workbox()

nebula.workbox = async function(){
    jQuery('.nebula-sw-install-button').addClass('inactive'); //If manually placing this button, start with this inactive class to prevent CLS

    if ( nebula.site?.options?.sw ){ //If Service Worker is enabled in Nebula Options
        if ( 'serviceWorker' in navigator ){ //If Service Worker is supported (Firefox 44+, Chrome 45+, Edge 17+, Safari 12+)
            //When debugging unregister SW and clear caches
            if ( nebula.site?.options?.bypass_cache || nebula.get('debug') || nebula.get('audit') || nebula.dom.html.hasClass('debug') ){
                nebula.unregisterServiceWorker(); //Unregister the ServiceWorker
                nebula.emptyCaches(); //Clear the caches
                return false;
            }

            window.performance.mark('(Nebula) SW Registration [Start]');

            //Dynamically import Workbox-Window
            import('https://cdn.jsdelivr.net/npm/[email protected]/build/workbox-window.prod.mjs').then(function(module){
                const Workbox = module.Workbox;
                const workbox = new Workbox(nebula.site.sw_url);

                //Listen for Service Worker installation (this is different than PWA installation)
                workbox.addEventListener('installed', function(event){
                    //Skip waiting
                    workbox.messageSkipWaiting(); //Will probably end up using this, but try it without if first- it was not in the tutorial

                    if ( !event.isUpdate ){
                        //Service worker installed for the first time
                    }
                });

                //Activate the service worker
                workbox.addEventListener('activated', async function(event){
                    //Send the Workbox service worker router a list of resources to cache
                    workbox.messageSW({
                        type: 'CACHE_URLS', //This message type is handled in Workbox
                        payload: {
                            urlsToCache: [
                                location.href, //Current page
                                ...performance.getEntriesByType('resource').map(function(resource){ //Get all of the resources used by this page
                                    return resource.name;
                                }),
                            ]
                        },
                    });

                    //Now we can send messages back and forth
                    nebula.dom.document.trigger('nebula_workbox_active', workbox); //Allow others to interactive with Workbox (Ex: send messages with workbox.messageSW)
                    //const swVersion = await workbox.messageSW({type: 'GET_VERSION'}); //The message type here must match what the SW expects

                    //event.isUpdate will be true if another version of the service worker was controlling the page when this version was registered. It will be false on the very first installation
                    if ( !event.isUpdate ){
                        //If your service worker is configured to precache assets, those assets should all be available now.
                        nebula.dom.document.trigger('nebula_sw_first_activation');
                    }
                });

                //When the service worker begins controlling
                workbox.addEventListener('controlling', function(event){
                    //Service worker is now controlling
                });

                //Waiting to activate the new service worker until all tabs running the current version have fully unloaded
                workbox.addEventListener('waiting', function(event){
                    //A new service worker has installed, but it cannot activate until all tabs running the current version have fully unloaded.
                    //Create an update button to reload the page
                    jQuery('<button id="nebula-sw-update"><i class="fa-solid fa-sync-alt"></i> Update available. Click to reload.</button>').appendTo('body').on('click', function(){
                        window.location.reload();
                        nebula.animate('#nebula-sw-update', 'nebula-zoom-out');
                        return false;
                    });

                    //Show the button
                    //window.requestIdleCallback(function(){ //when Safari supports requestIdleCallback
                        window.requestAnimationFrame(function(){
                            //jQuery('#nebula-sw-update').addClass('active'); //Not showing to users as of Feb 2021. Need to make sure this reload method works (and with multiple tabs)
                        });
                    //});
                });

                //If the service worker becomes redundant
                workbox.addEventListener('redundant', function(event){
                    gtag('event', 'exception', {
                        message: '(JS) The installed service worker became redundant.',
                        fatal: false
                    });
                });

                //Notify the user of cache updates (this is from documentation, so test this thoroughly)
                workbox.addEventListener('message', function(event){
                    if ( event.data.type === 'CACHE_UPDATED' ){
                        const updatedURL = event.data.payload;
                    }

                    nebula.dom.document.trigger('nebula_sw_message', event.data);
                });

                //Register the service worker after above workbox event listeners have been added
                workbox.register().then(function(){
                    window.performance.mark('(Nebula) SW Registration [End]');
                    window.performance.measure('(Nebula) SW Registration', '(Nebula) SW Registration [Start]', '(Nebula) SW Registration [End]');
                }).catch(function(error){
                    gtag('event', 'exception', {
                        message: '(JS) ServiceWorker registration failed: ' + error,
                        fatal: false
                    });
                });
            });

            nebula.pwa();
        }
    } else {
        nebula.unregisterServiceWorker();
    }
};

For non-module import functions:

nebula.workbox = function(){
    //Write your own code here, leave it blank, or return false.
}

For dynamically imported module function overrides:

jQuery(window).on('load', function(){
    nebula.workbox = function(){
        //Write your own code here, leave it blank, or return false.
    }
});

Custom Nebula DOM events do also exist, so you could also try the following if the Window Load listener does not work:

jQuery(document).on('nebula_module_loaded', function(module){
    //Note that the module variable is also available to know which module specifically was imported
    if ( typeof nebula.workbox === 'function' ){
        nebula.workbox = function(){
            //Write your own code here, leave it blank, or return false.
        }
	}
});