I keep getting this error in the console log

Uncaught (in promise) TypeError: Failed to execute 'fetch' on 'ServiceWorkerGlobalScope': Cannot construct a Request with a Request object that has already been used.

I tried changing my service worker but it doesn't work

self.addEventListener('install', (event) => event.waitUntil(preLoad()));

const preLoad = function () {
  return caches.open('cc-offline').then((cache) => {
    return cache.addAll(['/offline.html', '/index.html']);
  });
}

self.addEventListener('fetch', (event) => {
  event.respondWith(checkResponse(event.request).catch(function () {
    return returnFromCache(event.request)
  }));
  event.waitUntil(addToCache(event.request));
});

const checkResponse = (request) => {
  return new Promise((fulfill, reject) => {
    fetch(request).then((response) => {
      (response.status !== 404) ? fulfill(response) : reject()
    }, reject)
  });
};

const addToCache = (request) => {
  return caches.open('cc-offline').then((cache) => {
    return fetch(request).then((response) => {
      return cache.put(request, response);
    });
  });
};

const returnFromCache = (request) => {
  return caches.open('cc-offline').then((cache) => {
    return cache.match(request).then((matching) => {
      return (!matching || matching.status == 404) ? cache.match('offline.html') : matching
    });
  });
};

I keep getting this error in the console log

Uncaught (in promise) TypeError: Failed to execute 'fetch' on 'ServiceWorkerGlobalScope': Cannot construct a Request with a Request object that has already been used.

I tried changing my service worker but it doesn't work

self.addEventListener('install', (event) => event.waitUntil(preLoad()));

const preLoad = function () {
  return caches.open('cc-offline').then((cache) => {
    return cache.addAll(['/offline.html', '/index.html']);
  });
}

self.addEventListener('fetch', (event) => {
  event.respondWith(checkResponse(event.request).catch(function () {
    return returnFromCache(event.request)
  }));
  event.waitUntil(addToCache(event.request));
});

const checkResponse = (request) => {
  return new Promise((fulfill, reject) => {
    fetch(request).then((response) => {
      (response.status !== 404) ? fulfill(response) : reject()
    }, reject)
  });
};

const addToCache = (request) => {
  return caches.open('cc-offline').then((cache) => {
    return fetch(request).then((response) => {
      return cache.put(request, response);
    });
  });
};

const returnFromCache = (request) => {
  return caches.open('cc-offline').then((cache) => {
    return cache.match(request).then((matching) => {
      return (!matching || matching.status == 404) ? cache.match('offline.html') : matching
    });
  });
};

• javascript
• node.js
• vue.js
• service-worker

1 Answer 1

fetch don't allow you to use a request twice, at least at current version :). Using the same request object in both checkResponse and addToCache maybe the case. You can try to clone the request object before calling fetch as mention in here Why does this code fail to execute 'fetch'?