FetchEvent.request

The request read-only property of the FetchEvent interface returns the Request that triggered the event handler.

This property is non-nullable (since version 46, in the case of Firefox.) If a request is not provided by some other means, the constructor init object must contain a request (see FetchEvent.FetchEvent().)

Syntax

var recentRequest = FetchEvent.request;

Value

A Request object.

Example

This code snippet is from the service worker fetch sample (run the fetch sample live). The ServiceWorkerGlobalScope.onfetch event handler listens for the fetch event. When fired, FetchEvent.respondWith(any value) returns a promise back to the controlled page. This promise resolves to the first matching URL request in the Cache object. If no match is found, the code fetches a response from the network.

The code also handles exceptions thrown from the ServiceWorkerGlobalScope.fetch operation. Note that an HTTP error response (e.g., 404) will not trigger an exception. It will return a normal response object that has the appropriate error code set.

self.addEventListener('fetch', function(event) {
  console.log('Handling fetch event for', event.request.url);

  event.respondWith(
    caches.match(event.request).then(function(response) {
      if (response) {
        console.log('Found response in cache:', response);

        return response;
      }
      console.log('No response found in cache. About to fetch from network...');

      return fetch(event.request).then(function(response) {
        console.log('Response from network is:', response);

        return response;
      }).catch(function(error) {
        console.error('Fetching failed:', error);

        throw error;
      });
    })
  );
});

Specifications

Specification	Status	Comment
Service Workers The definition of 'FetchEvent' in that specification.	Working Draft	Initial definition.

Browser compatibility

[1] Service workers (and Push) have been disabled in the Firefox 45 Extended Support Release (ESR.)

See also

• Using Service Workers
• Service workers basic code example
• Is ServiceWorker ready?
• Promise
• Using web workers