ServiceWorkerState is associated with its ServiceWorker's state.ExtendableMessageEvent interface of the ServiceWorker API represents the event object of a message event fired on a service worker (when a channel message is received on the ServiceWorkerGlobalScope from another context) — extends the lifetime of such events.scope read-only property of the ServiceWorkerRegistration interface returns a unique identifier for a service worker registration. The service worker must be on the same origin as the document that registers the ServiceWorker.unregister method of the ServiceWorkerRegistration interface unregisters the service worker registration and returns a Promise. The promise will resolve to false if no registration was found, otherwise it resolves to true irrespective of whether unregistration happened or not (it may not unregister if someone else just called ServiceWorkerContainer.register with the same scope.) The service worker will finish any ongoing operations before it is unregistered.isReload read-only property of the FetchEvent interface returns true if the event was dispatched by the user attempting to reload the page, and false otherwise. Pressing the refresh button is a reload while clicking a link and pressing the back button is not.