FetchEvent.request
This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.
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
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | 40.0 | 44.0 (44.0)[1] | No support | 24 | No support |
Feature | Android | Android Webview | Firefox Mobile (Gecko) | Firefox OS | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
---|---|---|---|---|---|---|---|---|
Basic support | No support | ? | 44.0 (44.0) | (Yes) | No support | ? | No support | 44.0 |
[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
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/api/fetchevent/request