NavigationPreloadManager: getState() method

{{APIRef("Service Workers API")}}{{SecureContext_Header}}{{AvailableInWorkers}}

The getState() method of the {{domxref("NavigationPreloadManager")}} interface returns a {{jsxref("Promise")}} that resolves to an object with properties that indicate whether preload is enabled and what value will be sent in the {{HTTPHeader("Service-Worker-Navigation-Preload")}} HTTP header.

Syntax

getState()

Parameters

None.

Return value

A {{jsxref("Promise")}} that resolves with an object that has the following properties:

• enabled
  • : true if preloading is enabled, and false otherwise.
• headerValue
  • : A string containing the value that will be sent in the Service-Worker-Navigation-Preload HTTP header following a preloading {{domxref("Window/fetch", "fetch()")}}. This defaults to true unless the value was changed using {{domxref("NavigationPreloadManager.setHeaderValue()")}}.

Exceptions

• InvalidStateError {{domxref("DOMException")}}
  • : There is no active worker associated with the registration to which this {{domxref("NavigationPreloadManager")}} belongs.

Examples

The code below shows a request for the current state, made once the service worker is ready.

navigator.serviceWorker.ready
  .then((registration) => registration.navigationPreload.getState())
  .then((state) => {
    console.log(state.enabled); // boolean
    console.log(state.headerValue); // string
  })
  .catch((e) =>
    console.error(`NavigationPreloadManager not supported: ${e.message}`),
  );

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}