Baseline Widely available
Note: This feature is only available in Service Workers.
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 options object must contain a request (see FetchEvent().)
A Request object.
This code snippet is from the service worker fetch sample (run the fetch sample live). The onfetch event handler listens for the fetch event. When fired, pass a promise that back to the controlled page to FetchEvent.respondWith(). 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 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", (event) => {
console.log("Handling fetch event for", event.request.url);
event.respondWith(
caches.match(event.request).then((response) => {
if (response) {
console.log("Found response in cache:", response);
return response;
}
console.log("No response found in cache. About to fetch from networkâ¦");
return fetch(event.request)
.then((response) => {
console.log("Response from network is:", response);
return response;
})
.catch((error) => {
console.error("Fetching failed:", error);
throw error;
});
}),
);
});
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