When service workers were first introduced, a set of common caching strategies emerged. A caching strategy is a pattern that determines how a service worker generates a response after receiving a fetch event.
workbox-strategies
provides the most common caching strategies so it's easy to
apply them in your service worker.
We won't go into much detail outside of the strategies supported by Workbox, but you can learn more in the Offline Cookbook.
Using Strategies
In the following examples, we'll show you how to use the Workbox caching
strategies with workbox-routing
. There are some options you can define with
each strategy that are covered in the
Configuring Strategies section of this doc.
In the Advanced Usage section, we'll cover how you can use
the caching strategies directly without workbox-routing
.
Stale-While-Revalidate
The stale-while-revalidate pattern allows you to respond to the request as quickly as possible with a cached response if available, falling back to the network request if it's not cached. The network request is then used to update the cache. As opposed to some implementations of stale-while-revalidate, this strategy will always make a revalidation request, regardless of the age of the cached response.
This is a fairly common strategy where having the most up-to-date resource is not vital to the application.
import {registerRoute} from 'workbox-routing';
import {StaleWhileRevalidate} from 'workbox-strategies';
registerRoute(
({url}) => url.pathname.startsWith('/images/avatars/'),
new StaleWhileRevalidate()
);
Cache First (Cache Falling Back to Network)
Offline web apps will rely heavily on the cache, but for assets that are non-critical and can be gradually cached, a cache first is the best option.
If there is a Response in the cache, the Request will be fulfilled using the cached response and the network will not be used at all. If there isn't a cached response, the Request will be fulfilled by a network request and the response will be cached so that the next request is served directly from the cache.
import {registerRoute} from 'workbox-routing';
import {CacheFirst} from 'workbox-strategies';
registerRoute(({request}) => request.destination === 'style', new CacheFirst());
Network First (Network Falling Back to Cache)
For requests that are updating frequently, the network first strategy is the ideal solution. By default, it will try to fetch the latest response from the network. If the request is successful, it'll put the response in the cache. If the network fails to return a response, the cached response will be used.
import {registerRoute} from 'workbox-routing';
import {NetworkFirst} from 'workbox-strategies';
registerRoute(
({url}) => url.pathname.startsWith('/social-timeline/'),
new NetworkFirst()
);
Network Only
If you require specific requests to be fulfilled from the network, the network only is the strategy to use.
import {registerRoute} from 'workbox-routing';
import {NetworkOnly} from 'workbox-strategies';
registerRoute(({url}) => url.pathname.startsWith('/admin/'), new NetworkOnly());
Cache Only
The cache only strategy ensures that responses are obtained from a cache. This is less common in workbox, but can be useful if you have your own precaching step.
import {registerRoute} from 'workbox-routing';
import {CacheOnly} from 'workbox-strategies';
registerRoute(({url}) => url.pathname.startsWith('/app/v2/'), new CacheOnly());
Configuring Strategies
All of the strategies allow you to configure:
- The name of the cache to use in the strategy.
- Cache expiration restrictions to use in the strategy.
- An array of plugins that will have their lifecycle methods called when fetching and caching a request.
Changing the Cache Used by a Strategy
You can change the cache a strategy used by supplying a cache name. This is useful if you want to separate out your assets to help with debugging.
import {registerRoute} from 'workbox-routing';
import {CacheFirst} from 'workbox-strategies';
registerRoute(
({request}) => request.destination === 'image',
new CacheFirst({
cacheName: 'image-cache',
})
);
Using Plugins
Workbox comes with a set of plugins that can be used with these strategies.
- workbox-background-sync
- workbox-broadcast-update
- workbox-cacheable-response
- workbox-expiration
- workbox-range-requests
To use any of these plugins (or a custom plugin), you just need to pass in
instances to the plugins
option.
import {registerRoute} from 'workbox-routing';
import {CacheFirst} from 'workbox-strategies';
import {ExpirationPlugin} from 'workbox-expiration';
registerRoute(
({request}) => request.destination === 'image',
new CacheFirst({
cacheName: 'image-cache',
plugins: [
new ExpirationPlugin({
// Only cache requests for a week
maxAgeSeconds: 7 * 24 * 60 * 60,
// Only cache 10 requests.
maxEntries: 10,
}),
],
})
);
Custom Strategies
In addition to configuring strategies, Workbox allows you to create your own custom strategies.
This can be done by importing and extending the Strategy
base class from workbox-strategies
:
import {Strategy} from 'workbox-strategies';
class NewStrategy extends Strategy {
_handle(request, handler) {
// Define handling logic here
}
}
In this example, handle()
is used as a request strategy to define specific handling logic. There
are two request strategies that can be used:
handle()
: Perform a request strategy and return aPromise
that will resolve with aResponse
, invoking all relevant plugin callbacks.handleAll()
: Similar tohandle()
, but returns twoPromise
objects. The first is equivalent to whathandle()
returns and the second will resolve when promises that were added toevent.waitUntil()
within the strategy have completed.
Both request strategies are invoked with two parameters:
request
: TheRequest
the strategy will return a response for.handler
: AStrategyHandler
instance automatically created for the current strategy.
Creating A New Strategy
The following is an example of a new strategy that re-implements the behavior of NetworkOnly
:
class NewNetworkOnlyStrategy extends Strategy {
_handle(request, handler) {
return handler.fetch(request);
}
}
Notice how handler.fetch()
is called instead of the native fetch
method. The StrategyHandler
class provides a number of fetch and cache actions that can be used whenever handle()
or
handleAll()
is used:
fetch
: Fetches a given request, and invokes therequestWillFetch()
,fetchDidSucceed()
, andfetchDidFail()
plugin lifecycle methodscacheMatch
: Matches a request from the cache, and invokes thecacheKeyWillBeUsed()
andcachedResponseWillBeUsed()
plugin lifecycle methodscachePut
: Puts a request/response pair in the cache, and invokes thecacheKeyWillBeUsed()
,cacheWillUpdate()
, andcacheDidUpdate()
plugin lifecycle methodsfetchAndCachePut
: Callsfetch()
and runscachePut()
in the background on the response generated byfetch()
.hasCallback
: Takes a callback as input and returns true if the strategy has at least one plugin with the given callback.runCallbacks
: Runs all plugin callbacks matching a given name, in order, passing a given param object (merged with the current plugin state) as the only argument.iterateCallbacks
: Accepts a callback and returns an iterable of matching plugin callbacks, where each callback is wrapped with the current handler state (i.e. when you call each callback, whatever object parameter you pass it will be merged with the plugin's current state).waitUntil
: Adds a promise to the extend lifetime promises of the event associated with the request being handled (usually aFetchEvent
).doneWaiting
: Returns a promise that resolves once all promises passed towaitUntil()
have settled.destroy
: Stops running the strategy and immediately resolves any pendingwaitUntil()
promises.
Custom Cache Network Race Strategy
The following example is based on cache-network-race from the Offline Cookbook (which Workbox does not provide), but goes a step further and always updates the cache after a successful network request. This in an example of a more complex strategy that uses multiple actions.
import {Strategy} from 'workbox-strategies';
class CacheNetworkRace extends Strategy {
_handle(request, handler) {
const fetchAndCachePutDone = handler.fetchAndCachePut(request);
const cacheMatchDone = handler.cacheMatch(request);
return new Promise((resolve, reject) => {
fetchAndCachePutDone.then(resolve);
cacheMatchDone.then(response => response && resolve(response));
// Reject if both network and cache error or find no response.
Promise.allSettled([fetchAndCachePutDone, cacheMatchDone]).then(
results => {
const [fetchAndCachePutResult, cacheMatchResult] = results;
if (
fetchAndCachePutResult.status === 'rejected' &&
!cacheMatchResult.value
) {
reject(fetchAndCachePutResult.reason);
}
}
);
});
}
}
Advanced Usage
If you want to use the strategies in your own fetch event logic, you can use the strategy classes to run a request through a specific strategy.
For example, to use the stale-while-revalidate strategy, you can do the following:
self.addEventListener('fetch', event => {
const {request} = event;
const url = new URL(request.url);
if (url.origin === location.origin && url.pathname === '/') {
event.respondWith(new StaleWhileRevalidate().handle({event, request}));
}
});
You can find the list of available classes in the workbox-strategies reference docs.
Types
CacheFirst
An implementation of a cache-first request strategy.
A cache first strategy is useful for assets that have been revisioned,
such as URLs like /styles/example.a8f5f1.css
, since they
can be cached for long periods of time.
If the network request fails, and there is no cache match, this will throw
a WorkboxError
exception.
Properties
-
constructor
void
Creates a new instance of the strategy and sets all documented option properties as public instance properties.
Note: if a custom strategy class extends the base Strategy class and does not need more than these properties, it does not need to define its own constructor.
The
constructor
function looks like:(options?: StrategyOptions) => {...}
-
options
StrategyOptions optional
-
returns
-
-
cacheName
string
-
fetchOptions
RequestInit optional
-
matchOptions
CacheQueryOptions optional
-
plugins
-
_awaitComplete
void
The
_awaitComplete
function looks like:(responseDone: Promise<Response>, handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
responseDone
Promise<Response>
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<void>
-
-
_getResponse
void
The
_getResponse
function looks like:(handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<Response>
-
-
handle
void
Perform a request strategy and returns a
Promise
that will resolve with aResponse
, invoking all relevant plugin callbacks.When a strategy instance is registered with a Workbox
workbox-routing.Route
, this method is automatically called when the route matches.Alternatively, this method can be used in a standalone
FetchEvent
listener by passing it toevent.respondWith()
.The
handle
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
Promise<Response>
-
-
handleAll
void
Similar to
workbox-strategies.Strategy~handle
, but instead of just returning aPromise
that resolves to aResponse
it it will return an tuple of[response, done]
promises, where the former (response
) is equivalent to whathandle()
returns, and the latter is a Promise that will resolve once any promises that were added toevent.waitUntil()
as part of performing the strategy have completed.You can await the
done
promise to ensure any extra work performed by the strategy (usually caching responses) completes successfully.The
handleAll
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
[Promise<Response>, Promise<void>]
A tuple of [response, done] promises that can be used to determine when the response resolves as well as when the handler has completed all its work.
-
CacheOnly
An implementation of a cache-only request strategy.
This class is useful if you want to take advantage of any Workbox plugins.
If there is no cache match, this will throw a WorkboxError
exception.
Properties
-
constructor
void
Creates a new instance of the strategy and sets all documented option properties as public instance properties.
Note: if a custom strategy class extends the base Strategy class and does not need more than these properties, it does not need to define its own constructor.
The
constructor
function looks like:(options?: StrategyOptions) => {...}
-
options
StrategyOptions optional
-
returns
-
-
cacheName
string
-
fetchOptions
RequestInit optional
-
matchOptions
CacheQueryOptions optional
-
plugins
-
_awaitComplete
void
The
_awaitComplete
function looks like:(responseDone: Promise<Response>, handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
responseDone
Promise<Response>
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<void>
-
-
_getResponse
void
The
_getResponse
function looks like:(handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<Response>
-
-
handle
void
Perform a request strategy and returns a
Promise
that will resolve with aResponse
, invoking all relevant plugin callbacks.When a strategy instance is registered with a Workbox
workbox-routing.Route
, this method is automatically called when the route matches.Alternatively, this method can be used in a standalone
FetchEvent
listener by passing it toevent.respondWith()
.The
handle
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
Promise<Response>
-
-
handleAll
void
Similar to
workbox-strategies.Strategy~handle
, but instead of just returning aPromise
that resolves to aResponse
it it will return an tuple of[response, done]
promises, where the former (response
) is equivalent to whathandle()
returns, and the latter is a Promise that will resolve once any promises that were added toevent.waitUntil()
as part of performing the strategy have completed.You can await the
done
promise to ensure any extra work performed by the strategy (usually caching responses) completes successfully.The
handleAll
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
[Promise<Response>, Promise<void>]
A tuple of [response, done] promises that can be used to determine when the response resolves as well as when the handler has completed all its work.
-
NetworkFirst
An implementation of a network first request strategy.
By default, this strategy will cache responses with a 200 status code as well as opaque responses. Opaque responses are are cross-origin requests where the response doesn't support CORS.
If the network request fails, and there is no cache match, this will throw
a WorkboxError
exception.
Properties
-
constructor
void
The
constructor
function looks like:(options?: NetworkFirstOptions) => {...}
-
options
NetworkFirstOptions optional
-
returns
-
-
cacheName
string
-
fetchOptions
RequestInit optional
-
matchOptions
CacheQueryOptions optional
-
plugins
-
_awaitComplete
void
The
_awaitComplete
function looks like:(responseDone: Promise<Response>, handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
responseDone
Promise<Response>
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<void>
-
-
_getResponse
void
The
_getResponse
function looks like:(handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<Response>
-
-
handle
void
Perform a request strategy and returns a
Promise
that will resolve with aResponse
, invoking all relevant plugin callbacks.When a strategy instance is registered with a Workbox
workbox-routing.Route
, this method is automatically called when the route matches.Alternatively, this method can be used in a standalone
FetchEvent
listener by passing it toevent.respondWith()
.The
handle
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
Promise<Response>
-
-
handleAll
void
Similar to
workbox-strategies.Strategy~handle
, but instead of just returning aPromise
that resolves to aResponse
it it will return an tuple of[response, done]
promises, where the former (response
) is equivalent to whathandle()
returns, and the latter is a Promise that will resolve once any promises that were added toevent.waitUntil()
as part of performing the strategy have completed.You can await the
done
promise to ensure any extra work performed by the strategy (usually caching responses) completes successfully.The
handleAll
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
[Promise<Response>, Promise<void>]
A tuple of [response, done] promises that can be used to determine when the response resolves as well as when the handler has completed all its work.
-
NetworkFirstOptions
Properties
-
cacheName
string optional
-
fetchOptions
RequestInit optional
-
matchOptions
CacheQueryOptions optional
-
networkTimeoutSeconds
number optional
-
plugins
WorkboxPlugin[] optional
NetworkOnly
An implementation of a network-only request strategy.
This class is useful if you want to take advantage of any Workbox plugins.
If the network request fails, this will throw a WorkboxError
exception.
Properties
-
constructor
void
The
constructor
function looks like:(options?: NetworkOnlyOptions) => {...}
-
options
NetworkOnlyOptions optional
-
returns
-
-
cacheName
string
-
fetchOptions
RequestInit optional
-
matchOptions
CacheQueryOptions optional
-
plugins
-
_awaitComplete
void
The
_awaitComplete
function looks like:(responseDone: Promise<Response>, handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
responseDone
Promise<Response>
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<void>
-
-
_getResponse
void
The
_getResponse
function looks like:(handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<Response>
-
-
handle
void
Perform a request strategy and returns a
Promise
that will resolve with aResponse
, invoking all relevant plugin callbacks.When a strategy instance is registered with a Workbox
workbox-routing.Route
, this method is automatically called when the route matches.Alternatively, this method can be used in a standalone
FetchEvent
listener by passing it toevent.respondWith()
.The
handle
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
Promise<Response>
-
-
handleAll
void
Similar to
workbox-strategies.Strategy~handle
, but instead of just returning aPromise
that resolves to aResponse
it it will return an tuple of[response, done]
promises, where the former (response
) is equivalent to whathandle()
returns, and the latter is a Promise that will resolve once any promises that were added toevent.waitUntil()
as part of performing the strategy have completed.You can await the
done
promise to ensure any extra work performed by the strategy (usually caching responses) completes successfully.The
handleAll
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
[Promise<Response>, Promise<void>]
A tuple of [response, done] promises that can be used to determine when the response resolves as well as when the handler has completed all its work.
-
NetworkOnlyOptions
Properties
-
fetchOptions
RequestInit optional
-
networkTimeoutSeconds
number optional
-
plugins
WorkboxPlugin[] optional
StaleWhileRevalidate
An implementation of a stale-while-revalidate request strategy.
Resources are requested from both the cache and the network in parallel. The strategy will respond with the cached version if available, otherwise wait for the network response. The cache is updated with the network response with each successful request.
By default, this strategy will cache responses with a 200 status code as well as opaque responses. Opaque responses are cross-origin requests where the response doesn't support CORS.
If the network request fails, and there is no cache match, this will throw
a WorkboxError
exception.
Properties
-
constructor
void
The
constructor
function looks like:(options?: StrategyOptions) => {...}
-
options
StrategyOptions optional
-
returns
-
-
cacheName
string
-
fetchOptions
RequestInit optional
-
matchOptions
CacheQueryOptions optional
-
plugins
-
_awaitComplete
void
The
_awaitComplete
function looks like:(responseDone: Promise<Response>, handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
responseDone
Promise<Response>
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<void>
-
-
_getResponse
void
The
_getResponse
function looks like:(handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<Response>
-
-
handle
void
Perform a request strategy and returns a
Promise
that will resolve with aResponse
, invoking all relevant plugin callbacks.When a strategy instance is registered with a Workbox
workbox-routing.Route
, this method is automatically called when the route matches.Alternatively, this method can be used in a standalone
FetchEvent
listener by passing it toevent.respondWith()
.The
handle
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
Promise<Response>
-
-
handleAll
void
Similar to
workbox-strategies.Strategy~handle
, but instead of just returning aPromise
that resolves to aResponse
it it will return an tuple of[response, done]
promises, where the former (response
) is equivalent to whathandle()
returns, and the latter is a Promise that will resolve once any promises that were added toevent.waitUntil()
as part of performing the strategy have completed.You can await the
done
promise to ensure any extra work performed by the strategy (usually caching responses) completes successfully.The
handleAll
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
[Promise<Response>, Promise<void>]
A tuple of [response, done] promises that can be used to determine when the response resolves as well as when the handler has completed all its work.
-
Strategy
An abstract base class that all other strategy classes must extend from:
Properties
-
constructor
void
Creates a new instance of the strategy and sets all documented option properties as public instance properties.
Note: if a custom strategy class extends the base Strategy class and does not need more than these properties, it does not need to define its own constructor.
The
constructor
function looks like:(options?: StrategyOptions) => {...}
-
options
StrategyOptions optional
-
returns
-
-
cacheName
string
-
fetchOptions
RequestInit optional
-
matchOptions
CacheQueryOptions optional
-
plugins
-
_awaitComplete
void
The
_awaitComplete
function looks like:(responseDone: Promise<Response>, handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
responseDone
Promise<Response>
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<void>
-
-
_getResponse
void
The
_getResponse
function looks like:(handler: StrategyHandler, request: Request, event: ExtendableEvent) => {...}
-
handler
-
request
Request
-
event
ExtendableEvent
-
returns
Promise<Response>
-
-
_handle
void
The
_handle
function looks like:(request: Request, handler: StrategyHandler) => {...}
-
request
Request
-
handler
-
returns
Promise<Response>
-
-
handle
void
Perform a request strategy and returns a
Promise
that will resolve with aResponse
, invoking all relevant plugin callbacks.When a strategy instance is registered with a Workbox
workbox-routing.Route
, this method is automatically called when the route matches.Alternatively, this method can be used in a standalone
FetchEvent
listener by passing it toevent.respondWith()
.The
handle
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
Promise<Response>
-
-
handleAll
void
Similar to
workbox-strategies.Strategy~handle
, but instead of just returning aPromise
that resolves to aResponse
it it will return an tuple of[response, done]
promises, where the former (response
) is equivalent to whathandle()
returns, and the latter is a Promise that will resolve once any promises that were added toevent.waitUntil()
as part of performing the strategy have completed.You can await the
done
promise to ensure any extra work performed by the strategy (usually caching responses) completes successfully.The
handleAll
function looks like:(options: FetchEvent | HandlerCallbackOptions) => {...}
-
options
FetchEvent | HandlerCallbackOptions
A
FetchEvent
or an object with the properties listed below.
-
returns
[Promise<Response>, Promise<void>]
A tuple of [response, done] promises that can be used to determine when the response resolves as well as when the handler has completed all its work.
-
StrategyHandler
A class created every time a Strategy instance instance calls
workbox-strategies.Strategy~handle
or
workbox-strategies.Strategy~handleAll
that wraps all fetch and
cache actions around plugin callbacks and keeps track of when the strategy
is "done" (i.e. all added event.waitUntil()
promises have resolved).
Properties
-
constructor
void
Creates a new instance associated with the passed strategy and event that's handling the request.
The constructor also initializes the state that will be passed to each of the plugins handling this request.
The
constructor
function looks like:(strategy: Strategy, options: HandlerCallbackOptions) => {...}
-
strategy
-
options
-
returns
-
-
event
ExtendableEvent
-
params
any optional
-
request
Request
-
url
URL optional
-
cacheMatch
void
Matches a request from the cache (and invokes any applicable plugin callback methods) using the
cacheName
,matchOptions
, andplugins
defined on the strategy object.The following plugin lifecycle methods are invoked when using this method:
- cacheKeyWillByUsed()
- cachedResponseWillByUsed()
The
cacheMatch
function looks like:(key: RequestInfo) => {...}
-
key
RequestInfo
The Request or URL to use as the cache key.
-
returns
Promise<Response>
A matching response, if found.
-
cachePut
void
Puts a request/response pair in the cache (and invokes any applicable plugin callback methods) using the
cacheName
andplugins
defined on the strategy object.The following plugin lifecycle methods are invoked when using this method:
- cacheKeyWillByUsed()
- cacheWillUpdate()
- cacheDidUpdate()
The
cachePut
function looks like:(key: RequestInfo, response: Response) => {...}
-
key
RequestInfo
The request or URL to use as the cache key.
-
response
Response
The response to cache.
-
returns
Promise<boolean>
false
if a cacheWillUpdate caused the response not be cached, andtrue
otherwise.
-
destroy
void
Stops running the strategy and immediately resolves any pending
waitUntil()
promises.The
destroy
function looks like:() => {...}
-
doneWaiting
void
Returns a promise that resolves once all promises passed to
workbox-strategies.StrategyHandler~waitUntil
have settled.Note: any work done after
doneWaiting()
settles should be manually passed to an event'swaitUntil()
method (not this handler'swaitUntil()
method), otherwise the service worker thread my be killed prior to your work completing.The
doneWaiting
function looks like:() => {...}
-
returns
Promise<void>
-
-
fetch
void
Fetches a given request (and invokes any applicable plugin callback methods) using the
fetchOptions
(for non-navigation requests) andplugins
defined on theStrategy
object.The following plugin lifecycle methods are invoked when using this method:
requestWillFetch()
fetchDidSucceed()
fetchDidFail()
The
fetch
function looks like:(input: RequestInfo) => {...}
-
input
RequestInfo
The URL or request to fetch.
-
returns
Promise<Response>
-
fetchAndCachePut
void
Calls
this.fetch()
and (in the background) runsthis.cachePut()
on the response generated bythis.fetch()
.The call to
this.cachePut()
automatically invokesthis.waitUntil()
, so you do not have to manually callwaitUntil()
on the event.The
fetchAndCachePut
function looks like:(input: RequestInfo) => {...}
-
input
RequestInfo
The request or URL to fetch and cache.
-
returns
Promise<Response>
-
-
getCacheKey
void
Checks the list of plugins for the
cacheKeyWillBeUsed
callback, and executes any of those callbacks found in sequence. The finalRequest
object returned by the last plugin is treated as the cache key for cache reads and/or writes. If nocacheKeyWillBeUsed
plugin callbacks have been registered, the passed request is returned unmodifiedThe
getCacheKey
function looks like:(request: Request, mode: "read"
| "write"
) => {...}-
request
Request
-
mode
"read"
| "write"
-
returns
Promise<Request>
-
-
hasCallback
void
Returns true if the strategy has at least one plugin with the given callback.
The
hasCallback
function looks like:(name: C) => {...}
-
name
C
The name of the callback to check for.
-
returns
boolean
-
-
iterateCallbacks
void
Accepts a callback and returns an iterable of matching plugin callbacks, where each callback is wrapped with the current handler state (i.e. when you call each callback, whatever object parameter you pass it will be merged with the plugin's current state).
The
iterateCallbacks
function looks like:(name: C) => {...}
-
name
C
The name fo the callback to run
-
returns
Generator<NonNullable<indexedAccess>anyunknown>
-
-
runCallbacks
void
Runs all plugin callbacks matching the given name, in order, passing the given param object (merged ith the current plugin state) as the only argument.
Note: since this method runs all plugins, it's not suitable for cases where the return value of a callback needs to be applied prior to calling the next callback. See
workbox-strategies.StrategyHandler#iterateCallbacks
below for how to handle that case.The
runCallbacks
function looks like:(name: C, param: Omit<indexedAccess"state"
>) => {...}-
name
C
The name of the callback to run within each plugin.
-
param
Omit<indexedAccess"state"
>The object to pass as the first (and only) param when executing each callback. This object will be merged with the current plugin state prior to callback execution.
-
returns
Promise<void>
-
-
waitUntil
void
Adds a promise to the [extend lifetime promises]
https://w3c.github.io/ServiceWorker/#extendableevent-extend-lifetime-promises
of the event event associated with the request being handled (usually aFetchEvent
).Note: you can await
workbox-strategies.StrategyHandler~doneWaiting
to know when all added promises have settled.The
waitUntil
function looks like:(promise: Promise<T>) => {...}
-
promise
Promise<T>
A promise to add to the extend lifetime promises of the event that triggered the request.
-
returns
Promise<T>
-
StrategyOptions
Properties
-
cacheName
string optional
-
fetchOptions
RequestInit optional
-
matchOptions
CacheQueryOptions optional
-
plugins
WorkboxPlugin[] optional