code: 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);
  }
docs: this method can be used to check if chrome extension is installed & enabled.