https://www.voachinese.com/Scripts/responsive/serviceWorkerInstall.js?cb=323

1// register service worker if supported
2// Service-worker file needs to exist in root folder, because it defines its scope = it can intercept only requests below it in the tree structure
3
4window.addEventListener('load', async function () {
5    if ('serviceWorker' in navigator &&
6        (pwaEnabled || !swCacheDisabled)) {
7        var controler = await navigator.serviceWorker.controller;
8        var scriptUrl = controler ? await navigator.serviceWorker.controller.scriptURL : '';
9        if (scriptUrl.includes('OneSignalSDKWorker.js') && !scriptUrl.includes('push/onesignal')) {
10            var registrations = await navigator.serviceWorker.getRegistrations();
11            registrations.forEach( async (reg) => {
12                if (reg && reg.active && reg.active.scriptURL && reg.active.scriptURL === scriptUrl) {
13                    await reg.unregister();
14                }
15            })
16        } else {
17            var sw = '/sw.js';
18            if (pwaEnabled) {
19                sw = sw.indexOf('?') > -1 ? sw + '&pwa=true' : sw + '?pwa=true';
20            }
21            if (swCacheDisabled) {
22                sw = sw.indexOf('?') > -1 ? sw + '&sw-cache-dis=true' : sw + '?sw-cache-dis=true';
23            }
24            navigator.serviceWorker.register(sw).then(function (registration) {
25                console.log('ServiceWorker registration successful with scope: ', registration.scope);
26            }, function (err) {
27                console.log('ServiceWorker registration failed: ', err);
28            });
29        }
30    }
31});