Provide callbacks in serviceWorker (next) (facebook#3867)

* Provide callbacks in serviceWorker * revert exporting default function

Author: piotr-cz

packages/react-scripts/template/src/serviceWorker.js

@@ -18,7 +18,7 @@ const isLocalhost = Boolean(
  )
 );
 
-export function register() {
+export function register(config) {
  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);
@@ -34,7 +34,7 @@ export function register() {
 
  if (isLocalhost) {
  // This is running on localhost. Lets check if a service worker still exists or not.
- checkValidServiceWorker(swUrl);
+ checkValidServiceWorker(swUrl, config);
 
  // Add some additional logging to localhost, pointing developers to the
  // service worker/PWA documentation.
@@ -46,13 +46,13 @@ export function register() {
  });
  } else {
  // Is not local host. Just register service worker
- registerValidSW(swUrl);
+ registerValidSW(swUrl, config);
  }
  });
  }
 }
 
-function registerValidSW(swUrl) {
+function registerValidSW(swUrl, config) {
  navigator.serviceWorker
  .register(swUrl)
  .then(registration => {
@@ -66,11 +66,21 @@ function registerValidSW(swUrl) {
  // 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.');
+
+ // Execute callback
+ if (config.onUpdate) {
+ config.onUpdate(registration);
+ }
  } 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.');
+
+ // Execute callback
+ if (config.onSuccess) {
+ config.onSuccess(registration);
+ }
  }
  }
  };
@@ -81,7 +91,7 @@ function registerValidSW(swUrl) {
  });
 }
 
-function checkValidServiceWorker(swUrl) {
+function checkValidServiceWorker(swUrl, config) {
  // Check if the service worker can be found. If it can't reload the page.
  fetch(swUrl)
  .then(response => {
@@ -98,7 +108,7 @@ function checkValidServiceWorker(swUrl) {
  });
  } else {
  // Service worker found. Proceed as normal.
- registerValidSW(swUrl);
+ registerValidSW(swUrl, config);
  }
  })
  .catch(() => {