sw.js

/* eslint-disable */
const HTMLToCache = '/';
const version = 'MSW V0.3';

self.addEventListener('install', event => {
  event.waitUntil(
    caches.open(version).then(cache => {
      cache.add(HTMLToCache).then(self.skipWaiting());
    })
  );
});

self.addEventListener('activate', event => {
  event.waitUntil(
    caches
      .keys()
      .then(cacheNames =>
        Promise.all(
          cacheNames.map(cacheName => {
            if (version !== cacheName) return caches.delete(cacheName);
          })
        )
      )
      .then(self.clients.claim())
  );
});

self.addEventListener('fetch', event => {
  const requestToFetch = event.request.clone();
  event.respondWith(
    caches.match(event.request.clone()).then(cached => {
      // We don't return cached HTML (except if fetch failed)
      if (cached) {
        const resourceType = cached.headers.get('content-type');
        // We only return non css/js/html cached response e.g images
        if (!hasHash(event.request.url) && !/text\/html/.test(resourceType)) {
          return cached;
        }

        // If the CSS/JS didn't change since it's been cached, return the cached version
        if (
          hasHash(event.request.url) &&
          hasSameHash(event.request.url, cached.url)
        ) {
          return cached;
        }
      }
      return fetch(requestToFetch)
        .then(response => {
          const clonedResponse = response.clone();
          const contentType = clonedResponse.headers.get('content-type');

          if (
            !clonedResponse ||
            clonedResponse.status !== 200 ||
            clonedResponse.type !== 'basic' ||
            /\/sockjs\//.test(event.request.url)
          ) {
            return response;
          }

          if (/html/.test(contentType)) {
            caches
              .open(version)
              .then(cache => cache.put(HTMLToCache, clonedResponse));
          } else {
            // Delete old version of a file
            if (hasHash(event.request.url)) {
              caches.open(version).then(cache =>
                cache.keys().then(keys =>
                  keys.forEach(asset => {
                    if (
                      new RegExp(removeHash(event.request.url)).test(
                        removeHash(asset.url)
                      )
                    ) {
                      cache.delete(asset);
                    }
                  })
                )
              );
            }

            caches
              .open(version)
              .then(cache => cache.put(event.request, clonedResponse));
          }
          return response;
        })
        .catch(() => {
          if (hasHash(event.request.url))
            return caches.match(event.request.url);
          else if (!/\/sockjs\//.test(event.request.url))
            // If the request URL hasn't been served from cache and isn't sockjs we suppose it's HTML
            return caches.match(HTMLToCache);
          // Only for sockjs
          return new Response('No connection to the server', {
            status: 503,
            statusText: 'No connection to the server',
            headers: new Headers({ 'Content-Type': 'text/plain' }),
          });
        });
    })
  );
});

function removeHash(element) {
  if (typeof element === 'string') return element.split('?hash=')[0];
}

function hasHash(element) {
  if (typeof element === 'string') return /\?hash=.*/.test(element);
}

function hasSameHash(firstUrl, secondUrl) {
  if (typeof firstUrl === 'string' && typeof secondUrl === 'string') {
    return /\?hash=(.*)/.exec(firstUrl)[1] === /\?hash=(.*)/.exec(secondUrl)[1];
  }
}

// Service worker created by Ilan Schemoul alias NitroBAY as a specific Service Worker for Meteor
// Please see https://github.com/NitroBAY/meteor-service-worker for the official project source