added registersw.js test

Author: Developerayo

src/registerServiceWorker.js

@@ -0,0 +1,100 @@
+// Leave this file alone, I'm just testing something, not part of the project.
+// You can delete this file if you like.
+const 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}$/
+      )
+  );
+  
+  export default function register() {
+    if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
+      // The URL constructor is available in all browsers that support SW.
+      const publicUrl = new URL(process.env.PUBLIC_URL, window.location);
+      if (publicUrl.origin !== window.location.origin) {
+        // Our service worker won't work if PUBLIC_URL is on a different origin
+        // from what our page is served on. This might happen if a CDN is used to
+        // serve assets; see https://github.com/facebookincubator/create-react-app/issues/2374
+        return;
+      }
+  
+      window.addEventListener('load', () => {
+        const swUrl = `${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);
+        } else {
+          // Is not local host. Just register service worker
+          registerValidSW(swUrl);
+        }
+      });
+    }
+  }
+  
+  function registerValidSW(swUrl) {
+    navigator.serviceWorker
+      .register(swUrl)
+      .then(registration => {
+        registration.onupdatefound = () => {
+          const installingWorker = registration.installing;
+          installingWorker.onstatechange = () => {
+            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(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(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(registration => {
+            registration.unregister().then(() => {
+              window.location.reload();
+            });
+          });
+        } else {
+          // Service worker found. Proceed as normal.
+          registerValidSW(swUrl);
+        }
+      })
+      .catch(() => {
+        console.log(
+          'No internet connection found. App is running in offline mode.'
+        );
+      });
+  }
+  
+  export function unregister() {
+    if ('serviceWorker' in navigator) {
+      navigator.serviceWorker.ready.then(registration => {
+        registration.unregister();
+      });
+    }
+  }