comment/lib/registerServiceWorker.js

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = register;
exports.unregister = unregister;
// In production, we register a service worker to serve assets from local cache.

// This lets the app load faster on subsequent visits in production, and gives
// it offline capabilities. However, it also means that developers (and users)
// will only see deployed updates on the "N+1" visit to a page, since previously
// cached resources are updated in the background.

// To learn more about the benefits of this model, read https://goo.gl/KwvDNy.
// This link also includes instructions on opting out of this behavior.

var isLocalhost = Boolean(window.location.hostname === "localhost" ||
// [::1] is the IPv6 localhost address.
window.location.hostname === "[::1]" ||
// 127.0.0.1/8 is considered localhost for IPv4.
window.location.hostname.match(/^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/));

function register() {
  if (process.env.NODE_ENV === "production" && "serviceWorker" in navigator) {
    // The URL constructor is available in all browsers that support SW.
    var publicUrl = new URL(process.env.PUBLIC_URL, window.location);
    if (publicUrl.origin !== window.location.origin) {
      // Our service worker won't work if PUBLIC_URL is on a different origin
      // from what our page is served on. This might happen if a CDN is used to
      // serve assets; see https://github.com/facebookincubator/create-react-app/issues/2374
      return;
    }

    window.addEventListener("load", function () {
      var swUrl = process.env.PUBLIC_URL + "/service-worker.js";

      if (isLocalhost) {
        // This is running on localhost. Lets check if a service worker still exists or not.
        checkValidServiceWorker(swUrl);

        // Add some additional logging to localhost, pointing developers to the
        // service worker/PWA documentation.
        navigator.serviceWorker.ready.then(function () {
          console.log("This web app is being served cache-first by a service " + "worker. To learn more, visit https://goo.gl/SC7cgQ");
        });
      } else {
        // Is not local host. Just register service worker
        registerValidSW(swUrl);
      }
    });
  }
}

function registerValidSW(swUrl) {
  navigator.serviceWorker.register(swUrl).then(function (registration) {
    registration.onupdatefound = function () {
      var installingWorker = registration.installing;
      installingWorker.onstatechange = function () {
        if (installingWorker.state === "installed") {
          if (navigator.serviceWorker.controller) {
            // At this point, the old content will have been purged and
            // the fresh content will have been added to the cache.
            // It's the perfect time to display a "New content is
            // available; please refresh." message in your web app.
            console.log("New content is available; please refresh.");
          } else {
            // At this point, everything has been precached.
            // It's the perfect time to display a
            // "Content is cached for offline use." message.
            console.log("Content is cached for offline use.");
          }
        }
      };
    };
  }).catch(function (error) {
    console.error("Error during service worker registration:", error);
  });
}

function checkValidServiceWorker(swUrl) {
  // Check if the service worker can be found. If it can't reload the page.
  fetch(swUrl).then(function (response) {
    // Ensure service worker exists, and that we really are getting a JS file.
    if (response.status === 404 || response.headers.get("content-type").indexOf("javascript") === -1) {
      // No service worker found. Probably a different app. Reload the page.
      navigator.serviceWorker.ready.then(function (registration) {
        registration.unregister().then(function () {
          window.location.reload();
        });
      });
    } else {
      // Service worker found. Proceed as normal.
      registerValidSW(swUrl);
    }
  }).catch(function () {
    console.log("No internet connection found. App is running in offline mode.");
  });
}

function unregister() {
  if ("serviceWorker" in navigator) {
    navigator.serviceWorker.ready.then(function (registration) {
      registration.unregister();
    });
  }
}
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