docs: update type-casting of "self" without re-declaration in service-worker (#13624)

* Update typing of "self" without redeclaration in serviceworker

* use self = globalThis.self trick

---------

Co-authored-by: Chew Tee Ming <[email protected]>
Co-authored-by: Rich Harris <[email protected]>

Author: 3 people

documentation/docs/30-advanced/40-service-workers.md

@@ -38,9 +38,8 @@ The following example caches the built app and any files in `static` eagerly, an
 
 import { build, files, version } from '$service-worker';
 
-// The reassignment of `self` to `sw` allows you to type cast it in the process
-// (this is the easiest way to do it without needing additional files)
-const sw = /** @type {ServiceWorkerGlobalScope} */ (/** @type {unknown} */ (self));
+// This gives `self` the correct types
+const self = /** @type {ServiceWorkerGlobalScope} */ (/** @type {unknown} */ (globalThis.self));
 
 // Create a unique cache name for this deployment
 const CACHE = `cache-${version}`;
@@ -50,7 +49,7 @@ const ASSETS = [
 	...files  // everything in `static`
 ];
 
-sw.addEventListener('install', (event) => {
+self.addEventListener('install', (event) => {
 	// Create a new cache and add all files to it
 	async function addFilesToCache() {
 		const cache = await caches.open(CACHE);
@@ -60,7 +59,7 @@ sw.addEventListener('install', (event) => {
 	event.waitUntil(addFilesToCache());
 });
 
-sw.addEventListener('activate', (event) => {
+self.addEventListener('activate', (event) => {
 	// Remove previous cached data from disk
 	async function deleteOldCaches() {
 		for (const key of await caches.keys()) {
@@ -71,7 +70,7 @@ sw.addEventListener('activate', (event) => {
 	event.waitUntil(deleteOldCaches());
 });
 
-sw.addEventListener('fetch', (event) => {
+self.addEventListener('fetch', (event) => {
 	// ignore POST requests etc
 	if (event.request.method !== 'GET') return;