Note: This feature is only available in Service Workers.
The resultingClientId read-only property of the FetchEvent interface is the id of the client that replaces the previous client during a page navigation.
For example, when navigating from page A to page B resultingClientId is the ID of the client associated with page B.
If the fetch request is a subresource request or the request's destination is report, resultingClientId will be an empty string.
A string.
self.addEventListener("fetch", (event) => {
console.log(event.resultingClientId);
});