firefox/devtools/shared/network-observer/test/browser/doc_network-observer.html

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     http://creativecommons.org/publicdomain/zero/1.0/ -->
<!doctype html>

<html>
  <head>
    <meta charset="utf-8"/>
    <meta http-equiv="Cache-Control" content="no-cache, no-store, must-revalidate" />
    <meta http-equiv="Pragma" content="no-cache" />
    <meta http-equiv="Expires" content="0" />
    <title>Network Observer test page</title>
  </head>
  <body>
    <p>Network Observer test page</p>
    <script type="text/javascript">
      /* exported registerServiceWorker, unregisterServiceWorker */
      "use strict";

        let swRegistration;

        function registerServiceWorker() {
          const sw = navigator.serviceWorker;
          return sw.register("serviceworker.js")
            .then(registration => {
              swRegistration = registration;
              console.log("Registered, scope is:", registration.scope);
              return sw.ready;
            }).then(() => {
              // wait until the page is controlled
              return new Promise(resolve => {
                if (sw.controller) {
                  resolve();
                } else {
                  sw.addEventListener("controllerchange", function () {
                    resolve();
                  }, { once: true });
                }
              });
            }).catch(() => {
              console.error("Registration failed");
            });
        }

        function unregisterServiceWorker() {
          return swRegistration.unregister();
        }
    </script>
  </body>
</html>