Cache: match() method

{{APIRef("Service Workers API")}}{{SecureContext_Header}}{{AvailableInWorkers}}

The match() method of the {{domxref("Cache")}} interface returns a {{jsxref("Promise")}} that resolves to the {{domxref("Response")}} associated with the first matching request in the {{domxref("Cache")}} object. If no match is found, the {{jsxref("Promise")}} resolves to {{jsxref("undefined")}}.

Syntax

match(request)
match(request, options)

Parameters

• request
  • : The {{domxref("Request")}} for which you are attempting to find responses in the {{domxref("Cache")}}. This can be a {{domxref("Request")}} object or a URL string.
• options {{optional_inline}}
  • : 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 of https://example.com/?value=bar would be ignored when performing a match. It defaults to false.
    • ignoreMethod
      • : A boolean value that, when set to true, prevents matching operations from validating the {{domxref("Request")}} http method (normally only GET and HEAD are allowed.) It defaults to false.
    • ignoreVary
      • : A boolean value that when set to true tells the matching operation not to perform VARY header matching — i.e., if the URL matches you will get a match regardless of whether the {{domxref("Response")}} object has a VARY header. It defaults to false.

Return value

A {{jsxref("Promise")}} that resolves to the first {{domxref("Response")}} that matches the request or to {{jsxref("undefined")}} if no match is found.

[!NOTE] Cache.match() is basically identical to {{domxref("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 a 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

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• Using Service Workers
• {{domxref("Cache")}}
• {{domxref("Window.caches")}} and {{domxref("WorkerGlobalScope.caches")}}