The ExtendableEvent.waitUntil()
method tells the event dispatcher that work is ongoing. It can also be used to detect whether that work was successful. In service workers, waitUntil()
tells the browser that work is ongoing until the promise settles, and it shouldn't terminate the service worker if it wants that work to complete.
The install
events in service workers
use waitUntil()
to hold the service worker in the installing
phase until tasks complete. If the promise passed to waitUntil()
rejects, the install is considered a failure, and the installing service worker is discarded. This is primarily used to ensure that a service worker is not considered installed until all of the core caches it depends on are successfully populated.
The activate
events in service workers
use waitUntil()
to buffer functional events such as fetch
and push
until the promise passed to waitUntil()
settles. This gives the service worker time to update database schemas and delete outdated caches
, so other events can rely on a completely upgraded state.
The waitUntil()
method must be initially called within the event callback, but after that it can be called multiple times, until all the promises passed to it settle.
Note: The behaviour described in the above paragraph was fixed in Firefox 43 (see bug 1180274).
Syntax
extendableEvent.waitUntil(promise);
Parameters
A Promise
.
Return value
undefined
.
Example
Using waitUntil()
within a service worker's install
event:
addEventListener('install', event => { const preCache = async () => { const cache = await caches.open('static-v1'); return cache.addAll([ '/', '/about/', '/static/styles.css' ]); }; event.waitUntil(preCache()); });
Specifications
Specification | Status | Comment |
---|---|---|
Service Workers The definition of 'waitUntil()' in that specification. |
Working Draft | Initial definition |
Browser compatibility
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
waitUntil | Chrome Full support 40 | Edge Full support 17 | Firefox Full support 44 | IE No support No | Opera Full support 24 | Safari No support No | WebView Android Full support 40 | Chrome Android Full support 40 | Firefox Android Full support 44 | Opera Android Full support 24 | Safari iOS No support No | Samsung Internet Android Full support 4.0 |
Asynchronous waitUntil | Chrome ? | Edge Full support 17 | Firefox Full support 53 | IE No support No | Opera ? | Safari No support No | WebView Android ? | Chrome Android ? | Firefox Android Full support 53 | Opera Android ? | Safari iOS No support No | Samsung Internet Android ? |
Legend
- Full support
- Full support
- No support
- No support
- Compatibility unknown
- Compatibility unknown
- Experimental. Expect behavior to change in the future.
- Experimental. Expect behavior to change in the future.