SERVICE WORKERS
A service worker is a type of web worker that behaves like a proxy server inside the browser. Service workers allow you to intercept outgoing requests and cache the response. This allows a web page to work without network connectivity, as some or all of the page can potentially be served from the service worker cache. A service worker can also make use of the Notifications API, the Push API, the Background Sync API, and the Channel Messaging API.
Like shared workers, multiple pages on a single domain will all interact with a single service worker instance. However, to enable features such as the Push API, service workers can also survive the associated tab or browser being closed and wait for an incoming push event.
Ultimately, most developers will find that service workers are most useful for two primary tasks: acting as a caching layer for network requests, and enabling push notifications. In this sense, the service worker is a tool designed to enable web pages to behave...
