Fix tslint

Author: William Monk

packages/react-scripts/template/src/registerServiceWorker.ts

@@ -1,8 +1,9 @@
+// tslint:disable:no-console
 // 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
+// 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.
@@ -21,7 +22,10 @@ const isLocalhost = Boolean(
 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);
+    const publicUrl = new URL(
+      process.env.PUBLIC_URL,
+      window.location.toString()
+    );
     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
@@ -43,43 +47,45 @@ export default function register() {
   }
 }
 
-function registerValidSW(swUrl) {
+function registerValidSW(swUrl: string) {
   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.');
+        if (installingWorker) {
+          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) {
+function checkValidServiceWorker(swUrl: string) {
   // 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
+        response.headers.get('content-type')!.indexOf('javascript') === -1
       ) {
         // No service worker found. Probably a different app. Reload the page.
         navigator.serviceWorker.ready.then(registration => {