        "<h3>Sorry, We have found that you haven't installed adobe flash player's plugin!</h3>\n" +
                        "\n" +
                        "<p>\n" +
                        "<h4>\n" +
                        "    You can click <a href=\"#\" onclick=\"window.android.goMarket()\"> <b> here</b></a> to\n" +
                        "    install it.</h4>\n" +
                        "</p>\n" +
                        "</body>\n" +
                        "</html>\n";
                mWebView.loadData(content, "text/html", "UTF-8");
            }
        }

        return flashPluginExist;
    }
898793
public static boolean isPackageInstalled(Context context, String packageName) {
		try {
			context.getPackageManager().getApplicationInfo(packageName, 0);
			return true;
		} catch (Exception e) {
			return false;
		}
	}
728738
public function checkInstallInput()
    {
       
        $defaults = array('extension' => null,
                          'data' => true);
                          
        $this->options = array_merge($defaults, $this->options);
        
        if ($this->options['extension'] == null){
            $this->error("Please provide the 'extension' parameter.", true);
        }
       
    }
1030971
protected function checkBrowserChrome() {
	    if( stripos($this->_agent,'Chrome') !== false ) {
		    $aresult = explode('/',stristr($this->_agent,'Chrome'));
		    $aversion = explode(' ',$aresult[1]);
		    $this->setVersion($aversion[0]);
		    $this->setBrowser(self::BROWSER_CHROME);
		    return true;
	    }
	    return false;
    }
556269
public boolean detectFirefoxOSTablet() {

        //First, let's make sure we're NOT on another major mobile OS.
        if (detectIos() || detectAndroid() || detectSailfish()) {
            return false;
        }

        if ((userAgent.indexOf(engineFirefox) != -1) && (userAgent.indexOf(deviceTablet) != -1)) {
            return true;
        }

        return false;
    }