The onupdatefound property of the ServiceWorkerRegistration interface is an EventListener property called whenever an event of type statechange is fired; it is fired any time the ServiceWorkerRegistration.installing property acquires a new service worker. 
Note: This feature is available in Web Workers.
serviceWorkerRegistration.onupdatefound = function() { ... };
| Desktop | Mobile | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | WebView Android | Chrome Android | Firefox for Android | Opera Android | Safari on IOS | Samsung Internet | |
onupdatefound | 
40  | 
17  | 
 44 
Extended Support Releases (ESR) before Firefox 78 ESR do not support service workers and the Push API. 
 | 
No  | 
27  | 
11.1  | 
40  | 
40  | 
44  | 
27  | 
11.3  | 
4.0  | 
Promise
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    https://developer.mozilla.org/en-US/docs/Web/API/ServiceWorkerRegistration/onupdatefound