The FetchEvent() constructor creates a new FetchEvent object.


var fetchEvent = new FetchEvent(type, init);


A DOMString object specifying which event the object represents. This is always fetch for Fetch events.
init Optional

An object conforming to the FetchEventInit dictionary, containing options to apply to the event object. Options are as follows:

clientId Read only
The Client that the current service worker is controlling.
isReload Read only
A Boolean that signifies whether the page was reloaded or not when the event was dispatched. true if yes, and false if not. Typically, pressing the refresh button in a browser is a reload, while clicking a link and pressing the back button is not. If not present, it defaults to false.
preloadResponse Read only
A Promise which returns a previously-loaded response to the client.
replacesClientId Read only
A DOMString which identifies the client which is being replaced by resultingClientId.
resultingClientId Read only
A DOMString containing the new clientId if the client changes as a result of the page load.
request Read only
The Request object that would have triggered the event handler.


Specification Status Comment
Service Workers
The definition of 'FetchEvent() constructor' in that specification.
Working Draft Initial definition.

Browser compatibility

ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
FetchEvent() constructor
Chrome Full support 40Edge Full support ≤18Firefox Full support 44
Full support 44
Notes Extended Support Releases (ESR) before Firefox 78 ESR do not support service workers and the Push API.
IE No support NoOpera Full support 27Safari No support NoWebView Android Full support 40Chrome Android Full support 40Firefox Android Full support 44Opera Android Full support 27Safari iOS No support NoSamsung Internet Android Full support 4.0


Full support
Full support
No support
No support
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
See implementation notes.
See implementation notes.

See also