title: Detect if browser extension is installed for Opera
body: <p>I have created browser extension/add-on for Chrome, Firefox, Safari and IE using <code>Crossrider framework</code><br>
  Now since Crossrider does not provide support for Opera, I have created a native extension for the same.<br>
  My problem is how to detect if a user(using Opera), visiting our website, has the extension installed or not ?</p>
  
  <p><a href="https://stackoverflow.com/questions/14398548/javascript-check-if-browser-extension-is-installed-for-chrome-firefox-and-opera">Similar Question</a> is answered. Is there any better option?   </p>
  
  <p>Or any simple way to check(<strong>crossbrowser</strong>) if an extension is installed or not so that I don't have to use <code>Crossrider.API</code>?</p>
  
  <p>Or is there anything similar to <a href="https://developer.mozilla.org/en/DOM/window.navigator.plugins" rel="nofollow noreferrer">window.navigator.plugins</a> for extensions?</p>