Offline SW example

offline-swer.js

function getFilenameFromUrl(path){
    path = path.substring(path.lastIndexOf("/")+ 1);
    return (path.match(/[^.]+(\.[^?#]+)?/) || [])[0];
}

this.addEventListener('fetch', event => {

  if (event.request.mode === 'navigate' || (event.request.method === 'GET' && event.request.headers.get('accept').includes('text/html'))) {
        event.respondWith(
          fetch(event.request.url).catch(error => {
              var cachedFile = getFilenameFromUrl(event.request.url);
              // Return the offline page
              return caches.match(cachedFile);
          })
    );
  }
}