In the following code snippet, we make a request to open a database, and include handlers for the success and error cases. For a full working example, see our To-do Notifications app (view example live.)
The parameter passed into the oninstall handler, the InstallEvent interface represents an install action that is dispatched on the ServiceWorkerGlobalScope of a ServiceWorker. As a child of ExtendableEvent, it ensures that functional events such as FetchEvent are not dispatched during installation. 
A service worker is an event-driven worker registered against an origin and a path. It takes the form of a JavaScript file that can control the web page/site it is associated with, intercepting and modifying navigation and resource requests, and caching resources in a very granular fashion to give you complete control over how your app behaves in certain situations (the most obvious one being when the network is not available.)
The ServiceWorker interface of the ServiceWorker 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.
The ServiceWorkerGlobalScope interface of the ServiceWorker API represents the global execution context of a service worker.
The ServiceWorkerMessageEvent interface of the ServiceWorker API contains information about an event sent to a ServiceWorkerContainer target. This extends the default message event to allow setting a ServiceWorker object as the source of a message. The event object is accessed via the handler function of a message event, when fired by a message received from a service worker.
The ServiceWorkerRegistion interface of the ServiceWorker API represents the service worker registration. You register a service worker to control one or more pages that share the same origin.
localStorage is the same as sessionStorage with the same same-origin rules applied but it is persistent. localStorage was introduced in Firefox 3.5.
The ExtendableEvent interface extends the lifetime of the install and activate events dispatched on the global scope as part of the service worker lifecycle. This ensures that any functional events (like FetchEvent) are not dispatched until it upgrades database schemas and deletes the outdated cache entries.
In the File System API, a FileException object represents error conditions that you might encounter while accessing the file system using the synchronous API. It extends the FileException interface described in File Writer and adds several new error codes.