Cache: match() method
Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
Note: This feature is available in Web Workers.
The match()
method of the Cache
interface returns a Promise
that resolves to the Response
associated with the first matching request in the Cache
object.
If no match is found, the Promise
resolves to undefined
.
Syntax
match(request)
match(request, options)
Parameters
request
-
The
Request
for which you are attempting to find responses in theCache
. This can be aRequest
object or a URL string. options
Optional-
An object that sets options for the
match
operation. The available options are:ignoreSearch
-
A boolean value that specifies whether to ignore the query string in the URL. For example, if set to
true
the?value=bar
part ofhttp://foo.com/?value=bar
would be ignored when performing a match. It defaults tofalse
. ignoreMethod
-
A boolean value that, when set to
true
, prevents matching operations from validating theRequest
http
method (normally onlyGET
andHEAD
are allowed.) It defaults tofalse
. ignoreVary
-
A boolean value that when set to
true
tells the matching operation not to performVARY
header matching — i.e. if the URL matches you will get a match regardless of whether theResponse
object has aVARY
header. It defaults tofalse
.
Return value
A Promise
that resolves to the first Response
that matches
the request or to undefined
if no match is found.
Note: Cache.match()
is basically identical to
Cache.matchAll()
, except that rather than resolving with an array of
all matching responses, it resolves with the first matching response only (that is,
response[0]
).
Examples
This example is taken from the custom offline page example (live demo). It uses a cache to supply selected data when a request fails. A
catch()
clause is triggered when the call to fetch()
throws an
exception. Inside the catch()
clause, match()
is used to
return the correct response.
In this example, only HTML documents retrieved with the GET HTTP verb will be
cached. If our if ()
condition is false, then this fetch handler won't
intercept the request. If there are any other fetch handlers registered, they will get a
chance to call event.respondWith()
. If no fetch handlers call
event.respondWith()
, the request will be handled by the browser as if there
were no service worker involvement. If fetch()
returns a valid HTTP
response with an response code in the 4xx or 5xx range, the catch()
will
NOT be called.
self.addEventListener("fetch", (event) => {
// We only want to call event.respondWith() if this is a GET request for an HTML document.
if (
event.request.method === "GET" &&
event.request.headers.get("accept").includes("text/html")
) {
console.log("Handling fetch event for", event.request.url);
event.respondWith(
fetch(event.request).catch((e) => {
console.error("Fetch failed; returning offline page instead.", e);
return caches
.open(OFFLINE_CACHE)
.then((cache) => cache.match(OFFLINE_URL));
}),
);
}
});
Specifications
Specification |
---|
Service Workers # cache-match |
Browser compatibility
BCD tables only load in the browser