service-worker.js

const CACHE_NAME = 'unserializeit-cache-v4';
const urlsToCache = [
	'/',
	'/index.html',
	'/assets/js/papaparse.js',
	'/assets/js/index.js',
];

self.addEventListener( 'install', ( event ) => {

	event.waitUntil(

		caches.open( CACHE_NAME ).then( ( cache ) => {

			return cache.addAll( urlsToCache );
		})
	);
});

self.addEventListener( 'fetch', ( event ) => {

	event.respondWith(

		caches.match( event.request ).then( ( response ) => {

			if ( response ) {
					return response;
			}

			return fetch( event.request );
		})
	);
});

self.addEventListener( 'activate', ( event ) => {

	const cacheWhitelist = [ CACHE_NAME ];

	event.waitUntil(

		caches.keys().then( ( cacheNames ) => {

			return Promise.all(

				cacheNames.map( ( cacheName ) => {

					if ( cacheWhitelist.indexOf( cacheName ) === -1 ) {

						return caches.delete( cacheName );
					}
				})
			);
		})
	);
});