Window.isSecureContext

The window.isSecureContext read-only property indicates whether a context is capable of using features that require secure contexts.

You can use feature detection to check whether they are in a secure context or not by using the isSecureContext boolean which is exposed on the global scope.

if (window.isSecureContext) {
  // Page is a secure context so service workers are now available
  navigator.serviceWorker.register("/offline-worker.js").then(function () {
    ...
  });
}

• Secure contexts