The ServiceWorker interface of the Service Worker API provides a reference to a service worker. Multiple browsing contexts (e.g. pages, workers, etc.) can be associated with the same service worker, each through a unique ServiceWorker object.
A ServiceWorker object is available in the ServiceWorkerRegistration.active property, and the ServiceWorkerContainer.controller property — this is a service worker that has been activated and is controlling the page (the service worker has been successfully registered, and the controlled page has been reloaded.)
The ServiceWorker interface is dispatched a set of lifecycle events — install and activate — and functional events including fetch. A ServiceWorker object has an associated ServiceWorker.state, related to its lifecycle.
The ServiceWorker interface inherits properties from its parent, Worker.
Returns the ServiceWorker serialized script URL defined as part of ServiceWorkerRegistration. The URL must be on the same origin as the document that registers the ServiceWorker.
Returns the state of the service worker. It returns one of the following values: installing, installed, activating, activated, or redundant.